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Witzany C, Regoes RR, Igler C. Assessing the relative importance of bacterial resistance, persistence and hyper-mutation for antibiotic treatment failure. Proc Biol Sci 2022; 289:20221300. [PMID: 36350213 PMCID: PMC9653239 DOI: 10.1098/rspb.2022.1300] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 10/18/2022] [Indexed: 08/01/2023] Open
Abstract
To curb the rising threat of antimicrobial resistance, we need to understand the routes to antimicrobial treatment failure. Bacteria can survive treatment by using both genetic and phenotypic mechanisms to diminish the effect of antimicrobials. We assemble empirical data showing that, for example, Pseudomonas aeruginosa infections frequently contain persisters, transiently non-growing cells unaffected by antibiotics (AB) and hyper-mutators, mutants with elevated mutation rates, and thus higher probability of genetic resistance emergence. Resistance, persistence and hyper-mutation dynamics are difficult to disentangle experimentally. Hence, we use stochastic population modelling and deterministic fitness calculations to investigate the relative importance of genetic and phenotypic mechanisms for immediate treatment failure and establishment of prolonged, chronic infections. We find that persistence causes 'hidden' treatment failure with very low cell numbers if antimicrobial concentrations prevent growth of genetically resistant cells. Persister cells can regrow after treatment is discontinued and allow for resistance evolution in the absence of AB. This leads to different mutational routes during treatment and relapse of an infection. By contrast, hyper-mutation facilitates resistance evolution during treatment, but rarely contributes to treatment failure. Our findings highlight the time and concentration dependence of different bacterial mechanisms to escape AB killing, which should be considered when designing 'failure-proof' treatments.
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Affiliation(s)
| | - Roland R. Regoes
- Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland
| | - Claudia Igler
- Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland
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2
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Hall KM, Pursell ZF, Morici LA. The role of the Pseudomonas aeruginosa hypermutator phenotype on the shift from acute to chronic virulence during respiratory infection. Front Cell Infect Microbiol 2022; 12:943346. [PMID: 35937684 PMCID: PMC9355025 DOI: 10.3389/fcimb.2022.943346] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 06/30/2022] [Indexed: 11/13/2022] Open
Abstract
Chronic respiratory infection (CRI) with Pseudomonas aeruginosa (Pa) presents many unique challenges that complicate treatment. One notable challenge is the hypermutator phenotype which is present in up to 60% of sampled CRI patient isolates. Hypermutation can be caused by deactivating mutations in DNA mismatch repair (MMR) genes including mutS, mutL, and uvrD. In vitro and in vivo studies have demonstrated hypermutator strains to be less virulent than wild-type Pa. However, patients colonized with hypermutators display poorer lung function and a higher incidence of treatment failure. Hypermutation and MMR-deficiency create increased genetic diversity and population heterogeneity due to elevated mutation rates. MMR-deficient strains demonstrate higher rates of mucoidy, a hallmark virulence determinant of Pa during CRI in cystic fibrosis patients. The mucoid phenotype results from simple sequence repeat mutations in the mucA gene made in the absence of functional MMR. Mutations in Pa are further increased in the absence of MMR, leading to microcolony biofilm formation, further lineage diversification, and population heterogeneity which enhance bacterial persistence and host immune evasion. Hypermutation facilitates the adaptation to the lung microenvironment, enabling survival among nutritional complexity and microaerobic or anaerobic conditions. Mutations in key acute-to-chronic virulence “switch” genes, such as retS, bfmS, and ampR, are also catalyzed by hypermutation. Consequently, strong positive selection for many loss-of-function pathoadaptive mutations is seen in hypermutators and enriched in genes such as lasR. This results in the characteristic loss of Pa acute infection virulence factors, including quorum sensing, flagellar motility, and type III secretion. Further study of the role of hypermutation on Pa chronic infection is needed to better inform treatment regimens against CRI with hypermutator strains.
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Affiliation(s)
- Kalen M. Hall
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA, United States
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Zachary F. Pursell
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Lisa A. Morici
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA, United States
- *Correspondence: Lisa A. Morici,
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3
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Polymicrobial infections can select against Pseudomonas aeruginosa mutators because of quorum-sensing trade-offs. Nat Ecol Evol 2022; 6:979-988. [PMID: 35618819 DOI: 10.1038/s41559-022-01768-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 04/13/2022] [Indexed: 11/08/2022]
Abstract
Bacteria with increased mutation rates (mutators) are common in chronic infections and are associated with poorer clinical outcomes, especially in the case of Pseudomonas aeruginosa infecting cystic fibrosis (CF) patients. There is, however, considerable between-patient variation in both P. aeruginosa mutator frequency and the composition of co-infecting pathogen communities. We investigated whether community context might affect selection of mutators. Using an in vitro CF model community, we show that P. aeruginosa mutators were favoured in the absence of other species but not in their presence. This was because there were trade-offs between adaptation to the biotic and abiotic environments (for example, loss of quorum sensing and associated toxin production was beneficial in the latter but not the former in our in vitro model community) limiting the evolvability advantage of an elevated mutation rate. Consistent with a role of co-infecting pathogens selecting against P. aeruginosa mutators in vivo, we show that the mutation frequency of P. aeruginosa population was negatively correlated with the frequency and diversity of co-infecting bacteria in CF infections. Our results suggest that co-infecting taxa can select against P. aeruginosa mutators, which may have potentially beneficial clinical consequences.
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4
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Armbruster CR, Marshall CW, Garber AI, Melvin JA, Zemke AC, Moore J, Zamora PF, Li K, Fritz IL, Manko CD, Weaver ML, Gaston JR, Morris A, Methé B, DePas WH, Lee SE, Cooper VS, Bomberger JM. Adaptation and genomic erosion in fragmented Pseudomonas aeruginosa populations in the sinuses of people with cystic fibrosis. Cell Rep 2021; 37:109829. [PMID: 34686349 PMCID: PMC8667756 DOI: 10.1016/j.celrep.2021.109829] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/09/2021] [Accepted: 09/22/2021] [Indexed: 10/20/2022] Open
Abstract
Pseudomonas aeruginosa notoriously adapts to the airways of people with cystic fibrosis (CF), yet how infection-site biogeography and associated evolutionary processes vary as lifelong infections progress remains unclear. Here we test the hypothesis that early adaptations promoting aggregation influence evolutionary-genetic trajectories by examining longitudinal P. aeruginosa from the sinuses of six adults with CF. Highly host-adapted lineages harbored mutator genotypes displaying signatures of early genome degradation associated with recent host restriction. Using an advanced imaging technique (MiPACT-HCR [microbial identification after passive clarity technique]), we find population structure tracks with genome degradation, with the most host-adapted, genome-degraded P. aeruginosa (the mutators) residing in small, sparse aggregates. We propose that following initial adaptive evolution in larger populations under strong selection for aggregation, P. aeruginosa persists in small, fragmented populations that experience stronger effects of genetic drift. These conditions enrich for mutators and promote degenerative genome evolution. Our findings underscore the importance of infection-site biogeography to pathogen evolution.
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Affiliation(s)
- Catherine R Armbruster
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | | | - Arkadiy I Garber
- Biodesign Center for Mechanisms of Evolution and School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA
| | - Jeffrey A Melvin
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Anna C Zemke
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - John Moore
- Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, PA 15219, USA
| | - Paula F Zamora
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Kelvin Li
- Center for Medicine and the Microbiome, University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA 15219, USA
| | - Ian L Fritz
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Christopher D Manko
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Madison L Weaver
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Jordan R Gaston
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Alison Morris
- Center for Medicine and the Microbiome, University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA 15219, USA
| | - Barbara Methé
- Center for Medicine and the Microbiome, University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA 15219, USA
| | - William H DePas
- Department of Pediatrics, Children's Hospital of Pittsburgh and University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Stella E Lee
- Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, PA 15219, USA.
| | - Vaughn S Cooper
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA; Center for Medicine and the Microbiome, University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA 15219, USA; Pittsburgh Center for Evolutionary Biology & Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
| | - Jennifer M Bomberger
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
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5
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Manos J. Current and Emerging Therapies to Combat Cystic Fibrosis Lung Infections. Microorganisms 2021; 9:1874. [PMID: 34576767 PMCID: PMC8466233 DOI: 10.3390/microorganisms9091874] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/26/2021] [Accepted: 08/30/2021] [Indexed: 11/30/2022] Open
Abstract
The ultimate aim of any antimicrobial treatment is a better infection outcome for the patient. Here, we review the current state of treatment for bacterial infections in cystic fibrosis (CF) lung while also investigating potential new treatments being developed to see how they may change the dynamics of antimicrobial therapy. Treatment with antibiotics coupled with regular physical therapy has been shown to reduce exacerbations and may eradicate some strains. Therapies such as hypertonic saline and inhaled PulmozymeTM (DNase-I) improve mucus clearance, while modifier drugs, singly and more successfully in combination, re-open certain mutant forms of the cystic fibrosis transmembrane conductance regulator (CFTR) to enable ion passage. No current method, however, completely eradicates infection, mainly due to bacterial survival within biofilm aggregates. Lung transplants increase lifespan, but reinfection is a continuing problem. CFTR modifiers normalise ion transport for the affected mutations, but there is conflicting evidence on bacterial clearance. Emerging treatments combine antibiotics with novel compounds including quorum-sensing inhibitors, antioxidants, and enzymes, or with bacteriophages, aiming to disrupt the biofilm matrix and improve antibiotic access. Other treatments involve bacteriophages that target, infect and kill bacteria. These novel therapeutic approaches are showing good promise in vitro, and a few have made the leap to in vivo testing.
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Affiliation(s)
- Jim Manos
- Infection, Immunity and Inflammation, Faculty of Medicine and Health, School of Medical Sciences, The University of Sydney, Sydney 2006, Australia
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6
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Abstract
Microbes are constantly evolving. Laboratory studies of bacterial evolution increase our understanding of evolutionary dynamics, identify adaptive changes, and answer important questions that impact human health. During bacterial infections in humans, however, the evolutionary parameters acting on infecting populations are likely to be much more complex than those that can be tested in the laboratory. Nonetheless, human infections can be thought of as naturally occurring in vivo bacterial evolution experiments, which can teach us about antibiotic resistance, pathogenesis, and transmission. Here, we review recent advances in the study of within-host bacterial evolution during human infection and discuss practical considerations for conducting such studies. We focus on 2 possible outcomes for de novo adaptive mutations, which we have termed "adapt-and-live" and "adapt-and-die." In the adapt-and-live scenario, a mutation is long lived, enabling its transmission on to other individuals, or the establishment of chronic infection. In the adapt-and-die scenario, a mutation is rapidly extinguished, either because it carries a substantial fitness cost, it arises within tissues that block transmission to new hosts, it is outcompeted by more fit clones, or the infection resolves. Adapt-and-die mutations can provide rich information about selection pressures in vivo, yet they can easily elude detection because they are short lived, may be more difficult to sample, or could be maladaptive in the long term. Understanding how bacteria adapt under each of these scenarios can reveal new insights about the basic biology of pathogenic microbes and could aid in the design of new translational approaches to combat bacterial infections.
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Affiliation(s)
- Matthew J. Culyba
- Department of Medicine, Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Center for Evolutionary Biology and Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Daria Van Tyne
- Department of Medicine, Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Center for Evolutionary Biology and Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
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7
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Deaconescu AM. Mfd - at the crossroads of bacterial DNA repair, transcriptional regulation and molecular evolvability. Transcription 2021; 12:156-170. [PMID: 34674614 PMCID: PMC8632110 DOI: 10.1080/21541264.2021.1982628] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/06/2021] [Accepted: 09/14/2021] [Indexed: 12/21/2022] Open
Abstract
For survival, bacteria need to continuously evolve and adapt to complex environments, including those that may impact the integrity of the DNA, the repository of genetic information to be passed on to future generations. The multiple factors of DNA repair share the substrate on which they operate with other key cellular machineries, principally those of replication and transcription, implying a high degree of coordination of DNA-based activities. In this review, I focus on progress made in the understanding of the protein factors operating at the crossroads of these three fundamental processes, with emphasis on the mutation frequency decline protein (Mfd, aka TRCF). Although Mfd research has a rich history that goes back in time for more than half a century, recent reports hint that much remains to be uncovered. I argue that besides being a transcription-repair coupling factor (TRCF), Mfd is also a global regulator of transcription and a pro-mutagenic factor, and that the way it interfaces with transcription, replication and nucleotide excision repair makes it an attractive candidate for the development of strategies to curb molecular evolution, hence, antibiotic resistance.
