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Baquero F, Martínez JL, Sánchez A, Fernández-de-Bobadilla MD, San-Millán A, Rodríguez-Beltrán J. Bacterial Subcellular Architecture, Structural Epistasis, and Antibiotic Resistance. BIOLOGY 2023; 12:biology12050640. [PMID: 37237454 DOI: 10.3390/biology12050640] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 04/08/2023] [Accepted: 04/20/2023] [Indexed: 05/28/2023]
Abstract
Epistasis refers to the way in which genetic interactions between some genetic loci affect phenotypes and fitness. In this study, we propose the concept of "structural epistasis" to emphasize the role of the variable physical interactions between molecules located in particular spaces inside the bacterial cell in the emergence of novel phenotypes. The architecture of the bacterial cell (typically Gram-negative), which consists of concentrical layers of membranes, particles, and molecules with differing configurations and densities (from the outer membrane to the nucleoid) determines and is in turn determined by the cell shape and size, depending on the growth phases, exposure to toxic conditions, stress responses, and the bacterial environment. Antibiotics change the bacterial cell's internal molecular topology, producing unexpected interactions among molecules. In contrast, changes in shape and size may alter antibiotic action. The mechanisms of antibiotic resistance (and their vectors, as mobile genetic elements) also influence molecular connectivity in the bacterial cell and can produce unexpected phenotypes, influencing the action of other antimicrobial agents.
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Affiliation(s)
- Fernando Baquero
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), 28034 Madrid, Spain
- CIBER en Epidemiología y Salud Pública (CIBERESP), 28034 Madrid, Spain
| | | | - Alvaro Sánchez
- Centro Nacional de Biotecnología, CSIC, 28049 Madrid, Spain
| | - Miguel D Fernández-de-Bobadilla
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), 28034 Madrid, Spain
- CIBER en Enfermedades Infecciosas (CIBERINFECT), 28034 Madrid, Spain
| | - Alvaro San-Millán
- Centro Nacional de Biotecnología, CSIC, 28049 Madrid, Spain
- CIBER en Enfermedades Infecciosas (CIBERINFECT), 28034 Madrid, Spain
| | - Jerónimo Rodríguez-Beltrán
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), 28034 Madrid, Spain
- CIBER en Enfermedades Infecciosas (CIBERINFECT), 28034 Madrid, Spain
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2
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Laborda P, Martínez JL, Hernando‐Amado S. Convergent phenotypic evolution towards fosfomycin collateral sensitivity of Pseudomonas aeruginosa antibiotic-resistant mutants. Microb Biotechnol 2022; 15:613-629. [PMID: 33960651 PMCID: PMC8867969 DOI: 10.1111/1751-7915.13817] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 04/06/2021] [Accepted: 04/07/2021] [Indexed: 12/19/2022] Open
Abstract
The rise of antibiotic resistance and the reduced amount of novel antibiotics support the need of developing novel strategies to fight infections, based on improving the use of the antibiotics we already have. Collateral sensitivity is an evolutionary trade-off associated with the acquisition of antibiotic resistance that can be exploited to tackle this relevant health problem. However, different works have shown that patterns of collateral sensitivity are not always conserved, thus precluding the exploitation of this evolutionary trade-off to fight infections. In this work, we identify a robust pattern of collateral sensitivity to fosfomycin in Pseudomonas aeruginosa antibiotic-resistant mutants, selected by antibiotics belonging to different structural families. We characterize the underlying mechanism of the collateral sensitivity observed, which is a reduced expression of the genes encoding the peptidoglycan-recycling pathway, which preserves the peptidoglycan synthesis in situations where its de novo synthesis is blocked, and a reduced expression of fosA, encoding a fosfomycin-inactivating enzyme. We propose that the identification of robust collateral sensitivity patterns, as well as the understanding of the molecular mechanisms behind these phenotypes, would provide valuable information to design evolution-based strategies to treat bacterial infections.
