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Lazar V, Oprea E, Ditu LM. Resistance, Tolerance, Virulence and Bacterial Pathogen Fitness-Current State and Envisioned Solutions for the Near Future. Pathogens 2023; 12:pathogens12050746. [PMID: 37242416 DOI: 10.3390/pathogens12050746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 05/16/2023] [Accepted: 05/19/2023] [Indexed: 05/28/2023] Open
Abstract
The current antibiotic crisis and the global phenomena of bacterial resistance, inherited and non-inherited, and tolerance-associated with biofilm formation-are prompting dire predictions of a post-antibiotic era in the near future. These predictions refer to increases in morbidity and mortality rates as a consequence of infections with multidrug-resistant or pandrug-resistant microbial strains. In this context, we aimed to highlight the current status of the antibiotic resistance phenomenon and the significance of bacterial virulence properties/fitness for human health and to review the main strategies alternative or complementary to antibiotic therapy, some of them being already clinically applied or in clinical trials, others only foreseen and in the research phase.
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Affiliation(s)
- Veronica Lazar
- Department of Botany and Microbiology, Faculty of Biology, University of Bucharest, 1-3 Portocalelor Street, 060101 Bucharest, Romania
| | - Eliza Oprea
- Department of Botany and Microbiology, Faculty of Biology, University of Bucharest, 1-3 Portocalelor Street, 060101 Bucharest, Romania
| | - Lia-Mara Ditu
- Department of Botany and Microbiology, Faculty of Biology, University of Bucharest, 1-3 Portocalelor Street, 060101 Bucharest, Romania
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2
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Truşcă BS, Gheorghe-Barbu I, Manea M, Ianculescu E, Barbu IC, Măruțescu LG, Dițu LM, Chifiriuc MC, Lazăr V. Snapshot of Phenotypic and Molecular Virulence and Resistance Profiles in Multidrug-Resistant Strains Isolated in a Tertiary Hospital in Romania. Pathogens 2023; 12:pathogens12040609. [PMID: 37111495 PMCID: PMC10145626 DOI: 10.3390/pathogens12040609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/11/2023] [Accepted: 04/14/2023] [Indexed: 04/29/2023] Open
Abstract
A current major healthcare problem is represented by antibiotic resistance, mainly due to multidrug resistant (MDR) Gram negative bacilli (GNB), because of their extended spread both in hospital facilities and in the community's environment. The aim of this study was to investigate the virulence traits of Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa MDR, XDR, and PDR strains isolated from various hospitalized patients. These GNB strains were investigated for the presence of soluble virulence factors (VF), such as hemolysins, lecithinase, amylase, lipase, caseinase, gelatinase, and esculin hydrolysis, as well as for the presence of virulence genes encoding for VF involved in adherence (TC, fimH, and fimA), biofilm formation (algD, ecpRAB, mrkA, mrkD, ompA, and epsA), tissue destruction (plcH and plcN), and in toxin production (cnfI, hlyA, hlyD, and exo complex). All P. aeruginosa strains produced hemolysins; 90% produced lecithinase; and 80% harbored algD, plcH, and plcN genes. The esculin hydrolysis was detected in 96.1% of the K. pneumoniae strains, whereas 86% of them were positive for the mrkA gene. All of the A. baumannii strains produced lecithinase and 80% presented the ompA gene. A significant association was found between the number of VF and the XDR strains, regardless of the isolation sources. This study opens new research perspectives related to bacterial fitness and pathogenicity, and it provides new insights regarding the connection between biofilm formation, other virulence factors, and antibiotic resistance.