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Affiliation(s)
- Alexandra M. Deaconescu
- CONTACT Alexandra M. Deaconescu Molecular Biology, Cell Biology and Biochemistry, Laboratories of Molecular Medicine, Brown University, 70 Ship St. G-E4, Providence, RI02903, USA
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8
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Camus L, Vandenesch F, Moreau K. From genotype to phenotype: adaptations of Pseudomonas aeruginosa to the cystic fibrosis environment. Microb Genom 2021; 7:mgen000513. [PMID: 33529147 PMCID: PMC8190622 DOI: 10.1099/mgen.0.000513] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 12/21/2020] [Indexed: 12/12/2022] Open
Abstract
Pseudomonas aeruginosa is one of the main microbial species colonizing the lungs of cystic fibrosis patients and is responsible for the decline in respiratory function. Despite the hostile pulmonary environment, P. aeruginosa is able to establish chronic infections thanks to its strong adaptive capacity. Various longitudinal studies have attempted to compare the strains of early infection with the adapted strains of chronic infection. Thanks to new '-omics' techniques, convergent genetic mutations, as well as transcriptomic and proteomic dysregulations have been identified. As a consequence of this evolution, the adapted strains of P. aeruginosa have particular phenotypes that promote persistent infection.
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Affiliation(s)
- Laura Camus
- CIRI – Centre International de Recherche en Infectiologie, Université de Lyon/Inserm U1111/Université Claude Bernard Lyon 1/CNRS UMR5308/ENS de Lyon, Lyon, France
| | - François Vandenesch
- CIRI – Centre International de Recherche en Infectiologie, Université de Lyon/Inserm U1111/Université Claude Bernard Lyon 1/CNRS UMR5308/ENS de Lyon, Lyon, France
- Centre National de Référence des Staphylocoques, Hospices Civils de Lyon, Lyon, France
- Institut des Agents Infectieux, Hospices Civils de Lyon, Lyon, France
| | - Karen Moreau
- CIRI – Centre International de Recherche en Infectiologie, Université de Lyon/Inserm U1111/Université Claude Bernard Lyon 1/CNRS UMR5308/ENS de Lyon, Lyon, France
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9
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Liu H, Liu B, Zheng F, Chen X, Ye L, He Y. Distribution of pathogenic bacteria in lower respiratory tract infection in lung cancer patients after chemotherapy and analysis of integron resistance genes in respiratory tract isolates of uninfected patients. J Thorac Dis 2020; 12:4216-4223. [PMID: 32944333 PMCID: PMC7475539 DOI: 10.21037/jtd-20-928] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background We studied the distribution of pathogenic bacteria in lower respiratory tract infection in lung cancer patients after chemotherapy and analyzed the integron resistance genes in respiratory tract isolates of uninfected patients. Methods Retrospective analysis was used to select sputum samples from 400 lung cancer patients after chemotherapy admitted in Fuyang People’s Hospital from July 2017 to July 2019. Culture, isolation and identification of strains were conducted in accordance with the national clinical examination operating procedures. Results A total of 134 strains were identified. In 120 patients with pulmonary infection, 114 strains were cultured. Twenty strains of klebsiella pneumoniae were cultured in 280 patients without pulmonary infection. Among the 134 strains, the detection rate of gram-negative bacteria was 79.10%. The first four strains were Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Haemophilus influenzae. The gram-positive bacteria detection rate was 4.47%, mainly Staphylococcus aureus and Streptococcus. The fungus detection rate was 16.42%. The drug sensitivity results showed that the resistance rate of gram-negative bacillus to penicillin and cephalosporin was higher, and were more sensitive to carbapenem, piperacillin tazobactam and cefoperazone sulbactam. Gram-positive cocci were resistant to penicillin, macrolide and clindamycin, and sensitive to linezolid, vancomycin and rifampicin. All strains of fungal culture were candida albicans, which were sensitive to common antifungal drugs. Among the 20 strains of klebsiella pneumoniae cultured in sputum specimens of non-infected patients with lung cancer undergoing chemotherapy, 2 strains were integron-positive strains, and all of them were class I integrons. Conclusions Lung cancer patients after chemotherapy have a high resistance to commonly used antimicrobial drugs, so it is necessary to detect the resistance of pathogenic microorganisms in clinical practice. The strains carried by patients with lung cancer without pulmonary infection during chemotherapy can isolate type I integrons, suggesting that the spread of drug resistance at gene level should be closely detected.
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Affiliation(s)
- Haiyan Liu
- Department of Respiratory and Critical Care Medicine, Fuyang People's Hospital, Fuyang, China
| | - Bin Liu
- Department of Respiratory and Critical Care Medicine, Fuyang People's Hospital, Fuyang, China
| | - Fade Zheng
- Department of Respiratory and Critical Care Medicine, Fuyang People's Hospital, Fuyang, China
| | - Xiaoxia Chen
- Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University Medical School Cancer Institute, Tongji University School of Medicine, Shanghai, China
| | - Lingyun Ye
- Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University Medical School Cancer Institute, Tongji University School of Medicine, Shanghai, China
| | - Yayi He
- Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University Medical School Cancer Institute, Tongji University School of Medicine, Shanghai, China
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Hypermutator Pseudomonas aeruginosa Exploits Multiple Genetic Pathways To Develop Multidrug Resistance during Long-Term Infections in the Airways of Cystic Fibrosis Patients. Antimicrob Agents Chemother 2020; 64:AAC.02142-19. [PMID: 32071060 DOI: 10.1128/aac.02142-19] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 12/20/2019] [Indexed: 12/30/2022] Open
Abstract
Pseudomonas aeruginosa exploits intrinsic and acquired resistance mechanisms to resist almost every antibiotic used in chemotherapy. Antimicrobial resistance in P. aeruginosa isolates recovered from cystic fibrosis (CF) patients is further enhanced by the occurrence of hypermutator strains, a hallmark of chronic infections in CF patients. However, the within-patient genetic diversity of P. aeruginosa populations related to antibiotic resistance remains unexplored. Here, we show the evolution of the mutational resistome profile of a P. aeruginosa hypermutator lineage by performing longitudinal and transversal analyses of isolates collected from a CF patient throughout 20 years of chronic infection. Our results show the accumulation of thousands of mutations, with an overall evolutionary history characterized by purifying selection. However, mutations in antibiotic resistance genes appear to have been positively selected, driven by antibiotic treatment. Antibiotic resistance increased as infection progressed toward the establishment of a population constituted by genotypically diversified coexisting sublineages, all of which converged to multidrug resistance. These sublineages emerged by parallel evolution through distinct evolutionary pathways, which affected genes of the same functional categories. Interestingly, ampC and ftsI, encoding the β-lactamase and penicillin-binding protein 3, respectively, were found to be among the most frequently mutated genes. In fact, both genes were targeted by multiple independent mutational events, which led to a wide diversity of coexisting alleles underlying β-lactam resistance. Our findings indicate that hypermutators, apart from boosting antibiotic resistance evolution by simultaneously targeting several genes, favor the emergence of adaptive innovative alleles by clustering beneficial/compensatory mutations in the same gene, hence expanding P. aeruginosa strategies for persistence.
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11
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Liang Y, Zhang X, Yuan Y, Bao Y, Xiong M. Role and modulation of the secondary structure of antimicrobial peptides to improve selectivity. Biomater Sci 2020; 8:6858-6866. [PMID: 32815940 DOI: 10.1039/d0bm00801j] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Helix is a two-edged sword for AMPs, and conformational modulation of AMPs can control the balance between antimicrobial activity and toxicity.
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Affiliation(s)
- Yangbin Liang
- Guangzhou First People's Hospital
- School of Biomedical Sciences and Engineering
- South China University of Technology
- Guangzhou
- P. R. China
| | - Xinshuang Zhang
- Guangzhou First People's Hospital
- School of Biomedical Sciences and Engineering
- South China University of Technology
- Guangzhou
- P. R. China
| | - Yueling Yuan
- Guangzhou First People's Hospital
- School of Biomedical Sciences and Engineering
- South China University of Technology
- Guangzhou
- P. R. China
| | - Yan Bao
- Medical Research Center
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation
- Sun Yat-sen Memorial Hospital
- Sun Yat-sen University
- Guangzhou
| | - Menghua Xiong
- Guangzhou First People's Hospital
- School of Biomedical Sciences and Engineering
- South China University of Technology
- Guangzhou
- P. R. China
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12
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Epidemiology of Clonal Pseudomonas aeruginosa Infection in a Canadian Cystic Fibrosis Population. Ann Am Thorac Soc 2019; 15:827-836. [PMID: 29911888 DOI: 10.1513/annalsats.201801-007oc] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
RATIONALE The extent of the genetic relatedness among Pseudomonas aeruginosa isolates and its impact on clinical outcomes in the cystic fibrosis (CF) population is poorly understood. OBJECTIVES The objectives of this study were to determine the prevalence of clonal P. aeruginosa infection in Canada and to associate P. aeruginosa genotypes with clinical outcomes. METHODS This was an observational study of adult and pediatric patients with CF across Canada. Isolates were typed using multilocus sequence typing. A clone was defined as sharing at least six of seven alleles. Genotyping results were associated with clinical outcomes, including forced expiratory volume in 1 second, body mass index, rate of pulmonary exacerbation, and death/transplant. RESULTS A total of 1,537 P. aeruginosa isolates were genotyped to 403 unique sequence types (STs) in 402 individuals with CF. Although 39% of STs were shared, most were shared only among a small number of subjects, and the majority (79%) of the genetic diversity in P. aeruginosa isolates was observed between patients. There were no significant differences in clinical outcomes according to genotype. However, patients with a dynamic, changing ST infection pattern had both a steeper decline in forced expiratory volume in 1 second (-2.9% predicted change/yr, 95% confidence interval [CI] = -3.8 to -1.9 compared with 0.4, 95% CI = -0.3 to 1.0; P < 0.001) and body mass index (-1.0 percentile change/yr, 95% CI = -1.6 to -0.3 compared with -0.1, 95% CI = -0.7 to 0.5; P = 0.047) than those with a stable infection with the same ST. CONCLUSIONS There was no widespread sharing of dominant clones in our CF population, and the majority of the genetic diversity in P. aeruginosa was observed between patients. Changing genotypes over time within an individual was associated with worse clinical outcomes.
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13
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The Essential Role of Hypermutation in Rapid Adaptation to Antibiotic Stress. Antimicrob Agents Chemother 2019; 63:AAC.00744-19. [PMID: 31036684 DOI: 10.1128/aac.00744-19] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 04/19/2019] [Indexed: 12/22/2022] Open
Abstract
A common outcome of antibiotic exposure in patients and in vitro is the evolution of a hypermutator phenotype that enables rapid adaptation by pathogens. While hypermutation is a robust mechanism for rapid adaptation, it requires trade-offs between the adaptive mutations and the more common "hitchhiker" mutations that accumulate from the increased mutation rate. Using quantitative experimental evolution, we examined the role of hypermutation in driving the adaptation of Pseudomonas aeruginosa to colistin. Metagenomic deep sequencing revealed 2,657 mutations at ≥5% frequency in 1,197 genes and 761 mutations in 29 endpoint isolates. By combining genomic information, phylogenetic analyses, and statistical tests, we showed that evolutionary trajectories leading to resistance could be reliably discerned. In addition to known alleles such as pmrB, hypermutation allowed identification of additional adaptive alleles with epistatic relationships. Although hypermutation provided a short-term fitness benefit, it was detrimental to overall fitness. Alarmingly, a small fraction of the colistin-adapted population remained colistin susceptible and escaped hypermutation. In a clinical population, such cells could play a role in reestablishing infection upon withdrawal of colistin. We present here a framework for evaluating the complex evolutionary trajectories of hypermutators that applies to both current and emerging pathogen populations.