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Affiliation(s)
- Pablo Laborda
- Centro Nacional de BiotecnologíaCSICMadrid28049Spain
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3
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Baquero F, Martínez JL, F. Lanza V, Rodríguez-Beltrán J, Galán JC, San Millán A, Cantón R, Coque TM. Evolutionary Pathways and Trajectories in Antibiotic Resistance. Clin Microbiol Rev 2021; 34:e0005019. [PMID: 34190572 PMCID: PMC8404696 DOI: 10.1128/cmr.00050-19] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Evolution is the hallmark of life. Descriptions of the evolution of microorganisms have provided a wealth of information, but knowledge regarding "what happened" has precluded a deeper understanding of "how" evolution has proceeded, as in the case of antimicrobial resistance. The difficulty in answering the "how" question lies in the multihierarchical dimensions of evolutionary processes, nested in complex networks, encompassing all units of selection, from genes to communities and ecosystems. At the simplest ontological level (as resistance genes), evolution proceeds by random (mutation and drift) and directional (natural selection) processes; however, sequential pathways of adaptive variation can occasionally be observed, and under fixed circumstances (particular fitness landscapes), evolution is predictable. At the highest level (such as that of plasmids, clones, species, microbiotas), the systems' degrees of freedom increase dramatically, related to the variable dispersal, fragmentation, relatedness, or coalescence of bacterial populations, depending on heterogeneous and changing niches and selective gradients in complex environments. Evolutionary trajectories of antibiotic resistance find their way in these changing landscapes subjected to random variations, becoming highly entropic and therefore unpredictable. However, experimental, phylogenetic, and ecogenetic analyses reveal preferential frequented paths (highways) where antibiotic resistance flows and propagates, allowing some understanding of evolutionary dynamics, modeling and designing interventions. Studies on antibiotic resistance have an applied aspect in improving individual health, One Health, and Global Health, as well as an academic value for understanding evolution. Most importantly, they have a heuristic significance as a model to reduce the negative influence of anthropogenic effects on the environment.
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Affiliation(s)
- F. Baquero
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), Network Center for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - J. L. Martínez
- National Center for Biotechnology (CNB-CSIC), Madrid, Spain
| | - V. F. Lanza
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), Network Center for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain
- Central Bioinformatics Unit, Ramón y Cajal Institute for Health Research (IRYCIS), Madrid, Spain
| | - J. Rodríguez-Beltrán
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), Network Center for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - J. C. Galán
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), Network Center for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - A. San Millán
- National Center for Biotechnology (CNB-CSIC), Madrid, Spain
| | - R. Cantón
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), Network Center for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - T. M. Coque
- Department of Microbiology, Ramón y Cajal University Hospital, Ramón y Cajal Institute for Health Research (IRYCIS), Network Center for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain
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Sánchez-Romero MA, Casadesús J. Waddington's Landscapes in the Bacterial World. Front Microbiol 2021; 12:685080. [PMID: 34149674 PMCID: PMC8212987 DOI: 10.3389/fmicb.2021.685080] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 04/20/2021] [Indexed: 11/24/2022] Open
Abstract
Conrad Waddington’s epigenetic landscape, a visual metaphor for the development of multicellular organisms, is appropriate to depict the formation of phenotypic variants of bacterial cells. Examples of bacterial differentiation that result in morphological change have been known for decades. In addition, bacterial populations contain phenotypic cell variants that lack morphological change, and the advent of fluorescent protein technology and single-cell analysis has unveiled scores of examples. Cell-specific gene expression patterns can have a random origin or arise as a programmed event. When phenotypic cell-to-cell differences are heritable, bacterial lineages are formed. The mechanisms that transmit epigenetic states to daughter cells can have strikingly different levels of complexity, from the propagation of simple feedback loops to the formation of complex DNA methylation patterns. Game theory predicts that phenotypic heterogeneity can facilitate bacterial adaptation to hostile or unpredictable environments, serving either as a division of labor or as a bet hedging that anticipates future challenges. Experimental observation confirms the existence of both types of strategies in the bacterial world.