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Affiliation(s)
- Bianca Simona Truşcă
- Fundeni Clinical Institute, 022328 Bucharest, Romania
- Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania
| | - Irina Gheorghe-Barbu
- Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania
- Research Institute of the University of Bucharest-ICUB, 91-95 Spl. Independentei, 050567 Bucharest, Romania
| | - Marina Manea
- Fundeni Clinical Institute, 022328 Bucharest, Romania
- Fundeni Clinical Institute, University of Medicine and Pharmacy "Carol Davila" Bucharest, 020021 Bucharest, Romania
| | | | - Ilda Czobor Barbu
- Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania
- Research Institute of the University of Bucharest-ICUB, 91-95 Spl. Independentei, 050567 Bucharest, Romania
| | - Luminița Gabriela Măruțescu
- Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania
- Research Institute of the University of Bucharest-ICUB, 91-95 Spl. Independentei, 050567 Bucharest, Romania
| | - Lia-Mara Dițu
- Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania
- Research Institute of the University of Bucharest-ICUB, 91-95 Spl. Independentei, 050567 Bucharest, Romania
| | - Mariana-Carmen Chifiriuc
- Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania
- Research Institute of the University of Bucharest-ICUB, 91-95 Spl. Independentei, 050567 Bucharest, Romania
- Romanian Academy, 050045 Bucharest, Romania
| | - Veronica Lazăr
- Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, 060101 Bucharest, Romania
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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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4
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Role of Synonymous Mutations in the Evolution of TEM β-Lactamase Genes. Antimicrob Agents Chemother 2021; 65:AAC.00018-21. [PMID: 33820762 DOI: 10.1128/aac.00018-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/23/2021] [Indexed: 01/25/2023] Open
Abstract
Nonsynonymous mutations are well documented in TEM β-lactamases. The resulting amino acid changes often alter the conferred phenotype from broad spectrum (2b) conferred by TEM-1 to extended spectrum (2be), inhibitor resistant (2br), or both extended spectrum and inhibitor resistant (2ber). The encoding bla TEM genes also deviate in numerous synonymous mutations, which are not well understood. bla TEM-3 (2be), bla TEM-33 (2br), and bla TEM-109 (2ber) were studied in comparison to bla TEM-1 bla TEM-33 was chosen for more detailed studies because it deviates from bla TEM-1 by a single nonsynonymous mutation and three additional synonymous mutations. Genes encoding the enzymes with only nonsynonymous or all (including synonymous) mutations plus all permutations between bla TEM-1 and bla TEM-33 were expressed in Escherichia coli cells. In disc diffusion assays, genes encoding TEM-3, TEM-33, and TEM-109 with all synonymous mutations resulted in higher resistance levels than genes without synonymous mutations. Disc diffusion assays with the 16 genes carrying all possible nucleotide change combinations between bla TEM-1 and bla TEM-33 indicated different susceptibilities for different variants. Nucleotide BLAST searches did not identify genes without synonymous mutations but did identify some without nonsynonymous mutations. Energies of possible secondary mRNA structures calculated with mfold are generally higher with synonymous mutations, suggesting that their role could be to destabilize the mRNA and facilitate its unfolding for efficient translation. In summary, our data indicate that transition from bla TEM-1 to other variant genes by simply acquiring the nonsynonymous mutations is not favored. Instead, synonymous mutations seem to support the transition to other variant genes with nonsynonymous mutations leading to different phenotypes.
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5
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Yamazaki T, Matsuo J. Mutation frequency of Escherichia coli isolated from river water: potential role in the development of antimicrobial resistance. Can J Microbiol 2021; 67:651-656. [PMID: 33756093 DOI: 10.1139/cjm-2020-0547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bacteria acquire genetic variations that help them to adapt to stressful environmental conditions, and these changes may be associated with the development of antimicrobial resistance. In this study, we investigated the mutation frequencies of 270 isolates of Escherichia coli from river water, which represents a relatively unstressful environment. As we predicted, mutation frequencies of the E. coli isolates ranged from <1 × 10-11 to 6.3 × 10-8 (median, 1.7 × 10-9), and a strong mutator (≥ 4 × 10-7) was not detected. To better understand the role of mutation frequency in the development of antimicrobial resistance, we assessed antimicrobial sensitivity after exposure of the E. coli isolates to subinhibitory concentrations of ciprofloxacin, as a surrogate for stress. We found that antimicrobial resistance increased in bacteria with a low mutation frequency after exposure, and the relative increase in antimicrobial resistance generally increased, depending on the mutation frequency. Thus, mutation frequency may contribute to the development of antimicrobial resistance of bacteria in natural environments.