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14
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Giraudeau M, Sepp T, Ujvari B, Renaud F, Tasiemski A, Roche B, Capp JP, Thomas F. Differences in mutational processes and intra-tumour heterogeneity between organs: The local selective filter hypothesis. Evol Med Public Health 2019; 2019:139-146. [PMID: 31528343 PMCID: PMC6735757 DOI: 10.1093/emph/eoz017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 03/05/2019] [Indexed: 12/21/2022] Open
Abstract
Extensive diversity (genetic, cytogenetic, epigenetic and phenotypic) exists within and between tumours, but reasons behind these variations, as well as their consistent hierarchical pattern between organs, are poorly understood at the moment. We argue that these phenomena are, at least partially, explainable by the evolutionary ecology of organs' theory, in the same way that environmental adversity shapes mutation rates and level of polymorphism in organisms. Organs in organisms can be considered as specialized ecosystems that are, for ecological and evolutionary reasons, more or less efficient at suppressing tumours. When a malignancy does arise in an organ applying strong selection pressure on tumours, its constituent cells are expected to display a large range of possible surviving strategies, from hyper mutator phenotypes relying on bet-hedging to persist (high mutation rates and high diversity), to few poorly variable variants that become invisible to natural defences. In contrast, when tumour suppression is weaker, selective pressure favouring extreme surviving strategies is relaxed, and tumours are moderately variable as a result. We provide a comprehensive overview of this hypothesis. Lay summary: Different levels of mutations and intra-tumour heterogeneity have been observed between cancer types and organs. Anti-cancer defences are unequal between our organs. We propose that mostly aggressive neoplasms (i.e. higher mutational and ITH levels), succeed in emerging and developing in organs with strong defences.
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Affiliation(s)
- Mathieu Giraudeau
- CREEC, UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France
| | - Tuul Sepp
- Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu 51014, Estonia
| | - Beata Ujvari
- School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Waurn Ponds, Victoria 3216, Australia
| | - François Renaud
- CREEC, UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France
| | - Aurélie Tasiemski
- Université de Lille-sciences et technologies, UMR 8198 Evo-Eco-Paleo, Villeneuve d'Ascq/CNRS/INSERM/CHU Lille, Institut Pasteur de Lille, U1019-Unité Mixte de Recherche 8204, Lille, France
| | - Benjamin Roche
- CREEC, UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France
- IRD, Sorbonne Université, UMMISCO, F-93143, Bondy, France
- Departamento de Etología, Fauna Silvestre y Animales de Laboratorio, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), Ciudad de México, México
| | - Jean-Pascal Capp
- INSA/Université Fédérale de Toulouse, Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés, UMR CNRS 5504, UMR INRA 792, Toulouse, France
| | - Frédéric Thomas
- CREEC, UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France
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15
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Rees VE, Deveson Lucas DS, López-Causapé C, Huang Y, Kotsimbos T, Bulitta JB, Rees MC, Barugahare A, Peleg AY, Nation RL, Oliver A, Boyce JD, Landersdorfer CB. Characterization of Hypermutator Pseudomonas aeruginosa Isolates from Patients with Cystic Fibrosis in Australia. Antimicrob Agents Chemother 2019; 63:e02538-18. [PMID: 30745381 PMCID: PMC6437500 DOI: 10.1128/aac.02538-18] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Accepted: 01/27/2019] [Indexed: 12/22/2022] Open
Abstract
Hypermutable Pseudomonas aeruginosa isolates (hypermutators) have been identified in patients with cystic fibrosis (CF) and are associated with reduced lung function. Hypermutators display a greatly increased mutation rate and an enhanced ability to become resistant to antibiotics during treatment. Their prevalence has been established among patients with CF, but it has not been determined for patients with CF in Australia. This study aimed to determine the prevalence of hypermutable P. aeruginosa isolates from adult patients with CF from a health care institution in Australia and to characterize the genetic diversity and antibiotic susceptibility of these isolates. A total of 59 P. aeruginosa clinical isolates from patients with CF were characterized. For all isolates, rifampin (RIF) mutation frequencies and susceptibility to a range of antibiotics were determined. Of the 59 isolates, 13 (22%) were hypermutable. Whole-genome sequences were determined for all hypermutable isolates. Core genome polymorphisms were used to assess genetic relatedness of the isolates, both to each other and to a sample of previously characterized P. aeruginosa strains. Phylogenetic analyses showed that the hypermutators were from divergent lineages and that hypermutator phenotype was mostly the result of mutations in mutL or, less commonly, in mutS Hypermutable isolates also contained a range of mutations that are likely associated with adaptation of P. aeruginosa to the CF lung environment. Multidrug resistance was more prevalent in hypermutable than nonhypermutable isolates (38% versus 22%). This study revealed that hypermutable P. aeruginosa strains are common among isolates from patients with CF in Australia and are implicated in the emergence of antibiotic resistance.
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Affiliation(s)
- Vanessa E Rees
- Centre for Medicine Use and Safety, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria, Australia
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria, Australia
| | - Deanna S Deveson Lucas
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, Australia
| | - Carla López-Causapé
- Servicio de Microbiología, Hospital Universitario Son Espases, Instituto de Investigación Sanitaria de Palma, Palma de Mallorca, Spain
| | - Yuling Huang
- Centre for Medicine Use and Safety, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria, Australia
| | - Tom Kotsimbos
- Allergy, Immunology and Respiratory Medicine Department, Monash University, Melbourne, Victoria, Australia
| | - Jürgen B Bulitta
- Center for Pharmacometrics and Systems Pharmacology, College of Pharmacy, University of Florida, Florida, USA
| | | | - Adele Barugahare
- Monash Bioinformatics Platform, Monash University, Clayton, Victoria, Australia
| | - Anton Y Peleg
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, Australia
- Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Australia
| | - Roger L Nation
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria, Australia
| | - Antonio Oliver
- Servicio de Microbiología, Hospital Universitario Son Espases, Instituto de Investigación Sanitaria de Palma, Palma de Mallorca, Spain
| | - John D Boyce
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, Australia
| | - Cornelia B Landersdorfer
- Centre for Medicine Use and Safety, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria, Australia
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Victoria, Australia
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16
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Meropenem Combined with Ciprofloxacin Combats Hypermutable Pseudomonas aeruginosa from Respiratory Infections of Cystic Fibrosis Patients. Antimicrob Agents Chemother 2018; 62:AAC.01150-18. [PMID: 30104278 DOI: 10.1128/aac.01150-18] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 08/08/2018] [Indexed: 12/11/2022] Open
Abstract
Hypermutable Pseudomonas aeruginosa organisms are prevalent in chronic respiratory infections and have been associated with reduced lung function in cystic fibrosis (CF); these isolates can become resistant to all antibiotics in monotherapy. This study aimed to evaluate the time course of bacterial killing and resistance of meropenem and ciprofloxacin in combination against hypermutable and nonhypermutable P. aeruginosa Static concentration time-kill experiments over 72 h assessed meropenem and ciprofloxacin in mono- and combination therapies against PAO1 (nonhypermutable), PAOΔmutS (hypermutable), and hypermutable isolates CW8, CW35, and CW44 obtained from CF patients with chronic respiratory infections. Meropenem (1 or 2 g every 8 h [q8h] as 3-h infusions and 3 g/day as a continuous infusion) and ciprofloxacin (400 mg q8h as 1-h infusions) in monotherapies and combinations were further evaluated in an 8-day hollow-fiber infection model study (HFIM) against CW44. Concentration-time profiles in lung epithelial lining fluid reflecting the pharmacokinetics in CF patients were simulated and counts of total and resistant bacteria determined. All data were analyzed by mechanism-based modeling (MBM). In the HFIM, all monotherapies resulted in rapid regrowth with resistance at 48 h. The maximum daily doses of 6 g meropenem (T>MIC of 80% to 88%) and 1.2 g ciprofloxacin (area under the concentration-time curve over 24 h in the steady state divided by the MIC [AUC/MIC], 176), both given intermittently, in monotherapy failed to suppress regrowth and resulted in substantial emergence of resistance (≥7.6 log10 CFU/ml resistant populations). The combination of these regimens achieved synergistic killing and suppressed resistance. MBM with subpopulation and mechanistic synergy yielded unbiased and precise curve fits. Thus, the combination of 6 g/day meropenem plus ciprofloxacin holds promise for future clinical evaluation against infections by susceptible hypermutable P. aeruginosa.
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Epidemiology, Biology, and Impact of Clonal Pseudomonas aeruginosa Infections in Cystic Fibrosis. Clin Microbiol Rev 2018; 31:31/4/e00019-18. [PMID: 30158299 DOI: 10.1128/cmr.00019-18] [Citation(s) in RCA: 158] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Chronic lower airway infection with Pseudomonas aeruginosa is a major contributor to morbidity and mortality in individuals suffering from the genetic disease cystic fibrosis (CF). Whereas it was long presumed that each patient independently acquired unique strains of P. aeruginosa present in their living environment, multiple studies have since demonstrated that shared strains of P. aeruginosa exist among individuals with CF. Many of these shared strains, often referred to as clonal or epidemic strains, can be transmitted from one CF individual to another, potentially reaching epidemic status. Numerous epidemic P. aeruginosa strains have been described from different parts of the world and are often associated with an antibiotic-resistant phenotype. Importantly, infection with these strains often portends a worse prognosis than for infection with nonclonal strains, including an increased pulmonary exacerbation rate, exaggerated lung function decline, and progression to end-stage lung disease. This review describes the global epidemiology of clonal P. aeruginosa strains in CF and summarizes the current literature regarding the underlying biology and clinical impact of globally important CF clones. Mechanisms associated with patient-to-patient transmission are discussed, and best-evidence practices to prevent infections are highlighted. Preventing new infections with epidemic P. aeruginosa strains is of paramount importance in mitigating CF disease progression.
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18
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Optimization of a Meropenem-Tobramycin Combination Dosage Regimen against Hypermutable and Nonhypermutable Pseudomonas aeruginosa via Mechanism-Based Modeling and the Hollow-Fiber Infection Model. Antimicrob Agents Chemother 2018; 62:AAC.02055-17. [PMID: 29437610 DOI: 10.1128/aac.02055-17] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 01/24/2018] [Indexed: 12/19/2022] Open
Abstract
Hypermutable Pseudomonas aeruginosa strains are prevalent in patients with cystic fibrosis and rapidly become resistant to antibiotic monotherapies. Combination dosage regimens have not been optimized against such strains using mechanism-based modeling (MBM) and the hollow-fiber infection model (HFIM). The PAO1 wild-type strain and its isogenic hypermutable PAOΔmutS strain (MICmeropenem of 1.0 mg/liter and MICtobramycin of 0.5 mg/liter for both) were assessed using 96-h static-concentration time-kill studies (SCTK) and 10-day HFIM studies (inoculum, ∼108.4 CFU/ml). MBM of SCTK data were performed to predict expected HFIM outcomes. Regimens studied in the HFIM were meropenem at 1 g every 8 h (0.5-h infusion), meropenem at 3 g/day with continuous infusion, tobramycin at 10 mg/kg of body weight every 24 h (1-h infusion), and both combinations. Meropenem regimens delivered the same total daily dose. Time courses of total and less susceptible populations and MICs were determined. For the PAOΔmutS strain in the HFIM, all monotherapies resulted in rapid regrowth to >108.7 CFU/ml with near-complete replacement by less susceptible bacteria by day 3. Meropenem every 8 h with tobramycin caused >7-log10 bacterial killing followed by regrowth to >6 log10 CFU/ml by day 5 and high-level resistance (MICmeropenem, 32 mg/liter; MICtobramycin, 8 mg/liter). Continuous infusion of meropenem with tobramycin achieved >8-log10 bacterial killing without regrowth. For PAO1, meropenem monotherapies suppressed bacterial growth to <4 log10 over 7 to 9 days, with both combination regimens achieving near eradication. An MBM-optimized meropenem plus tobramycin regimen achieved synergistic killing and resistance suppression against a difficult-to-treat hypermutable P. aeruginosa strain. For the combination to be maximally effective, it was critical to achieve the optimal shape of the concentration-time profile for meropenem.