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Affiliation(s)
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
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Tarashi S, Badi SA, Moshiri A, Ebrahimzadeh N, Fateh A, Vaziri F, Aazami H, Siadat SD, Fuso A. The inter-talk between Mycobacterium tuberculosis and the epigenetic mechanisms. Epigenomics 2020; 12:455-469. [PMID: 32267165 DOI: 10.2217/epi-2019-0187] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Epigenetics regulate gene function without any alteration in the DNA sequence. The epigenetics represent one of the most important regulators in different cellular processes and have initially been developed in microorganisms as a protective strategy. The evaluation of the epigenetic mechanisms is also important in achieving an efficient control strategy in tuberculosis (TB). TB is one of the most significant epidemiological concerns in human history. Despite several in vivo and in vitro studies that have evaluated different epigenetic modifications in TB, many aspects of the association between epigenetics and TB are not fully understood. The current paper is aimed at reviewing our knowledge on histone modifications and DNA methylation modifications, as well as miRNAs regulation in TB.
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Affiliation(s)
- Samira Tarashi
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Mycobacteriology & Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | - Sara Ahmadi Badi
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Mycobacteriology & Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | - Arfa Moshiri
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Gastroenterology & Liver Diseases Research Center, Research Institute for Gastroenterology & Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Laboratory of Molecular Medicine, IRCCS Institute Giannina Gaslini, Genova, Italy
| | - Nayereh Ebrahimzadeh
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Mycobacteriology & Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | - Abolfazl Fateh
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Mycobacteriology & Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | - Farzam Vaziri
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Mycobacteriology & Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | - Hossein Aazami
- Endocrinology & Metabolism Research Center, Endocrinology & Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Seyed Davar Siadat
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Mycobacteriology & Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran.,Endocrinologyand Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Andrea Fuso
- Department of Experimental Medicine, Sapienza University of Rome, Italy
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Hernando-Amado S, Sanz-García F, Martínez JL. Antibiotic Resistance Evolution Is Contingent on the Quorum-Sensing Response in Pseudomonas aeruginosa. Mol Biol Evol 2020; 36:2238-2251. [PMID: 31228244 DOI: 10.1093/molbev/msz144] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Different works have explored independently the evolution toward antibiotic resistance and the role of eco-adaptive mutations in the adaptation to a new habitat (as the infected host) of bacterial pathogens. However, knowledge about the connection between both processes is still limited. We address this issue by comparing the evolutionary trajectories toward antibiotic resistance of a Pseudomonas aeruginosa lasR defective mutant and its parental wild-type strain, when growing in presence of two ribosome-targeting antibiotics. Quorum-sensing lasR defective mutants are selected in P. aeruginosa populations causing chronic infections. Further, we observed they are also selected in vitro as a first adaptation for growing in culture medium. By using experimental evolution and whole-genome sequencing, we found that the evolutionary trajectories of P. aeruginosa in presence of these antibiotics are different in lasR defective and in wild-type backgrounds, both at the phenotypic and the genotypic levels. Recreation of a set of mutants in both genomic backgrounds (either wild type or lasR defective) allowed us to determine the existence of negative epistatic interactions between lasR and antibiotic resistance determinants. These epistatic interactions could lead to mutual contingency in the evolution of antibiotic resistance when P. aeruginosa colonizes a new habitat in presence of antibiotics. If lasR mutants are selected first, this would constraint antibiotic resistance evolution. Conversely, when resistance mutations (at least those studied in the present work) are selected, lasR mutants may not be selected in presence of antibiotics. These results underlie the importance of contingency and epistatic interactions in modulating antibiotic resistance evolution.
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Scortti M, Han L, Alvarez S, Leclercq A, Moura A, Lecuit M, Vazquez-Boland J. Epistatic control of intrinsic resistance by virulence genes in Listeria. PLoS Genet 2018; 14:e1007525. [PMID: 30180166 PMCID: PMC6122793 DOI: 10.1371/journal.pgen.1007525] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 06/29/2018] [Indexed: 01/31/2023] Open
Abstract
Elucidating the relationships between antimicrobial resistance and virulence is key to understanding the evolution and population dynamics of resistant pathogens. Here, we show that the susceptibility of the gram-positive bacterium Listeria monocytogenes to the antibiotic fosfomycin is a complex trait involving interactions between resistance and virulence genes and the environment. We found that a FosX enzyme encoded in the listerial core genome confers intrinsic fosfomycin resistance to both pathogenic and non-pathogenic Listeria spp. However, in the genomic context of the pathogenic L. monocytogenes, FosX-mediated resistance is epistatically suppressed by two members of the PrfA virulence regulon, hpt and prfA, which upon activation by host signals induce increased fosfomycin influx into the bacterial cell. Consequently, in infection conditions, most L. monocytogenes isolates become susceptible to fosfomycin despite possessing a gene that confers high-level resistance to the drug. Our study establishes the molecular basis of an epistatic interaction between virulence and resistance genes controlling bacterial susceptibility to an antibiotic. The reported findings provide the rationale for the introduction of fosfomycin in the treatment of Listeria infections even though these bacteria are intrinsically resistant to the antibiotic in vitro.