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Affiliation(s)
- Tomohiro Yamazaki
- School of Medical Technology, Health Sciences University of Hokkaido, Ainosato 2-5, Kita-ku, Sapporo 002-8072, Japan.,School of Medical Technology, Health Sciences University of Hokkaido, Ainosato 2-5, Kita-ku, Sapporo 002-8072, Japan
| | - Junji Matsuo
- School of Medical Technology, Health Sciences University of Hokkaido, Ainosato 2-5, Kita-ku, Sapporo 002-8072, Japan.,School of Medical Technology, Health Sciences University of Hokkaido, Ainosato 2-5, Kita-ku, Sapporo 002-8072, Japan
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6
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Campos M, San Millán Á, Sempere JM, Lanza VF, Coque TM, Llorens C, Baquero F. Simulating the Influence of Conjugative-Plasmid Kinetic Values on the Multilevel Dynamics of Antimicrobial Resistance in a Membrane Computing Model. Antimicrob Agents Chemother 2020; 64:e00593-20. [PMID: 32457104 PMCID: PMC7526830 DOI: 10.1128/aac.00593-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 05/15/2020] [Indexed: 12/17/2022] Open
Abstract
Bacterial plasmids harboring antibiotic resistance genes are critical in the spread of antibiotic resistance. It is known that plasmids differ in their kinetic values, i.e., conjugation rate, segregation rate by copy number incompatibility with related plasmids, and rate of stochastic loss during replication. They also differ in cost to the cell in terms of reducing fitness and in the frequency of compensatory mutations compensating plasmid cost. However, we do not know how variation in these values influences the success of a plasmid and its resistance genes in complex ecosystems, such as the microbiota. Genes are in plasmids, plasmids are in cells, and cells are in bacterial populations and microbiotas, which are inside hosts, and hosts are in human communities at the hospital or the community under various levels of cross-colonization and antibiotic exposure. Differences in plasmid kinetics might have consequences on the global spread of antibiotic resistance. New membrane computing methods help to predict these consequences. In our simulation, conjugation frequency of at least 10-3 influences the dominance of a strain with a resistance plasmid. Coexistence of different antibiotic resistances occurs if host strains can maintain two copies of similar plasmids. Plasmid loss rates of 10-4 or 10-5 or plasmid fitness costs of ≥0.06 favor plasmids located in the most abundant species. The beneficial effect of compensatory mutations for plasmid fitness cost is proportional to this cost at high mutation frequencies (10-3 to 10-5). The results of this computational model clearly show how changes in plasmid kinetics can modify the entire population ecology of antibiotic resistance in the hospital setting.