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Mensa J, Barberán J, Soriano A, Llinares P, Marco F, Cantón R, Bou G, del Castillo JG, Maseda E, Azanza JR, Pasquau J, García-Vidal C, Reguera JM, Sousa D, Gómez J, Montejo M, Borges M, Torres A, Alvarez-Lerma F, Salavert M, Zaragoza R, Oliver A. Antibiotic selection in the treatment of acute invasive infections by Pseudomonas aeruginosa: Guidelines by the Spanish Society of Chemotherapy. REVISTA ESPANOLA DE QUIMIOTERAPIA : PUBLICACION OFICIAL DE LA SOCIEDAD ESPANOLA DE QUIMIOTERAPIA 2018; 31:78-100. [PMID: 29480677 PMCID: PMC6159363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Pseudomonas aeruginosa is characterized by a notable intrinsic resistance to antibiotics, mainly mediated by the expression of inducible chromosomic β-lactamases and the production of constitutive or inducible efflux pumps. Apart from this intrinsic resistance, P. aeruginosa possess an extraordinary ability to develop resistance to nearly all available antimicrobials through selection of mutations. The progressive increase in resistance rates in P. aeruginosa has led to the emergence of strains which, based on their degree of resistance to common antibiotics, have been defined as multidrug resistant, extended-resistant and panresistant strains. These strains are increasingly disseminated worldwide, progressively complicating the treatment of P. aeruginosa infections. In this scenario, the objective of the present guidelines was to review and update published evidence for the treatment of patients with acute, invasive and severe infections caused by P. aeruginosa. To this end, mechanisms of intrinsic resistance, factors favoring development of resistance during antibiotic exposure, prevalence of resistance in Spain, classical and recently appeared new antibiotics active against P. aeruginosa, pharmacodynamic principles predicting efficacy, clinical experience with monotherapy and combination therapy, and principles for antibiotic treatment were reviewed to elaborate recommendations by the panel of experts for empirical and directed treatment of P. aeruginosa invasive infections.
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Affiliation(s)
- José Mensa
- Servicio de Enfermedades Infecciosas, Hospital Clinic, Barcelona, Spain
| | - José Barberán
- Servicio de Medicina Enfermedades infecciosas, Hospital Universitario HM Montepríncipe, Universidad San Pablo CEU. Madrid, Spain
| | - Alex Soriano
- Servicio de Enfermedades Infecciosas, Hospital Clinic, Barcelona, Spain
| | - Pedro Llinares
- Unidad de Enfermedades Infecciosas, Complejo Hospitalario Universitario A Coruña, Spain
| | - Francesc Marco
- Servicio de Microbiología, Hospital Clinic, Barcelona, Spain
| | - Rafael Cantón
- Servicio de Microbiología, Hospital Universitario Ramón y Cajal and Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS). Madrid, Spain
| | - German Bou
- Servicio de Microbiología, Complejo Hospitalario Universitario A Coruña, Spain
| | | | - Emilio Maseda
- Servicio de Anestesiología, Hospital Universitario La Paz, Madrid, Spain
| | - José Ramón Azanza
- Servicio de Farmacología, Clínica Universitaria de Navarra, Pamplona, Spain
| | - Juan Pasquau
- Servicio de Enfermedades Infecciosas, Hospital Universitario Virgen de la Nieves, Granada, Spain
| | | | - José María Reguera
- Servicio de Enfermedades Infecciosas, Hospital Universitario Carlos Haya, Málaga, Spain
| | - Dolores Sousa
- Unidad de Enfermedades Infecciosas, Complejo Hospitalario Universitario A Coruña, Spain
| | - Joaquín Gómez
- Servicio de Enfermedades Infecciosas, Hospital Clínico Universitario Virgen de la Arrixaca, Murcia, Spain
| | - Miguel Montejo
- Servicio de Enfermedades Infecciosas, Hospital Universitario Cruces, Bilbao, Spain
| | - Marcio Borges
- Servicio de Medicina Intensiva, Hospital Son Llátzer, Palma de Mallorca, Spain
| | - Antonio Torres
- Departamento de Neumología, Hospital Clinic, Barcelona, Spain
| | | | - Miguel Salavert
- Unidad de Enfermedades Infecciosas. Hospital Univeristario la Fe, Valencia, Spain
| | - Rafael Zaragoza
- Servicio de Medicina Intensiva, Hospital Universitario Dr. Peset, Valencia, Spain
| | - Antonio Oliver
- Servicio de Microbiología, Hospital Universitari Son Espases, Instituto de Investigación Sanitaria Illes Balears (idISBa), Palma de Mallorca, Spain
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20
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Boutin S, Weitnauer M, Hassel S, Graeber SY, Stahl M, Dittrich AS, Mall MA, Dalpke AH. One time quantitative PCR detection of Pseudomonas aeruginosa to discriminate intermittent from chronic infection in cystic fibrosis. J Cyst Fibros 2018; 17:348-355. [PMID: 29336943 DOI: 10.1016/j.jcf.2017.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 12/18/2017] [Accepted: 12/20/2017] [Indexed: 01/07/2023]
Abstract
BACKGROUND Chronic airway infection with Pseudomonas aeruginosa is a major risk factor of progression of lung disease in patients with cystic fibrosis (CF). Chronic P. aeruginosa infection evolves from intermittent infection that is amenable to antibiotic eradication, whereas chronically adapted P. aeruginosa becomes resistant to antibiotic therapy. Discrimination of intermittent versus chronic infection is therefore of high therapeutic relevance, yet the available diagnostic methods are only partly satisfactory. The aim of the present study was, therefore, to evaluate the usage of quantitative PCR (qPCR) to measure pathogen abundance and to discriminate between intermittent and chronic Pseudomonas infection in patients with CF. METHOD Using an established qPCR protocol, we analyzed the abundance of P. aeruginosa in 141 throats swabs and 238 sputa from CF patients with intermittent or chronic infection with P. aeruginosa, as determined by standard culture based diagnostics. RESULTS We observed a large increase of abundance of P. aeruginosa in throat swabs and sputum samples from patients with chronic compared to intermittent infections with P. aeruginosa. The data show that abundance of P. aeruginosa as measured by qPCR is a valuable tool to discriminate intermittent from chronic infection. Of note, P. aeruginosa burden seems more sensitive than mucoidity phenotype to discriminate chronic from intermittent strains. Furthermore we observed that molecular detection in throat swabs was linked to a viable culture in the sputum when sputum was available. This result is of special interest in young patients with cystic fibrosis that often cannot expectorate sputum. We also observed that qPCR in comparison to culture detected the infection earlier. CONCLUSION The results suggest that qPCR detection and quantification of P. aeruginosa is a precious tool to be added to the diagnostic toolbox in cystic fibrosis.
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Affiliation(s)
- Sébastien Boutin
- Department of Infectious Disease, Medical Microbiology and Hygiene, University Hospital Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Michael Weitnauer
- Department of Infectious Disease, Medical Microbiology and Hygiene, University Hospital Heidelberg, Germany
| | - Selina Hassel
- Department of Infectious Disease, Medical Microbiology and Hygiene, University Hospital Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Simon Y Graeber
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics, University of Heidelberg, Heidelberg, Germany; Department of Translational Pulmonology, University of Heidelberg, Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Mirjam Stahl
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics, University of Heidelberg, Heidelberg, Germany; Department of Translational Pulmonology, University of Heidelberg, Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - A Susanne Dittrich
- Department of Translational Pulmonology, University of Heidelberg, Heidelberg, Germany; Department of Pneumology and Critical Care Medicine, Thoraxklinik at the University Hospital Heidelberg, Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Marcus A Mall
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics, University of Heidelberg, Heidelberg, Germany; Department of Translational Pulmonology, University of Heidelberg, Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Alexander H Dalpke
- Department of Infectious Disease, Medical Microbiology and Hygiene, University Hospital Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany.
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21
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Using experimental evolution to identify druggable targets that could inhibit the evolution of antimicrobial resistance. J Antibiot (Tokyo) 2017; 71:279-286. [PMID: 28928474 PMCID: PMC5788704 DOI: 10.1038/ja.2017.108] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 07/27/2017] [Accepted: 08/05/2017] [Indexed: 02/05/2023]
Abstract
With multi-drug and pan-drug-resistant bacteria becoming increasingly common in hospitals, antibiotic resistance has threatened to return us to a pre-antibiotic era that would completely undermine modern medicine. There is an urgent need to develop new antibiotics and strategies to combat resistance that are substantially different from earlier drug discovery efforts. One such strategy that would complement current and future antibiotics would be a class of co-drugs that target the evolution of resistance and thereby extend the efficacy of specific classes of antibiotics. A critical step in the development of such strategies lies in understanding the critical evolutionary trajectories responsible for resistance and which proteins or biochemical pathways within those trajectories would be good candidates for co-drug discovery. We identify the most important steps in the evolution of resistance for a specific pathogen and antibiotic combination by evolving highly polymorphic populations of pathogens to resistance in a novel bioreactor that favors biofilm development. As the populations evolve to increasing drug concentrations, we use deep sequencing to elucidate the network of genetic changes responsible for resistance and subsequent in vitro biochemistry and often structure determination to determine how the adaptive mutations produce resistance. Importantly, the identification of the molecular steps, their frequency within the populations and their chronology within the evolutionary trajectory toward resistance is critical to assessing their relative importance. In this work, we discuss findings from the evolution of the ESKAPE pathogen, Pseudomonas aeruginosa to the drug of last resort, colistin to illustrate the power of this approach.
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A Low-Molecular-Weight Alginate Oligosaccharide Disrupts Pseudomonal Microcolony Formation and Enhances Antibiotic Effectiveness. Antimicrob Agents Chemother 2017. [PMID: 28630204 DOI: 10.1128/aac.00762-17] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In chronic respiratory disease, the formation of dense, 3-dimensional "microcolonies" by Pseudomonas aeruginosa within the airway plays an important role in contributing to resistance to treatment. An in vitro biofilm model of pseudomonal microcolony formation using artificial-sputum (AS) medium was established to study the effects of low-molecular-weight alginate oligomers (OligoG CF-5/20) on pseudomonal growth, microcolony formation, and the efficacy of colistin. The studies employed clinical cystic fibrosis (CF) isolates (n = 3) and reference nonmucoid and mucoid multidrug-resistant (MDR) CF isolates (n = 7). Bacterial growth and biofilm development and disruption were studied using cell viability assays and image analysis with scanning electron and confocal laser scanning microscopy. Pseudomonal growth in AS medium was associated with increased ATP production (P < 0.05) and the formation (at 48 h) of discrete (>10-μm) microcolonies. In conventional growth medium, colistin retained an ability to inhibit growth of planktonic bacteria, although the MIC was increased (0.1 to 0.4 μg/ml) in AS medium compared to Mueller-Hinton (MH) medium. In contrast, in an established-biofilm model in AS medium, the efficacy of colistin was decreased. OligoG CF-5/20 (≥2%) treatment, however, induced dose-dependent biofilm disruption (P < 0.05) and led to colistin retaining its antimicrobial activity (P < 0.05). While circular dichroism indicated that OligoG CF-5/20 did not change the orientation of the alginate carboxyl groups, mass spectrometry demonstrated that the oligomers induced dose-dependent (>0.2%; P < 0.05) reductions in pseudomonal quorum-sensing signaling. These findings reinforce the potential clinical significance of microcolony formation in the CF lung and highlight a novel approach to treat MDR pseudomonal infections.