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Affiliation(s)
- Mariela Scortti
- Microbial Pathogenesis Group, Division of Infection Medicine, Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, Little France campus, Edinburgh, United Kingdom
- Division of Infection & Immunity, The Roslin Institute, University of Edinburgh, Easter Bush campus, Edinburgh, United Kingdom
| | - Lei Han
- Microbial Pathogenesis Group, Division of Infection Medicine, Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, Little France campus, Edinburgh, United Kingdom
| | - Sonsiray Alvarez
- Microbial Pathogenesis Group, Division of Infection Medicine, Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, Little France campus, Edinburgh, United Kingdom
| | - Alexandre Leclercq
- Institut Pasteur, Biology of Infection Unit, INSERM U111 and National Reference Centre / WHO Collaborating Centre for Listeria, Paris, France
| | - Alexandra Moura
- Institut Pasteur, Biology of Infection Unit, INSERM U111 and National Reference Centre / WHO Collaborating Centre for Listeria, Paris, France
| | - Marc Lecuit
- Institut Pasteur, Biology of Infection Unit, INSERM U111 and National Reference Centre / WHO Collaborating Centre for Listeria, Paris, France
- Paris Descartes University, Division of Infectious Diseases and Tropical Medicine, Necker-Enfants Malades University Hospital, Paris, France
| | - Jose Vazquez-Boland
- Microbial Pathogenesis Group, Division of Infection Medicine, Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, Little France campus, Edinburgh, United Kingdom
- Division of Infection & Immunity, The Roslin Institute, University of Edinburgh, Easter Bush campus, Edinburgh, United Kingdom
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8
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de Oliveira MM, Dickman R. The advantage of being slow: The quasi-neutral contact process. PLoS One 2017; 12:e0182672. [PMID: 28806781 PMCID: PMC5555674 DOI: 10.1371/journal.pone.0182672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 07/22/2017] [Indexed: 01/09/2023] Open
Abstract
According to the competitive exclusion principle, in a finite ecosystem, extinction occurs naturally when two or more species compete for the same resources. An important question that arises is: when coexistence is not possible, which mechanisms confer an advantage to a given species against the other(s)? In general, it is expected that the species with the higher reproductive/death ratio will win the competition, but other mechanisms, such as asymmetry in interspecific competition or unequal diffusion rates, have been found to change this scenario dramatically. In this work, we examine competitive advantage in the context of quasi-neutral population models, including stochastic models with spatial structure as well as macroscopic (mean-field) descriptions. We employ a two-species contact process in which the “biological clock” of one species is a factor of αslower than that of the other species. Our results provide new insights into how stochasticity and competition interact to determine extinction in finite spatial systems. We find that a species with a slower biological clock has an advantage if resources are limited, winning the competition against a species with a faster clock, in relatively small systems. Periodic or stochastic environmental variations also favor the slower species, even in much larger systems.
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Affiliation(s)
- Marcelo Martins de Oliveira
- Departamento de Física e Matemática, Campus Alto Paraopeba, Universidade Federal de São João del Rei, Ouro Branco, Minas Gerais - Brazil
- * E-mail:
| | - Ronald Dickman
- Departamento de Física and National Institute of Science and Technology for Complex Systems, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais - Brazil
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Abrams AJ, Trees DL. Genomic sequencing of Neisseria gonorrhoeae to respond to the urgent threat of antimicrobial-resistant gonorrhea. Pathog Dis 2017; 75:3106325. [PMID: 28387837 PMCID: PMC6956991 DOI: 10.1093/femspd/ftx041] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 04/04/2017] [Indexed: 01/02/2023] Open
Abstract
The development of resistance of Neisseria gonorrhoeae to available first-line antibiotics, including penicillins, tetracyclines, fluoroquinolones and cephalosporins, has led to the circulation of multidrug-resistant gonorrhea at a global scale. Advancements in high-throughput whole-genome sequencing (WGS) provide useful tools that can be used to enhance gonococcal detection, treatment and management capabilities, which will ultimately aid in the control of antimicrobial resistant gonorrhea worldwide. In this minireview, we discuss the application of WGS of N. gonorrhoeae to strain typing, phylogenomic, molecular surveillance and transmission studies. We also examine the application of WGS analyses to the public health sector as well as the potential usage of WGS-based transcriptomic and epigenetic methods to identify novel gonococcal resistance mechanisms.