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Affiliation(s)
- Marcelino Campos
- Department of Microbiology, Ramón y Cajal University Hospital, IRYCIS, Madrid, Spain
- Valencian Research Institute for Artificial Intelligence (VRAIN), Universitat Politècnica de València, Valencia, Spain
| | - Álvaro San Millán
- Department of Microbiology, Ramón y Cajal University Hospital, IRYCIS, Madrid, Spain
- National Center for Biotechnology (CNB-CSIC), Madrid, Spain
- Network Research Center for Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - José M Sempere
- Valencian Research Institute for Artificial Intelligence (VRAIN), Universitat Politècnica de València, Valencia, Spain
| | - Val F Lanza
- Department of Microbiology, Ramón y Cajal University Hospital, IRYCIS, Madrid, Spain
- Bioinformatics Support Unit, IRYCIS, Madrid, Spain
- Network Research Center for Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - Teresa M Coque
- Department of Microbiology, Ramón y Cajal University Hospital, IRYCIS, Madrid, Spain
- Network Research Center for Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - Carlos Llorens
- Biotechvana, Valencia Technological Park, Paterna, Spain
| | - Fernando Baquero
- Department of Microbiology, Ramón y Cajal University Hospital, IRYCIS, Madrid, Spain
- Network Research Center for Epidemiology and Public Health (CIBERESP), Madrid, Spain
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7
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Thingholm KR, Hertz FB, Løbner-Olesen A, Frimodt-Møller N, Nielsen KL. Escherichia coli belonging to ST131 rarely transfers bla ctx-m-15 to fecal Escherichia coli. Infect Drug Resist 2019; 12:2429-2435. [PMID: 31496755 PMCID: PMC6689528 DOI: 10.2147/idr.s208536] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 05/23/2019] [Indexed: 01/22/2023] Open
Abstract
Background Extended spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) causing urinary tract infections often belong to sequence type 131 (ST131), serotype O25, carrying bla CTX-M-15. Aim The main aim of this study was to examine the conjugational frequencies of E. coli with plasmids carrying bla CTX-M-15 to E. coli isolates from the fecal flora of healthy humans to determine whether ST131 is more likely to uptake or donate ESBL resistance compared to other E. coli clones. Methods Donors and recipients were all clinical isolates and did not harbor plasmids with identical incompatibility groups (Inc-groups) based on in silico analyses of Inc-groups and restriction/modification systems (R/M-systems). The in vitro conjugation experiments were performed as filter conjugation with verification of transconjugants by random amplified polymorphic DNA (RAPD) PCR and bla CTX-M-15 PCR. Results The frequencies of conjugation with bla CTX-M-15-carrying plasmids were found to be very rare with detectable conjugation frequencies in the range of 4x10-9-7x10-7 transconjugants/recipient. Recipients of O25/ST131 type yielded significantly lower conjugation frequencies compared to recipients of other O-types (P=0.004). The applied ST131/O25 donors did not yield detectable levels of transconjugants regardless of the applied recipient. Presence of sub-MIC levels of ampicillin increased plasmid transfer frequencies x100 fold (P=0.07). Conclusion The results indicate that bla CTX-M-15 is rarely transferred by conjugation to E. coli isolates of the intestinal flora, even when the gene is plasmid-borne.
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Affiliation(s)
| | - Frederik Boëtius Hertz
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen 2100, Denmark.,Department of Clinical Microbiology, Herlev and Gentofte Hospital, Herlev 2730, Denmark
| | - Anders Løbner-Olesen
- Department of Biology, Section for Functional Genomics and Center for Bacterial Stress Response and Persistence, University of Copenhagen, Copenhagen, Denmark
| | | | - Karen Leth Nielsen
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen 2100, Denmark
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8
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Scanlan PD, Buckling A, Hall AR. Experimental evolution and bacterial resistance: (co)evolutionary costs and trade-offs as opportunities in phage therapy research. BACTERIOPHAGE 2015; 5:e1050153. [PMID: 26459626 DOI: 10.1080/21597081.2015.1050153] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 05/06/2015] [Accepted: 05/07/2015] [Indexed: 01/01/2023]
Abstract
Antagonistic coevolution between bacteria and phages (reciprocal selection for resistance and infectivity) has been demonstrated in a wide range of natural ecosystems, as well as experimental populations of microbes, yet exploiting knowledge of coevolution for the prophylactic and therapeutic use of phages is under-explored. In this addendum to our recent paper we discuss how real-time coevolution studies using experimental populations of bacteria and phages can provide novel insight into the changes in bacterial phenotypes that result from resistance evolution against coevolving phages, and how this may ultimately improve our understanding of phage therapy and ability to design effective treatments.