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23
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Smith WD, Bardin E, Cameron L, Edmondson CL, Farrant KV, Martin I, Murphy RA, Soren O, Turnbull AR, Wierre-Gore N, Alton EW, Bundy JG, Bush A, Connett GJ, Faust SN, Filloux A, Freemont PS, Jones AL, Takats Z, Webb JS, Williams HD, Davies JC. Current and future therapies for Pseudomonas aeruginosa infection in patients with cystic fibrosis. FEMS Microbiol Lett 2017; 364:3868374. [DOI: 10.1093/femsle/fnx121] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 06/12/2017] [Indexed: 12/12/2022] Open
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Deiham B, Douraghi M, Adibhesami H, Yaseri M, Rahbar M. Screening of mutator phenotype in clinical strains of Acinetobacter baumannii. Microb Pathog 2017; 104:175-179. [PMID: 28111327 DOI: 10.1016/j.micpath.2017.01.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 01/12/2017] [Accepted: 01/18/2017] [Indexed: 11/30/2022]
Abstract
To our knowledge, no study has considered the growing colonies of A. baumannii in the inhibition zone of antibiotic disks as an indication of mutator. Here, we screened the mutator phenotype in a large series of clinical strains of A. baumannii. A collection of 300 strains were tested for antibiotic susceptibility and yielding colonies in the inhibition zone of antibiotic disks. The mutation frequency (MF) of strains was determined using rifampicin screen agar (300 μg/mL). Among strains tested, 180 had colonies in the inhibition zone of at least one or more than one (≤7) antibiotic. Sixty strains also generated mutant colonies on rifampicin screen agar with MF mean of 4.9 × 10-9. One strain was found with 59-fold (2.9 × 10-7) increase of MF than the mean value, only yielded colonies in the inhibition zone of imipenem, and classified as strong mutator or hypermutator. The MF ranged from 1 × 10-12 to 6.6 × 10-10 in remaining strains (n = 59), corresponded to non-mutator phenotype. There was a significant correlation between the number of colonies that grew in inhibition zone of amikacin disk and MF (P = 0.002). We showed that mutator phenotype emerged among clinical strains of A. baumannii as expected frequency in other bacterial species from non-chronic infections. This study revealed that wide screening of strains yielding colonies in the inhibition zone of antibiotics can be utilized to identify mutators. The mutant colonies need to be considered as a subpopulation of bacteria that may affect the interpretation of antibiotic susceptibility testing and consequently lead to treatment failure.
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Affiliation(s)
- Behnaz Deiham
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Masoumeh Douraghi
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran; Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran.
| | - Habibeh Adibhesami
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Mehdi Yaseri
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Rahbar
- Department of Microbiology, Reference Health Laboratories, Ministry of Health, Tehran, Iran
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25
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Davies EV, James CE, Brockhurst MA, Winstanley C. Evolutionary diversification of Pseudomonas aeruginosa in an artificial sputum model. BMC Microbiol 2017; 17:3. [PMID: 28056789 PMCID: PMC5216580 DOI: 10.1186/s12866-016-0916-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 12/15/2016] [Indexed: 12/20/2022] Open
Abstract
Background During chronic lung infections of cystic fibrosis patients Pseudomonas aeruginosa populations undergo extensive evolutionary diversification. However, the selective drivers of this evolutionary process are poorly understood. To test the effects of temperate phages on diversification in P. aeruginosa biofilms we experimentally evolved populations of P. aeruginosa for approximately 240 generations in artificial sputum medium with or without a community of three temperate phages. Results Analysis of end-point populations using a suite of phenotypic tests revealed extensive phenotypic diversification within populations, but no significant differences between the populations evolved with or without phages. The most common phenotypic variant observed was loss of all three types of motility (swimming, swarming and twitching) and resistance to all three phages. Despite the absence of selective pressure, some members of the population evolved antibiotic resistance. The frequency of antibiotic resistant isolates varied according to population and the antibiotic tested. However, resistance to ceftazidime and tazobactam-piperacillin was observed more frequently than resistance to other antibiotics, and was associated with higher prevelence of isolates exhibiting a hypermutable phenotype and increased beta-lactamase production. Conclusions We observed considerable within-population phenotypic diversity in P. aeruginosa populations evolving in the artificial sputum medium biofilm model. Replicate populations evolved both in the presence and absence of phages converged upon similar sets of phenotypes. The evolved phenotypes, including antimicrobial resistance, were similar to those observed amongst clinical isolates from cystic fibrosis infections. Electronic supplementary material The online version of this article (doi:10.1186/s12866-016-0916-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Emily V Davies
- Institute of Infection and Global Health, University of Liverpool, 8 West Derby Street, Liverpool, L69 7BE, UK
| | - Chloe E James
- Institute of Infection and Global Health, University of Liverpool, 8 West Derby Street, Liverpool, L69 7BE, UK.,School of Environment and Life Sciences, University of Salford, Manchester, M5 4WT, UK
| | | | - Craig Winstanley
- Institute of Infection and Global Health, University of Liverpool, 8 West Derby Street, Liverpool, L69 7BE, UK.
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Marvig RL, Dolce D, Sommer LM, Petersen B, Ciofu O, Campana S, Molin S, Taccetti G, Johansen HK. Within-host microevolution of Pseudomonas aeruginosa in Italian cystic fibrosis patients. BMC Microbiol 2015; 15:218. [PMID: 26482905 PMCID: PMC4612410 DOI: 10.1186/s12866-015-0563-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 10/12/2015] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Chronic infection with Pseudomonas aeruginosa is a major cause of morbidity and mortality in cystic fibrosis (CF) patients, and a more complete understanding of P. aeruginosa within-host genomic evolution, transmission, and population genomics may provide a basis for improving intervention strategies. Here, we report the first genomic analysis of P. aeruginosa isolates sampled from Italian CF patients. RESULTS By genome sequencing of 26 isolates sampled over 19 years from four patients, we elucidated the within-host evolution of clonal lineages in each individual patient. Many of the identified mutations were located in pathoadaptive genes previously associated with host adaptation, and we correlated mutations with changes in CF-relevant phenotypes such as antibiotic resistance. In addition, the genomic analysis revealed that three patients shared the same clone. Furthermore, we compared the genomes of the Italian CF isolates to a panel of genome sequenced strains of P. aeruginosa from other countries. Isolates from two of the Italian lineages belonged to clonal complexes of P. aeruginosa that have previously been identified in Danish CF patients, and our genomic comparison showed that clonal isolates from the same country may be more distantly related than clonal isolates from different countries. CONCLUSIONS This is the first whole-genome analysis of P. aeruginosa isolated from Italian CF patients, and together with both phenotypic and clinical information this dataset facilitates a more detailed understanding of P. aeruginosa within-host genomic evolution, transmission, and population genomics. We conclude that the evolution of the Italian lineages resembles what has been found in other countries.
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Affiliation(s)
- Rasmus Lykke Marvig
- Department of Immunology and Microbiology, Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. .,Center for Genomic Medicine, Rigshospitalet, Copenhagen, Denmark.
| | - Daniela Dolce
- Department of Paediatric Medicine, Cystic Fibrosis Centre, Anna Meyer Children's University Hospital, Florence, Italy.
| | - Lea M Sommer
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark. .,The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
| | - Bent Petersen
- Center for Biological Sequence Analysis, Technical University of Denmark, Lyngby, Denmark.
| | - Oana Ciofu
- Department of Immunology and Microbiology, Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Silvia Campana
- Department of Paediatric Medicine, Cystic Fibrosis Centre, Anna Meyer Children's University Hospital, Florence, Italy.
| | - Søren Molin
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark. .,The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
| | - Giovanni Taccetti
- Department of Paediatric Medicine, Cystic Fibrosis Centre, Anna Meyer Children's University Hospital, Florence, Italy.
| | - Helle Krogh Johansen
- Department of Immunology and Microbiology, Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. .,The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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Evans TJ. Small colony variants of Pseudomonas aeruginosa in chronic bacterial infection of the lung in cystic fibrosis. Future Microbiol 2015; 10:231-9. [PMID: 25689535 DOI: 10.2217/fmb.14.107] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Pseudomonas aeruginosa is the most common pathogen that colonizes the lungs of patients with cystic fibrosis. Isolates from sputum are typically all derived from the same strain of bacterium but show extensive phenotypic heterogeneity. One of these variants is the so-called small colony variant, which also shows increased ability to form a biofilm and is frequently resistant to multiple antibiotics. The presence of small colony variants in the sputum of patients with cystic fibrosis is associated with a worse clinical condition. The underlying mechanism responsible for generation of the small colony phenotype remains unclear, but a final common pathway would appear to be elevation of intracellular levels of cyclic di-GMP. This phenotypic variant is thus not just a laboratory curiosity, but a significant bacterial adaptation that favors survival within the lung of patients with cystic fibrosis and contributes to the pulmonary damage caused by P. aeruginosa.
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28
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Oliver A. Clinical relevance of Pseudomonas aeruginosa hypermutation in cystic fibrosis chronic respiratory infection. J Cyst Fibros 2015; 14:e1-2. [DOI: 10.1016/j.jcf.2014.12.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 12/05/2014] [Indexed: 11/15/2022]
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Marvig RL, Sommer LM, Jelsbak L, Molin S, Johansen HK. Evolutionary insight from whole-genome sequencing of Pseudomonas aeruginosa from cystic fibrosis patients. Future Microbiol 2015; 10:599-611. [DOI: 10.2217/fmb.15.3] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa causes chronic airway infections in patients with cystic fibrosis (CF), and it is directly associated with the morbidity and mortality connected with this disease. The ability of P. aeruginosa to establish chronic infections in CF patients is suggested to be due to the large genetic repertoire of P. aeruginosa and its ability to genetically adapt to the host environment. Here, we review the recent work that has applied whole-genome sequencing to understand P. aeruginosa population genomics, within-host microevolution and diversity, mutational mechanisms, genetic adaptation and transmission events. Finally, we summarize the advances in relation to medical applications and laboratory evolution experiments.
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Affiliation(s)
| | - Lea M Sommer
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark
| | - Lars Jelsbak
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Søren Molin
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark
| | - Helle Krogh Johansen
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark
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Convergent evolution and adaptation of Pseudomonas aeruginosa within patients with cystic fibrosis. Nat Genet 2014; 47:57-64. [DOI: 10.1038/ng.3148] [Citation(s) in RCA: 404] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 10/27/2014] [Indexed: 12/30/2022]
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Coexistence and within-host evolution of diversified lineages of hypermutable Pseudomonas aeruginosa in long-term cystic fibrosis infections. PLoS Genet 2014; 10:e1004651. [PMID: 25330091 PMCID: PMC4199492 DOI: 10.1371/journal.pgen.1004651] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 08/03/2014] [Indexed: 12/14/2022] Open
Abstract
The advent of high-throughput sequencing techniques has made it possible to follow the genomic evolution of pathogenic bacteria by comparing longitudinally collected bacteria sampled from human hosts. Such studies in the context of chronic airway infections by Pseudomonas aeruginosa in cystic fibrosis (CF) patients have indicated high bacterial population diversity. Such diversity may be driven by hypermutability resulting from DNA mismatch repair system (MRS) deficiency, a common trait evolved by P. aeruginosa strains in CF infections. No studies to date have utilized whole-genome sequencing to investigate within-host population diversity or long-term evolution of mutators in CF airways. We sequenced the genomes of 13 and 14 isolates of P. aeruginosa mutator populations from an Argentinian and a Danish CF patient, respectively. Our collection of isolates spanned 6 and 20 years of patient infection history, respectively. We sequenced 11 isolates from a single sample from each patient to allow in-depth analysis of population diversity. Each patient was infected by clonal populations of bacteria that were dominated by mutators. The in vivo mutation rate of the populations was ∼100 SNPs/year–∼40-fold higher than rates in normo-mutable populations. Comparison of the genomes of 11 isolates from the same sample showed extensive within-patient genomic diversification; the populations were composed of different sub-lineages that had coexisted for many years since the initial colonization of the patient. Analysis of the mutations identified genes that underwent convergent evolution across lineages and sub-lineages, suggesting that the genes were targeted by mutation to optimize pathogenic fitness. Parallel evolution was observed in reduction of overall catabolic capacity of the populations. These findings are useful for understanding the evolution of pathogen populations and identifying new targets for control of chronic infections. Patients with cystic fibrosis (CF) are often colonized by a single clone of the common, widespread bacterium Pseudomonas aeruginosa, resulting in chronic airway infections. Long-term persistence of the bacteria involves the emergence and selection of multiple phenotypic variants. Among these are “mutator” variants characterized by increased mutation rates resulting from the inactivation of DNA repair systems. The genetic evolution of mutators during the course of chronic infection is poorly understood, and the effects of hypermutability on bacterial population structure have not been studied using genomic approaches. We evaluated the genomic changes undergone by mutator populations of P. aeruginosa obtained from single sputum samples from two chronically infected CF patients, and found that mutators completely dominated the infecting population in both patients. These populations displayed high genomic diversity based on vast accumulation of stochastic mutations. Our results are in contrast to the concept of a homogeneous population consisting of a single dominant clone; rather, they support a model of populations structured by diverse subpopulations that coexist within the patient. Certain genes involved in adaptation were highly and convergently mutated in both lineages, suggesting that these genes were beneficial and potentially responsible for the co-selection of mutator alleles.