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Affiliation(s)
- A. Jeanine Abrams
- Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, US Department of Health and Human Services, Atlanta, GA 30333, USA
| | - David L. Trees
- Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, US Department of Health and Human Services, Atlanta, GA 30333, USA
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Disparities in capreomycin resistance levels associated with the rrs A1401G mutation in clinical isolates of Mycobacterium tuberculosis. Antimicrob Agents Chemother 2014; 59:444-9. [PMID: 25385119 DOI: 10.1128/aac.04438-14] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
As the prevalence of multidrug-resistant and extensively drug-resistant tuberculosis strains continues to rise, so does the need to develop accurate and rapid molecular tests to complement time-consuming growth-based drug susceptibility testing. Performance of molecular methods relies on the association of specific mutations with phenotypic drug resistance and while considerable progress has been made for resistance detection of first-line antituberculosis drugs, rapid detection of resistance for second-line drugs lags behind. The rrs A1401G allele is considered a strong predictor of cross-resistance between the three second-line injectable drugs, capreomycin (CAP), kanamycin, and amikacin. However, discordance is often observed between the rrs A1401G mutation and CAP resistance, with up to 40% of rrs A1401G mutants being classified as CAP susceptible. We measured the MICs to CAP in 53 clinical isolates harboring the rrs A1401G mutation and found that the CAP MICs ranged from 8 μg/ml to 40 μg/ml. These results were drastically different from engineered A1401G mutants generated in isogenic Mycobacterium tuberculosis, which exclusively exhibited high-level CAP MICs of 40 μg/ml. These data support the results of prior studies, which suggest that the critical concentration of CAP (10 μg/ml) used to determine resistance by indirect agar proportion may be too high to detect all CAP-resistant strains and suggest that a larger percentage of resistant isolates could be identified by lowering the critical concentration. These data also suggest that differences in resistance levels among clinical isolates are possibly due to second site or compensatory mutations located elsewhere in the genome.
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Contribution of phenotypic heterogeneity to adaptive antibiotic resistance. Proc Natl Acad Sci U S A 2013; 111:355-60. [PMID: 24351930 DOI: 10.1073/pnas.1316084111] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Antibiotic-resistant isolates of Salmonella enterica were selected on plates containing lethal concentrations of rifampicin, kanamycin, and nalidixic acid. The stability of the resistance phenotype was scored after nonselective growth. Rifampicin-resistant (Rif(r)) isolates were stable, suggesting that they had arisen by mutation. Mutations in the rpoB gene were detected indeed in Rif(r) mutants. In contrast, a fraction of kanamycin-resistant (Km(r)) and nalidixic acid-resistant (Nal(r)) isolates showed reduced resistance after nonselective growth, suggesting that mechanisms other than mutation had contributed to bacterial survival upon lethal selection. Single-cell analysis revealed heterogeneity in expression of the porin gene ompC, and subpopulation separation provided evidence that reduced ompC expression confers adaptive resistance to kanamycin. In the case of Nal(r) isolates, mutations in the gyrA gene were present in most nalidixic acid-resistant isolates. However, the efflux pump inhibitor Phe-Arg-β-naphtylamide (PAβN) reduced the level of resistance in Nal(r) mutants, indicating that active efflux contributes to the overall level of nalidixic acid resistance. Heterogeneous efflux pump activity was detected in single cells and colonies, and a correlation between high efflux and increased resistance to nalidixic acid was found. These observations suggest that fluctuations in the expression and the activity of critical functions of the bacterial cell, alone or combined with mutations, can contribute to adaptive resistance to antibiotics.
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