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Affiliation(s)
| | - Angus Buckling
- Biosciences; ESI; University of Exeter; Penryn Campus , Cornwall, UK
| | - Alex R Hall
- Institute of Integrative Biology ; ETH Zürich; Zürich, Switzerland
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9
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Tazzyman SJ, Hall AR. Lytic phages obscure the cost of antibiotic resistance in Escherichia coli. ISME JOURNAL 2015; 9:809-20. [PMID: 25268496 DOI: 10.1038/ismej.2014.176] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 08/21/2014] [Accepted: 08/25/2014] [Indexed: 01/07/2023]
Abstract
The long-term persistence of antibiotic-resistant bacteria depends on their fitness relative to other genotypes in the absence of drugs. Outside the laboratory, viruses that parasitize bacteria (phages) are ubiquitous, but costs of antibiotic resistance are typically studied in phage-free experimental conditions. We used a mathematical model and experiments with Escherichia coli to show that lytic phages strongly affect the incidence of antibiotic resistance in drug-free conditions. Under phage parasitism, the likelihood that antibiotic-resistant genetic backgrounds spread depends on their initial frequency, mutation rate and intrinsic growth rate relative to drug-susceptible genotypes, because these parameters determine relative rates of phage-resistance evolution on different genetic backgrounds. Moreover, the average cost of antibiotic resistance in terms of intrinsic growth in the antibiotic-free experimental environment was small relative to the benefits of an increased mutation rate in the presence of phages. This is consistent with our theoretical work indicating that, under phage selection, typical costs of antibiotic resistance can be outweighed by realistic increases in mutability if drug resistance and hypermutability are genetically linked, as is frequently observed in clinical isolates. This suggests the long-term distribution of antibiotic resistance depends on the relative rates at which different lineages adapt to other types of selection, which in the case of phage parasitism is probably extremely common, as well as costs of resistance inferred by classical in vitro methods.
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Affiliation(s)
| | - Alex R Hall
- Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland
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10
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Jolivet-Gougeon A, Bonnaure-Mallet M. Biofilms as a mechanism of bacterial resistance. DRUG DISCOVERY TODAY. TECHNOLOGIES 2015; 11:49-56. [PMID: 24847653 DOI: 10.1016/j.ddtec.2014.02.003] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Inside the biofilm, antimicrobial agents must overcome high cell density, an increased number of resistant mutants, substance delivery, molecular exchanges, such as high levels of beta-lactamases or inducers of efflux pump expression, and specific adaptive cells, so-called persisters. The environment within the biofilm modulates the response to antibiotics, especially when the SOS response or DNA repair systems are involved. Exposure to subinhibitory concentrations of antibiotics can enhance biofilm formation and mutagenesis. Thus, a global response to cell stress seems to be responsible for antibiotic-induced biofilm formation.