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Auerbach A, Kerem E, Assous MV, Picard E, Bar-Meir M. Is infection with hypermutable Pseudomonas aeruginosa clinically significant? J Cyst Fibros 2014; 14:347-52. [PMID: 25308183 DOI: 10.1016/j.jcf.2014.09.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 09/15/2014] [Accepted: 09/17/2014] [Indexed: 10/24/2022]
Abstract
BACKGROUND Hypermutable Pseudomonas aeruginosa (HPA) with high mutation rate due to defects in the DNA mismatch repair genes are frequently isolated in the sputum of cystic fibrosis (CF) patients. These isolates tend to be multidrug resistant and may be better adapted to the CF lung environment. However, the clinical significance of this infection has not been determined. METHODS This prospective study enrolled patients with PA infection attending CF clinics in Jerusalem between 2010 and 2011. Mutation frequency of pseudomonas isolates was determined by quantification of colonies resistant to rifampicin. RESULTS Of the 73 patients enrolled, 22 (30%) were infected with HPA. Average mutation frequency was 2.95×10(-4) in HPA and 1×10(-7) in non-HPA. Pulmonary function tests, number of pulmonary exacerbations and the response to antibiotic therapy were similar between patients infected with HPA and non-HPA isolates. The only predictors for infection with HPA were resistance to multiple antimicrobial categories (OR=4.8, 95% CI: 1.8-12.4) and previous use of inhaled colistin (OR=8.1, 95% CI: 2-30). Resistant mutant subpopulation analysis was a poor screening test for identifying HPA isolates. CONCLUSIONS Infection with hypermutable strains represents the marked ability of PA to adapt to the lung environment, but was not associated with worse clinical outcome.
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Affiliation(s)
- Adi Auerbach
- Pediatric Department, Shaare-Zedek Medical Center, Jerusalem, Israel
| | - Eitan Kerem
- Pediatric Department, Cystic Fibrosis Center, Hadassah Hebrew University Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University Hadassah Medical School, Jerusalem, Israel
| | | | - Elie Picard
- Pediatric Department, Shaare-Zedek Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University Hadassah Medical School, Jerusalem, Israel
| | - Maskit Bar-Meir
- Pediatric Department, Shaare-Zedek Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University Hadassah Medical School, Jerusalem, Israel.
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Oglesby-Sherrouse AG, Djapgne L, Nguyen AT, Vasil AI, Vasil ML. The complex interplay of iron, biofilm formation, and mucoidy affecting antimicrobial resistance of Pseudomonas aeruginosa. Pathog Dis 2014; 70:307-20. [PMID: 24436170 DOI: 10.1111/2049-632x.12132] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 12/20/2013] [Accepted: 01/02/2014] [Indexed: 11/29/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic bacterial pathogen that is refractory to a variety of current antimicrobial therapeutic regimens. Complicating treatment for such infections is the ability of P. aeruginosa to form biofilms, as well as several innate and acquired resistance mechanisms. Previous studies suggest iron plays a role in resistance to antimicrobial therapy, including the efficacy of an FDA-approved iron chelator, deferasirox (DSX), or Gallium, an iron analog, in potentiating antibiotic-dependent killing of P. aeruginosa biofilms. Here, we show that iron-replete conditions enhance resistance of P. aeruginosa nonbiofilm growth against tobramycin and tigecycline. Interestingly, the mechanism of iron-enhanced resistance to each of these antibiotics is distinct. Whereas pyoverdine-mediated iron uptake is important for optimal resistance to tigecycline, it does not enhance tobramycin resistance. In contrast, heme supplementation results in increased tobramycin resistance, while having no significant effect on tigecycline resistance. Thus, nonsiderophore bound iron plays an important role in resistance to tobramycin, while pyoverdine increases the ability of P. aeruginosa to resist tigecycline treatment. Lastly, we show that iron increases the minimal concentration of tobramycin, but not tigecycline, required to eradicate P. aeruginosa biofilms. Moreover, iron depletion blocks the previous observed induction of biofilm formation by subinhibitory concentrations of tobramycin, suggesting iron and tobramycin signal through overlapping regulatory pathways to affect biofilm formation. These data further support the role of iron in P. aeruginosa antibiotic resistance, providing yet another compelling case for targeting iron acquisition for future antimicrobial drug development.
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Affiliation(s)
- Amanda G Oglesby-Sherrouse
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD, USA; Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, MD, USA
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O'Brien S, Rodrigues AMM, Buckling A. The evolution of bacterial mutation rates under simultaneous selection by interspecific and social parasitism. Proc Biol Sci 2013; 280:20131913. [PMID: 24197408 PMCID: PMC3826219 DOI: 10.1098/rspb.2013.1913] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 10/09/2013] [Indexed: 02/05/2023] Open
Abstract
Many bacterial populations harbour substantial numbers of hypermutable bacteria, in spite of hypermutation being associated with deleterious mutations. One reason for the persistence of hypermutators is the provision of novel mutations, enabling rapid adaptation to continually changing environments, for example coevolving virulent parasites. However, hypermutation also increases the rate at which intraspecific parasites (social cheats) are generated. Interspecific and intraspecific parasitism are therefore likely to impose conflicting selection pressure on mutation rate. Here, we combine theory and experiments to investigate how simultaneous selection from inter- and intraspecific parasitism affects the evolution of bacterial mutation rates in the plant-colonizing bacterium Pseudomonas fluorescens. Both our theoretical and experimental results suggest that phage presence increases and selection for public goods cooperation (the production of iron-scavenging siderophores) decreases selection for mutator bacteria. Moreover, phages imposed a much greater growth cost than social cheating, and when both selection pressures were imposed simultaneously, selection for cooperation did not affect mutation rate evolution. Given the ubiquity of infectious phages in the natural environment and clinical infections, our results suggest that phages are likely to be more important than social interactions in determining mutation rate evolution.
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Affiliation(s)
- Siobhán O'Brien
- Department of Biosciences, University of Exeter, Tremough, Penryn, Cornwall TR10 9EZ, UK
| | | | - Angus Buckling
- Department of Biosciences, University of Exeter, Tremough, Penryn, Cornwall TR10 9EZ, UK
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35
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Marvig RL, Johansen HK, Molin S, Jelsbak L. Genome analysis of a transmissible lineage of pseudomonas aeruginosa reveals pathoadaptive mutations and distinct evolutionary paths of hypermutators. PLoS Genet 2013; 9:e1003741. [PMID: 24039595 PMCID: PMC3764201 DOI: 10.1371/journal.pgen.1003741] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/08/2013] [Indexed: 11/18/2022] Open
Abstract
Genome sequencing of bacterial pathogens has advanced our understanding of their evolution, epidemiology, and response to antibiotic therapy. However, we still have only a limited knowledge of the molecular changes in in vivo evolving bacterial populations in relation to long-term, chronic infections. For example, it remains unclear what genes are mutated to facilitate the establishment of long-term existence in the human host environment, and in which way acquisition of a hypermutator phenotype with enhanced rates of spontaneous mutations influences the evolutionary trajectory of the pathogen. Here we perform a retrospective study of the DK2 clone type of P. aeruginosa isolated from Danish patients suffering from cystic fibrosis (CF), and analyze the genomes of 55 bacterial isolates collected from 21 infected individuals over 38 years. Our phylogenetic analysis of 8,530 mutations in the DK2 genomes shows that the ancestral DK2 clone type spread among CF patients through several independent transmission events. Subsequent to transmission, sub-lineages evolved independently for years in separate hosts, creating a unique possibility to study parallel evolution and identification of genes targeted by mutations to optimize pathogen fitness (pathoadaptive mutations). These genes were related to antibiotic resistance, the cell envelope, or regulatory functions, and we find that the prevalence of pathoadaptive mutations correlates with evolutionary success of co-evolving sub-lineages. The long-term co-existence of both normal and hypermutator populations enabled comparative investigations of the mutation dynamics in homopolymeric sequences in which hypermutators are particularly prone to mutations. We find a positive exponential correlation between the length of the homopolymer and its likelihood to acquire mutations and identify two homopolymer-containing genes preferentially mutated in hypermutators. This homopolymer facilitated differential mutagenesis provides a novel genome-wide perspective on the different evolutionary trajectories of hypermutators, which may help explain their emergence in CF infections. Pseudomonas aeruginosa is the dominating pathogen of chronic airway infections in patients with cystic fibrosis (CF). Although bacterial long-term persistence in CF hosts involves mutation and selection of genetic variants with increased fitness in the CF lung environment, our understanding of the within-host evolutionary processes is limited. Here, we performed a retrospective study of the P. aeruginosa DK2 clone type, which is a transmissible clone isolated from chronically infected Danish CF patients over a period of 38 years. Whole-genome analysis of DK2 isolates enabled a fine-grained reconstruction of the recent evolutionary history of the DK2 lineage and an identification of bacterial genes targeted by mutations to optimize pathogen fitness. The identification of such pathoadaptive genes gives new insight into how the pathogen evolves under the selective pressures of the host immune system and drug therapies. Furthermore, isolates with increased rates of mutation (hypermutator phenotype) emerged in the DK lineage. While this phenotype may accelerate evolution, we also show that hypermutators display differential mutagenesis of certain genes which enable them to follow alternative evolutionary pathways. Overall, our study identifies genes important for bacterial persistence and provides insight into the different mutational mechanisms that govern the adaptive genetic changes.
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Affiliation(s)
- Rasmus Lykke Marvig
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Helle Krogh Johansen
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
| | - Søren Molin
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
- * E-mail: (SM); (LJ)
| | - Lars Jelsbak
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
- * E-mail: (SM); (LJ)
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Hypermutable Pseudomonas aeruginosa in Cystic fibrosis patients from two Brazilian cities. J Clin Microbiol 2013; 51:927-30. [PMID: 23303495 DOI: 10.1128/jcm.02638-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hypermutable (HPM) strains of Pseudomonas aeruginosa have been found at high frequencies in cystic fibrosis (CF) patients in Europe. We report the results of testing for HPM frequencies, mutator genotype, and antimicrobial resistance of P. aeruginosa strains from Brazilian CF patients. A modified disk diffusion technique was used to quantify antibiotic-resistant subpopulations of an isolate, and estimations of the frequency of mutation to rifampin resistance were determined for 705 isolates from 149 patients attending clinics in two Brazilian cities. Mutations in the mutS gene were detected by sequencing assays. We found 194 (27.5%) HPM isolates in samples from 99 (66.4%) patients. Thirty-five HPM isolates (18.0%) from 31 (31.3%) patients exhibited a high increased spontaneous mutation rate compared with controls, and eight isolates from six patients displayed a defective mutS gene. The dominant HPM population was associated with very low antibiotic resistance levels, while HPM subpopulations were generally more resistant to antimicrobials. A relatively high prevalence of HPM P. aeruginosa in CF patients was associated with surprisingly low antibiotic resistance levels, in contrast to some earlier studies.
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Alcalá-Franco B, Montanari S, Cigana C, Bertoni G, Oliver A, Bragonzi A. Antibiotic pressure compensates the biological cost associated with Pseudomonas aeruginosa hypermutable phenotypes in vitro and in a murine model of chronic airways infection. J Antimicrob Chemother 2012; 67:962-9. [PMID: 22294647 DOI: 10.1093/jac/dkr587] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
OBJECTIVES Hypermutable strains of Pseudomonas aeruginosa frequently emerge during chronic airways infection in cystic fibrosis (CF) patients. While the increased accumulation of mutations by hypermutable strains determines a biological cost for the colonization of secondary environments, the mutator phenotypes might confer a selective advantage under antibiotic treatment in a CF airways environment. METHODS To test this hypothesis, the reference strain PAO1 and clonal pairs of CF clinical hypermutable and wild-type P. aeruginosa strains belonging to different genotypes were subjected to competition experiments in vitro and in a mouse model of chronic infection. RESULTS Both in vitro and in vivo, under antibiotic selection pressure, clinical hypermutable P. aeruginosa strains and the reference PAO1ΔmutS outcompeted their wild-type strains, promoting P. aeruginosa hypermutable strains in the airways colonization. This advantage for the hypermutable strain did not occur in the absence of antibiotic treatments. Severe histopathological lesions were detected during chronic murine airways infection after antibiotic pressure, indicating that the advantage of the hypermutable population in the lungs may contribute to disease progression. CONCLUSIONS Overall, these results showed that P. aeruginosa hypermutability, previously associated with a biological cost, increases colonization potential under selection pressure in a context of CF chronic airways infection and can contribute to lung damage during long-term persistence.
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Affiliation(s)
- Beatriz Alcalá-Franco
- Infections and Cystic Fibrosis Unit, Division of Immunology, Transplantation and Infectious Diseases, San Raffaele Scientific Institute, Milano, Italy
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Genotypic and phenotypic variation in Pseudomonas aeruginosa reveals signatures of secondary infection and mutator activity in certain cystic fibrosis patients with chronic lung infections. Infect Immun 2011; 79:4802-18. [PMID: 21930755 DOI: 10.1128/iai.05282-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Evolutionary adaptation of Pseudomonas aeruginosa to the cystic fibrosis lung is limited by genetic variation, which depends on rates of horizontal gene transfer and mutation supply. Because each may increase following secondary infection or mutator emergence, we sought to ascertain the incidence of secondary infection and genetic variability in populations containing or lacking mutators. Forty-nine strains collected over 3 years from 16 patients were phenotyped for antibiotic resistance and mutator status and were genotyped by repetitive-sequence PCR (rep-PCR), pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). Though phenotypic and genetic polymorphisms were widespread and clustered more strongly within than between longitudinal series, their distribution revealed instances of secondary infection. Sequence data, however, indicated that interlineage recombination predated initial strain isolation. Mutator series were more likely to be multiply antibiotic resistant, but not necessarily more variable in their nucleotide sequences, than nonmutators. One mutator and one nonmutator series were sequenced at mismatch repair loci and analyzed for gene content using DNA microarrays. Both were wild type with respect to mutL, but mutators carried an 8-bp mutS deletion causing a frameshift mutation. Both series lacked 126 genes encoding pilins, siderophores, and virulence factors whose inactivation has been linked to adaptation during chronic infection. Mutators exhibited loss of severalfold more genes having functions related to mobile elements, motility, and attachment. A 105-kb, 86-gene deletion was observed in one nonmutator that resulted in loss of virulence factors related to pyoverdine synthesis and elements of the multidrug efflux regulon. Diminished DNA repair activity may facilitate but not be absolutely required for rapid evolutionary change.
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Abstract
Pseudomonas aeruginosa is intrinsically resistant to a variety of antimicrobials and can develop resistance during anti-pseudomonal chemotherapy both of which compromise treatment of infections caused by this organism. Resistance to multiple classes of antimicrobials (multidrug resistance) in particular is increasingly common in P. aeruginosa, with a number of reports of pan-resistant isolates treatable with a single agent, colistin. Acquired resistance in this organism is multifactorial and attributable to chromosomal mutations and the acquisition of resistance genes via horizontal gene transfer. Mutational changes impacting resistance include upregulation of multidrug efflux systems to promote antimicrobial expulsion, derepression of ampC, AmpC alterations that expand the enzyme's substrate specificity (i.e., extended-spectrum AmpC), alterations to outer membrane permeability to limit antimicrobial entry and alterations to antimicrobial targets. Acquired mechanisms contributing to resistance in P. aeruginosa include β-lactamases, notably the extended-spectrum β-lactamases and the carbapenemases that hydrolyze most β-lactams, aminoglycoside-modifying enzymes, and 16S rRNA methylases that provide high-level pan-aminoglycoside resistance. The organism's propensity to grow in vivo as antimicrobial-tolerant biofilms and the occurrence of hypermutator strains that yield antimicrobial resistant mutants at higher frequency also compromise anti-pseudomonal chemotherapy. With limited therapeutic options and increasing resistance will the untreatable P. aeruginosa infection soon be upon us?
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Affiliation(s)
- Keith Poole
- Department of Microbiology and Immunology, Queen's University Kingston, ON, Canada
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Effect of ciprofloxacin concentration on the frequency and nature of resistant mutants selected from Pseudomonas aeruginosa mutS and mutT hypermutators. Antimicrob Agents Chemother 2011; 55:3668-76. [PMID: 21646492 DOI: 10.1128/aac.01826-10] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The rapid emergence of drug resistance upon treatment of Pseudomonas aeruginosa infections with fluoroquinolones is a serious concern. In this study, we report the effect of hypermutability on the mutant selection window for ciprofloxacin (CIP) by comparing the hypermutator MPAO1 mutS and mutT strains with the wild-type strain. The mutant selection window was shifted to higher CIP concentrations for both hypermutators, presenting the mutS strain with a broader selection window in comparison to the wild-type strain. The mutation prevention concentrations (MPC) determined for mutT and mutS strains were increased 2- and 4-fold over the wild-type level, respectively. In addition, we analyzed the molecular bases for resistance in the bacterial subpopulations selected at different points in the window. At the top of the window, the resistant clones isolated were mainly mutated in GyrA and ParC topoisomerase subunits, while at the bottom of the window, resistance was associated with the overexpression of MexCD-OprJ and MexAB-OprM efflux pumps. Accordingly, a greater proportion of multidrug-resistant clones were found among the subpopulations isolated at the lower CIP concentrations. Furthermore, we found that the exposure to CIP subinhibitory concentrations favors the accumulation of cells overexpressing MexCD-OprJ (due to mutations in the transcriptional repressor NfxB) and MexAB-OprM efflux pumps. We discuss these results in the context of the possible participation of this antibiotic in a mutagenic process.
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Poole K. Pseudomonas aeruginosa: resistance to the max. Front Microbiol 2011; 2:65. [PMID: 21747788 PMCID: PMC3128976 DOI: 10.3389/fmicb.2011.00065] [Citation(s) in RCA: 554] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 03/24/2011] [Indexed: 01/04/2023] Open
Abstract
Pseudomonas aeruginosa is intrinsically resistant to a variety of antimicrobials and can develop resistance during anti-pseudomonal chemotherapy both of which compromise treatment of infections caused by this organism. Resistance to multiple classes of antimicrobials (multidrug resistance) in particular is increasingly common in P. aeruginosa, with a number of reports of pan-resistant isolates treatable with a single agent, colistin. Acquired resistance in this organism is multifactorial and attributable to chromosomal mutations and the acquisition of resistance genes via horizontal gene transfer. Mutational changes impacting resistance include upregulation of multidrug efflux systems to promote antimicrobial expulsion, derepression of ampC, AmpC alterations that expand the enzyme's substrate specificity (i.e., extended-spectrum AmpC), alterations to outer membrane permeability to limit antimicrobial entry and alterations to antimicrobial targets. Acquired mechanisms contributing to resistance in P. aeruginosa include β-lactamases, notably the extended-spectrum β-lactamases and the carbapenemases that hydrolyze most β-lactams, aminoglycoside-modifying enzymes, and 16S rRNA methylases that provide high-level pan-aminoglycoside resistance. The organism's propensity to grow in vivo as antimicrobial-tolerant biofilms and the occurrence of hypermutator strains that yield antimicrobial resistant mutants at higher frequency also compromise anti-pseudomonal chemotherapy. With limited therapeutic options and increasing resistance will the untreatable P. aeruginosa infection soon be upon us?
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Affiliation(s)
- Keith Poole
- Department of Microbiology and Immunology, Queen's University Kingston, ON, Canada
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Oliver A, Mena A. Bacterial hypermutation in cystic fibrosis, not only for antibiotic resistance. Clin Microbiol Infect 2011; 16:798-808. [PMID: 20880409 DOI: 10.1111/j.1469-0691.2010.03250.x] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hypermutable or mutator microorganisms are those that have an increased spontaneous mutation rate as a result of defects in DNA repair or error avoidance systems. Over the last two decades, several studies have provided strong evidence for a relevant role of mutators in the evolution of natural bacterial populations, particularly in the field of infectious diseases. Among them, chronic respiratory infection with Pseudomonas aeruginosa in cystic fibrosis (CF) patients was the first natural environment to reveal the high prevalence and important role of mutators. A remarkable positive selection of mutators during the course of the chronic infection has been reported, mainly as a result of the emergence of DNA mismatch repair system (mutS, mutL or mutU)-deficient mutants, although strains defective in the GO system (mutM, mutY and mutT) have also been observed. High frequencies of mutators have also been noted among other pathogens in the CF setting, particularly Staphylococcus aureus and Haemophilus influenzae. Enhanced antimicrobial resistance development is the most thoroughly studied consequence of mutators in CF and other chronic infections, although recent studies show that mutators may additionally have important effects on the evolution of virulence, genetic adaptation to the airways of CF patients, persistence of colonization, transmissibility, and perhaps lung function decline. Further prospective clinical studies are nevertheless still needed for an in-depth evaluation of the impact of mutators on disease progression and outcome.
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Affiliation(s)
- A Oliver
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud, Palma de Mallorca, Spain.
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Hauser AR, Jain M, Bar-Meir M, McColley SA. Clinical significance of microbial infection and adaptation in cystic fibrosis. Clin Microbiol Rev 2011; 24:29-70. [PMID: 21233507 PMCID: PMC3021203 DOI: 10.1128/cmr.00036-10] [Citation(s) in RCA: 287] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A select group of microorganisms inhabit the airways of individuals with cystic fibrosis. Once established within the pulmonary environment in these patients, many of these microbes adapt by altering aspects of their structure and physiology. Some of these microbes and adaptations are associated with more rapid deterioration in lung function and overall clinical status, whereas others appear to have little effect. Here we review current evidence supporting or refuting a role for the different microbes and their adaptations in contributing to poor clinical outcomes in cystic fibrosis.
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Affiliation(s)
- Alan R Hauser
- Department of Microbiology/Immunology, Northwestern University, 303 E. Chicago Ave., Searle 6-495, Chicago, IL 60611, USA.
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Mucoidy, quorum sensing, mismatch repair and antibiotic resistance in Pseudomonas aeruginosa from cystic fibrosis chronic airways infections. PLoS One 2010; 5. [PMID: 20844762 PMCID: PMC2937033 DOI: 10.1371/journal.pone.0012669] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 08/18/2010] [Indexed: 01/19/2023] Open
Abstract
Survival of Pseudomonas aeruginosa in cystic fibrosis (CF) chronic infections is based on a genetic adaptation process consisting of mutations in specific genes, which can produce advantageous phenotypic switches and ensure its persistence in the lung. Among these, mutations inactivating the regulators MucA (alginate biosynthesis), LasR (quorum sensing) and MexZ (multidrug-efflux pump MexXY) are the most frequently observed, with those inactivating the DNA mismatch repair system (MRS) being also highly prevalent in P. aeruginosa CF isolates, leading to hypermutator phenotypes that could contribute to this adaptive mutagenesis by virtue of an increased mutation rate. Here, we characterized the mutations found in the mucA, lasR, mexZ and MRS genes in P. aeruginosa isolates obtained from Argentinean CF patients, and analyzed the potential association of mucA, lasR and mexZ mutagenesis with MRS-deficiency and antibiotic resistance. Thus, 38 isolates from 26 chronically infected CF patients were characterized for their phenotypic traits, PFGE genotypic patterns, mutations in the mucA, lasR, mexZ, mutS and mutL gene coding sequences and antibiotic resistance profiles. The most frequently mutated gene was mexZ (79%), followed by mucA (63%) and lasR (39%) as well as a high prevalence (42%) of hypermutators being observed due to loss-of-function mutations in mutL (60%) followed by mutS (40%). Interestingly, mutational spectra were particular to each gene, suggesting that several mechanisms are responsible for mutations during chronic infection. However, no link could be established between hypermutability and mutagenesis in mucA, lasR and mexZ, indicating that MRS-deficiency was not involved in the acquisition of these mutations. Finally, although inactivation of mucA, lasR and mexZ has been previously shown to confer resistance/tolerance to antibiotics, only mutations in MRS genes could be related to an antibiotic resistance increase. These results help to unravel the mutational dynamics that lead to the adaptation of P. aeruginosa to the CF lung.