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11
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Rodríguez-Rojas A, Makarova O, Rolff J. Antimicrobials, stress and mutagenesis. PLoS Pathog 2014; 10:e1004445. [PMID: 25299705 PMCID: PMC4192597 DOI: 10.1371/journal.ppat.1004445] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 09/03/2014] [Indexed: 12/05/2022] Open
Abstract
Cationic antimicrobial peptides are ancient and ubiquitous immune effectors that multicellular organisms use to kill and police microbes whereas antibiotics are mostly employed by microorganisms. As antimicrobial peptides (AMPs) mostly target the cell wall, a microbial ‘Achilles heel’, it has been proposed that bacterial resistance evolution is very unlikely and hence AMPs are ancient ‘weapons’ of multicellular organisms. Here we provide a new hypothesis to explain the widespread distribution of AMPs amongst multicellular organism. Studying five antimicrobial peptides from vertebrates and insects, we show, using a classic Luria-Delbrück fluctuation assay, that cationic antimicrobial peptides (AMPs) do not increase bacterial mutation rates. Moreover, using rtPCR and disc diffusion assays we find that AMPs do not elicit SOS or rpoS bacterial stress pathways. This is in contrast to the main classes of antibiotics that elevate mutagenesis via eliciting the SOS and rpoS pathways. The notion of the ‘Achilles heel’ has been challenged by experimental selection for AMP-resistance, but our findings offer a new perspective on the evolutionary success of AMPs. Employing AMPs seems advantageous for multicellular organisms, as it does not fuel the adaptation of bacteria to their immune defenses. This has important consequences for our understanding of host-microbe interactions, the evolution of innate immune defenses, and also sheds new light on antimicrobial resistance evolution and the use of AMPs as drugs. Cationic antimicrobial peptides are ancient and ubiquitous immune effectors that multicellular organisms use to kill and police microbes, whilst antibiotics are mostly employed by microorganisms. Here we provide a new hypothesis to explain this widespread adoption of antimicrobial peptides. We show that cationic antimicrobial peptides (AMPs) do not increase bacterial mutagenesis, as they do not elicit bacterial stress pathways. Those stress pathways increase the mutation rate when bacteria are treated with antibiotics. Employing AMPs hence seems advantageous for multicellular organisms, as it does not fuel the adaptation of bacteria to their immune defenses. This has important consequences for our understanding of host-microbe interactions, the evolution of innate immune defenses, and also sheds new light on antimicrobial resistance evolution and the use of AMPs as drugs.
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Affiliation(s)
| | - Olga Makarova
- Evolutionary Biology, Institute for Biology, Free University Berlin, Berlin, Germany
| | - Jens Rolff
- Evolutionary Biology, Institute for Biology, Free University Berlin, Berlin, Germany
- * E-mail:
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12
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Bugs, hosts and ICU environment: countering pan-resistance in nosocomial microbiota and treating bacterial infections in the critical care setting. ACTA ACUST UNITED AC 2014; 61:e1-e19. [PMID: 24492197 DOI: 10.1016/j.redar.2013.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 11/04/2013] [Indexed: 02/07/2023]
Abstract
ICUs are areas where resistance problems are the largest, and these constitute a major problem for the intensivist's clinical practice. Main resistance phenotypes among nosocomial microbiota are (i) vancomycin-resistance/heteroresistance and tolerance in grampositives (MRSA, enterococci) and (ii) efflux pumps/enzymatic resistance mechanisms (ESBLs, AmpC, metallo-betalactamases) in gramnegatives. These phenotypes are found at different rates in pathogens causing respiratory (nosocomial pneumonia/ventilator-associated pneumonia), bloodstream (primary bacteremia/catheter-associated bacteremia), urinary, intraabdominal and surgical wound infections and endocarditis in the ICU. New antibiotics are available to overcome non-susceptibility in grampositives; however, accumulation of resistance traits in gramnegatives has led to multidrug resistance, a worrisome problem nowadays. This article reviews microorganism/infection risk factors for multidrug resistance, suggesting adequate empirical treatments. Drugs, patient and environmental factors all play a role in the decision to prescribe/recommend antibiotic regimens in the specific ICU patient, implying that intensivists should be familiar with available drugs, environmental epidemiology and patient factors.