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Riera E, Macià MD, Mena A, Mulet X, Pérez JL, Ge Y, Oliver A. Anti-biofilm and resistance suppression activities of CXA-101 against chronic respiratory infection phenotypes of Pseudomonas aeruginosa strain PAO1. J Antimicrob Chemother 2010; 65:1399-404. [PMID: 20435779 DOI: 10.1093/jac/dkq143] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVES Biofilm growth, mucoid phenotype and proficient resistance development by hypermutable strains dramatically limit the efficacy of current therapies for Pseudomonas aeruginosa chronic respiratory infection (CRI) in cystic fibrosis (CF) patients. We evaluated the activity of the new cephalosporin CXA-101, ceftazidime, meropenem and ciprofloxacin against biofilms of wild-type PAO1 and its mucoid (mucA), hypermutable (mutS) and mucoid-hypermutable derivatives, and analysed the capacity of these strains to develop resistance during planktonic and biofilm growth. METHODS MICs and MBCs were determined by microdilution, and mutant frequencies were determined at 4x and 16x the MICs. Biofilms were formed using a modified Calgary device and were incubated for 24 h with 0x, 1x, 4x or 16x the MIC of each antibiotic. Biofilms were plated, and total cells and resistant mutants enumerated. RESULTS CXA-101 showed concentration-independent biofilm bactericidal activity, being the most potent agent tested at 1x the MIC for wild-type, mucoid and hypermutable strains. The spontaneous mutant frequencies for CXA-101 were extremely low (<5 x 10(-11)), even for the hypermutable strain at low concentrations (4x the MIC), in sharp contrast to the other antipseudomonal agents. Accordingly, mutants resistant to 4x the MIC of CXA-101 did not emerge in biofilms for any of the strains/concentrations tested. CONCLUSION These data strongly suggest that resistance to CXA-101 (at least 4x the MIC) cannot be driven by single-step mutations, either in planktonic or in biofilm growth. CXA-101 shows encouraging properties for the treatment of CRI by P. aeruginosa, which need to be further evaluated in animal models and pertinent clinical trials.
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Affiliation(s)
- Elena Riera
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud (IUNICS), Palma de Mallorca, Spain
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Ciofu O, Mandsberg LF, Bjarnsholt T, Wassermann T, Høiby N. Genetic adaptation of Pseudomonas aeruginosa during chronic lung infection of patients with cystic fibrosis: strong and weak mutators with heterogeneous genetic backgrounds emerge in mucA and/or lasR mutants. Microbiology (Reading) 2010; 156:1108-1119. [DOI: 10.1099/mic.0.033993-0] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
During the chronic lung infection of patients with cystic fibrosis (CF), Pseudomonas aeruginosa can survive for long periods due to adaptive evolution mediated by genetic variation. Hypermutability is considered to play an important role in this adaptive evolution and it has been demonstrated that mutator populations are amplified in the CF lung by hitchhiking with adaptive mutations. Two of the genes that are frequently mutated in isolates from chronic infection are mucA and lasR. Loss-of-function mutations in these genes determine the phenotypic switch to mucoidy and loss of quorum sensing, which are considered hallmarks of chronic virulence. The aims of our study were to investigate (1) the genetic background of the P. aeruginosa subpopulations with non-mutator, weak or strong mutator phenotype and their dynamics during the chronic lung infection, and (2) the time sequence in which the hypermutable, mucoid and quorum-sensing-negative phenotypes emerge during chronic lung infection. For these purposes the sequences of mutS, mutL, uvrD, mutT, mutY and mutM anti-mutator genes as well as of mucA and lasR were analysed in 70 sequential P. aeruginosa isolates obtained from the respiratory secretions of 10 CF patients (one to three isolates per time point). Analysis of the genetic background of the mutator phenotype showed that mutS was the most commonly affected gene followed by mutL in isolates with strong mutator phenotype. The mutT, mutY, mutM genes were affected in isolates with low fold-changes in the mutation frequencies compared to the reference strain PAO1. Isolates with non-mutator, weak or strong mutator phenotype were represented at all time points showing co-existence of these subpopulations, which suggests parallel evolution of the various mutators in the different focal niches of infection in the CF lung. Mutations in mucA and lasR occurred earlier than mutations in the anti-mutator genes, showing that hypermutability is not a prerequisite for the acquisition of mucoidy and loss of quorum sensing, considered hallmarks of chronic virulence. Significantly higher mutation rates and MICs of ceftazidime, meropenem and ciprofloxacin were found for isolates collected late (more than 10 years) during the chronic lung infection compared to isolates collected earlier, which suggests an amplification of the mutator subpopulation by hitchhiking with development of antibiotic resistance. Similar evolutionary pathways concordant with adaptive radiation were observed in different clonal lineages of P. aeruginosa from CF patients.
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Affiliation(s)
- Oana Ciofu
- Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Denmark
| | - Lotte F. Mandsberg
- Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Denmark
| | - Thomas Bjarnsholt
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
- Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Denmark
| | - Tina Wassermann
- Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Denmark
| | - Niels Høiby
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
- Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Denmark
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Martha B, Croisier D, Fanton A, Astruc K, Piroth L, Huet F, Chavanet P. Factors associated with mucoid transition of Pseudomonas aeruginosa in cystic fibrosis patients. Clin Microbiol Infect 2009; 16:617-23. [PMID: 20002106 DOI: 10.1111/j.1469-0691.2009.02786.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Although the mucoid form of Pseudomonas aeruginosa (Pa) is largely responsible for the progression of lung disease in cystic fibrosis (CF), the relationship between factors relating daily-care regimes to mucoidy acquisition are as yet poorly investigated. Fifty-two CF patients registered at the CF centre of Dijon, France, were retrospectively evaluated from the date of Pa colonization either to the first positive sputum culture for mucoid Pa (n = 26) or to the last culture in which the Pa remained non-mucoid (n = 26). All clinical, pathological and therapeutic events were recorded. The association between the parameters collected and mucoid transition of Pa was assessed in a Cox model with time-dependant covariables. The mean follow-up was 4.7 + or - 4.3 years. Three independent parameters were associated with the higher risk of mucoid transition of Pa: persistence of Pa in sputum (OR 7.89; p <0.01), use of inhaled bronchodilators (OR 3.40; p = 0.04), and the use of inhaled colimycin (OR 4.04; p = 0.02). Isolation of Staphylococcus aureus, Haemophilus influenzae or Streptococcus pneumoniae in sputum was associated with a lower risk (OR 0.24; p < 0.01). Mucoid transition of Pa was associated with variables that reflected the severity of both lung disease and Pa colonization. Although they do not lead to prophylactic measures, these results corroborate the need to avoid Pa persistence.
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Affiliation(s)
- B Martha
- Service des Maladies Infectieuses, Centre Hospitalier Universitaire, Dijon, France.
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Ferroni A, Guillemot D, Moumile K, Bernede C, Le Bourgeois M, Waernessyckle S, Descamps P, Sermet-Gaudelus I, Lenoir G, Berche P, Taddei F. Effect of mutator P. aeruginosa on antibiotic resistance acquisition and respiratory function in cystic fibrosis. Pediatr Pulmonol 2009; 44:820-5. [PMID: 19598278 DOI: 10.1002/ppul.21076] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Cystic fibrosis patients suffer from recurrent bacterial infections that result in progressive deterioration of their respiratory function. Despite intensive antibiotic treatment, Pseudomonas aeruginosa is the main cause of such infections, with clones progressively developing multiple antibiotic resistance. We determined the relationship between the presence of P. aeruginosa mutator strains and cystic fibrosis clinical characteristics. METHODS We analyzed 136 strains of P. aeruginosa isolated from the expectorations of 36 CF patients. On all strains, mutation frequencies were determined by the mutation rate to rifampicin, and antibiotic susceptibility was determined by the disk diffusion method. The epidemiological relatedness of these 136 P. aeruginosa strains was studied by pulsed-field gel electrophoresis. The appearance of new antibiotic resistance by sequential analysis of genotypically identical strains was determined. Lung function test results, that is, forced expiratory volume in 1 sec and vital capacity, were also recorded from these patients. RESULTS We showed that bacteria with an enhanced mutation rate increase the rate of acquisition of new antibiotic resistance threefold and are associated with the deterioration of lung function. CONCLUSIONS This study demonstrates the effect of mutator bacteria on the efficiency of patient treatment and on their respiratory function. Given the consequence of antibiotic treatment failure and lung deterioration on the prognosis of CF patients, antibiotic treatment strategies may need to be optimized to prevent the emergence of mutator clones.
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Affiliation(s)
- Agnes Ferroni
- Laboratoire de Microbiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Necker-Enfants Malades, Paris, France.
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Pharmacodynamics of levofloxacin in a murine pneumonia model of Pseudomonas aeruginosa infection: determination of epithelial lining fluid targets. Antimicrob Agents Chemother 2009; 53:3325-30. [PMID: 19364849 DOI: 10.1128/aac.00006-09] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The dose choice for Pseudomonas aeruginosa remains a matter of debate. The actual exposure targets required for multilog killing of organisms at the primary infection site have not been delineated. We studied Pseudomonas aeruginosa PAO1 using a murine model of pneumonia. We employed a large mathematical model to fit all the concentration-time data in plasma and epithelial lining fluid (ELF) as well as colony counts in lung simultaneously for all drug doses. Penetration into ELF was calculated to be approximately 77.7%, as indexed to the ratio of the area under the concentration-time curve for ELF (AUC(ELF)) to the AUC(plasma). We determined the ELF concentration-time profile required to drive a stasis response as well as 1-, 2-, or 3-log(10)(CFU/g) kill. AUC/MIC ratios of 12.4, 31.2, 62.8, and 127.6 were required to drive these bacterial responses. Emergence of resistance was seen only at the two lowest doses (three of five animals at 50 mg/kg [body weight] and one of five animals at 100 mg/kg). The low exposure targets were likely driven by a low mutational frequency to resistance. Bridging to humans was performed using Monte Carlo simulation. With a 750-mg levofloxacin dose, target attainment rates fell below 90% at 4 mg/liter, 1 mg/liter, and 0.5 mg/liter for 1-, 2-, and 3-log kills, respectively. Given the low exposure targets seen with this strain, we conclude that levofloxacin at a 750-mg dose is not adequate for serious Pseudomonas aeruginosa pneumonia as a single agent. More isolates need to be studied to make these observations more robust.
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Mena A, Smith EE, Burns JL, Speert DP, Moskowitz SM, Perez JL, Oliver A. Genetic adaptation of Pseudomonas aeruginosa to the airways of cystic fibrosis patients is catalyzed by hypermutation. J Bacteriol 2008; 190:7910-7. [PMID: 18849421 PMCID: PMC2593214 DOI: 10.1128/jb.01147-08] [Citation(s) in RCA: 174] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 10/01/2008] [Indexed: 11/20/2022] Open
Abstract
In previous work (E. E. Smith, D. G. Buckley, Z. Wu, C. Saenphimmachack, L. R. Hoffman, D. A. D'Argenio, S. I. Miller, B. W. Ramsey, D. P. Speert, S. M. Moskowitz, J. L. Burns, R. Kaul, and M. V. Olson, Proc. Natl. Acad. Sci. USA 103:8487-8492, 2006) it was shown that Pseudomonas aeruginosa undergoes intense genetic adaptation during chronic respiratory infection (CRI) in cystic fibrosis (CF) patients. We used the same collection of isolates to explore the role of hypermutation in this process, since one of the hallmarks of CRI is the high prevalence of DNA mismatch repair (MMR) system-deficient mutator strains. The presence of mutations in 34 genes (many of them positively linked to adaptation in CF patients) in the study collection of 90 P. aeruginosa isolates obtained longitudinally from 29 CF patients was not homogeneous; on the contrary, mutations were significantly concentrated in the mutator lineages, which represented 17% of the isolates (87% MMR deficient). While sequential nonmutator lineages acquired a median of only 0.25 mutation per year of infection, mutator lineages accumulated more than 3 mutations per year. On the whole-genome scale, data for the first fully sequenced late CF isolate, which was also shown to be an MMR-deficient mutator, also support these findings. Moreover, for the first time the predicted amplification of mutator populations due to hitchhiking with adaptive mutations in the course of natural human infections is clearly documented. Interestingly, increased accumulation of mutations in mutator lineages was not a consequence of overrepresentation of mutations in genes involved in antimicrobial resistance, the only adaptive trait linked so far to hypermutation in CF patients, demonstrating that hypermutation also plays a major role in P. aeruginosa genome evolution and adaptation during CRI.
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Affiliation(s)
- A Mena
- Servicio de Microbiología, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud (IUNICS), Palma de Mallorca, Spain
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