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13
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Turrientes MC, Baquero F, Levin BR, Martínez JL, Ripoll A, González-Alba JM, Tobes R, Manrique M, Baquero MR, Rodríguez-Domínguez MJ, Cantón R, Galán JC. Normal mutation rate variants arise in a Mutator (Mut S) Escherichia coli population. PLoS One 2013; 8:e72963. [PMID: 24069167 PMCID: PMC3771984 DOI: 10.1371/journal.pone.0072963] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 07/22/2013] [Indexed: 01/08/2023] Open
Abstract
The rate at which mutations are generated is central to the pace of evolution. Although this rate is remarkably similar amongst all cellular organisms, bacterial strains with mutation rates 100 fold greater than the modal rates of their species are commonly isolated from natural sources and emerge in experimental populations. Theoretical studies postulate and empirical studies teort the hypotheses that these “mutator” strains evolved in response to selection for elevated rates of generation of inherited variation that enable bacteria to adapt to novel and/or rapidly changing environments. Less clear are the conditions under which selection will favor reductions in mutation rates. Declines in rates of mutation for established populations of mutator bacteria are not anticipated if such changes are attributed to the costs of augmented rates of generation of deleterious mutations. Here we report experimental evidence of evolution towards reduced mutation rates in a clinical isolate of Escherichia coli with an hyper-mutable phenotype due a deletion in a mismatch repair gene, (ΔmutS). The emergence in a ΔmutS background of variants with mutation rates approaching those of the normal rates of strains carrying wild-type MutS was associated with increase in fitness with respect to ancestral strain. We postulate that such an increase in fitness could be attributed to the emergence of mechanisms driving a permanent “aerobic style of life”, the negative consequence of this behavior being regulated by the evolution of mechanisms protecting the cell against increased endogenous oxidative radicals involved in DNA damage, and thus reducing mutation rate. Gene expression assays and full sequencing of evolved mutator and normo-mutable variants supports the hypothesis. In conclusion, we postulate that the observed reductions in mutation rate are coincidental to, rather than, the selective force responsible for this evolution.
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Affiliation(s)
- María-Carmen Turrientes
- Department of Microbiology, Ramón y Cajal Institute for Health Research, Madrid, Spain
- Centro de Investigación Biomedica en Red de Epidemiología y Salud Pública, Carlos III Health Institute, Madrid, Spain
| | - Fernando Baquero
- Department of Microbiology, Ramón y Cajal Institute for Health Research, Madrid, Spain
- Centro de Investigación Biomedica en Red de Epidemiología y Salud Pública, Carlos III Health Institute, Madrid, Spain
- Joint Unit for Research in Antibiotic Resistance and Virulence, Madrid, Spain
- * E-mail: (FB); (JCG)
| | - Bruce R. Levin
- Department of Biology, Emory University, Atlanta Georgia, United States of America
| | - José-Luis Martínez
- Joint Unit for Research in Antibiotic Resistance and Virulence, Madrid, Spain
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Madrid, Spain
| | - Aida Ripoll
- Department of Microbiology, Ramón y Cajal Institute for Health Research, Madrid, Spain
- Centro de Investigación Biomedica en Red de Epidemiología y Salud Pública, Carlos III Health Institute, Madrid, Spain
| | - José-María González-Alba
- Department of Microbiology, Ramón y Cajal Institute for Health Research, Madrid, Spain
- Centro de Investigación Biomedica en Red de Epidemiología y Salud Pública, Carlos III Health Institute, Madrid, Spain
| | - Raquel Tobes
- Research Department, Era7 Bioinformatics, Granada, Spain
| | | | | | | | - Rafael Cantón
- Department of Microbiology, Ramón y Cajal Institute for Health Research, Madrid, Spain
- Faculty of Health Sciences, Alfonso X El Sabio University, Madrid, Spain
| | - Juan-Carlos Galán
- Department of Microbiology, Ramón y Cajal Institute for Health Research, Madrid, Spain
- Centro de Investigación Biomedica en Red de Epidemiología y Salud Pública, Carlos III Health Institute, Madrid, Spain
- Joint Unit for Research in Antibiotic Resistance and Virulence, Madrid, Spain
- * E-mail: (FB); (JCG)
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14
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Kovacs B, Le Gall-David S, Vincent P, Le Bars H, Buffet-Bataillon S, Bonnaure-Mallet M, Jolivet-Gougeon A. Is biofilm formation related to the hypermutator phenotype in clinical Enterobacteriaceae isolates? FEMS Microbiol Lett 2013; 347:116-22. [PMID: 23909976 DOI: 10.1111/1574-6968.12229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 06/18/2013] [Accepted: 07/26/2013] [Indexed: 12/29/2022] Open
Abstract
In bacteria, complex adaptive processes are involved during transition from the planktonic to the biofilm mode of growth, and mutator strains are more prone to producing biofilms. Enterobacteriaceae species were isolated from urinary tract infections (UTIs; 222 strains) and from bloodstream infections (BSIs; 213 strains). Relationship between the hypermutable phenotype and biofilm forming capacity was investigated in these clinical strains. Mutation frequencies were estimated by monitoring the capacity of each strain to generate mutations that conferred rifampicin resistance on supplemented medium. Initiation of biofilm formation was assayed by determining the ability of the cells to adhere to a 96-well polystyrene microtitre plate. UTI Enterobacteriaceae strains showed significantly higher biofilm-forming capacity: 63.1% (54.0% for E. coli strains) vs. 42.3% for BSI strains (47.7% for E. coli). Strains isolated from UTIs did not present higher mutation frequencies than those from BSIs: contrary to what has been widely described for P. aeruginosa strains, isolated from pulmonary samples in patients suffering from cystic fibrosis, no relationship was found between the hypermutator phenotype in Enterobacteriaceae and the ability to initiate a biofilm.
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Affiliation(s)
- Bela Kovacs
- Department of Urology, Jahn Ferenc South-Pest Hospital, Budapest, Hungary
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15
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Baquero F, Tedim AP, Coque TM. Antibiotic resistance shaping multi-level population biology of bacteria. Front Microbiol 2013; 4:15. [PMID: 23508522 PMCID: PMC3589745 DOI: 10.3389/fmicb.2013.00015] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 01/22/2013] [Indexed: 12/21/2022] Open
Abstract
Antibiotics have natural functions, mostly involving cell-to-cell signaling networks. The anthropogenic production of antibiotics, and its release in the microbiosphere results in a disturbance of these networks, antibiotic resistance tending to preserve its integrity. The cost of such adaptation is the emergence and dissemination of antibiotic resistance genes, and of all genetic and cellular vehicles in which these genes are located. Selection of the combinations of the different evolutionary units (genes, integrons, transposons, plasmids, cells, communities and microbiomes, hosts) is highly asymmetrical. Each unit of selection is a self-interested entity, exploiting the higher hierarchical unit for its own benefit, but in doing so the higher hierarchical unit might acquire critical traits for its spread because of the exploitation of the lower hierarchical unit. This interactive trade-off shapes the population biology of antibiotic resistance, a composed-complex array of the independent "population biologies." Antibiotics modify the abundance and the interactive field of each of these units. Antibiotics increase the number and evolvability of "clinical" antibiotic resistance genes, but probably also many other genes with different primary functions but with a resistance phenotype present in the environmental resistome. Antibiotics influence the abundance, modularity, and spread of integrons, transposons, and plasmids, mostly acting on structures present before the antibiotic era. Antibiotics enrich particular bacterial lineages and clones and contribute to local clonalization processes. Antibiotics amplify particular genetic exchange communities sharing antibiotic resistance genes and platforms within microbiomes. In particular human or animal hosts, the microbiomic composition might facilitate the interactions between evolutionary units involved in antibiotic resistance. The understanding of antibiotic resistance implies expanding our knowledge on multi-level population biology of bacteria.
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Affiliation(s)
- Fernando Baquero
- Department of Microbiology, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación SanitariaMadrid, Spain
- Centros de Investigación Biomédica en Red de Epidemiología y Salud PúblicaMadrid, Spain
- Unidad de Resistencia a Antibióticos y Virulencia Bacteriana asociada al Consejo Superior de Investigaciones CientíficasMadrid, Spain
| | - Ana P. Tedim
- Department of Microbiology, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación SanitariaMadrid, Spain
- Centros de Investigación Biomédica en Red de Epidemiología y Salud PúblicaMadrid, Spain
| | - Teresa M. Coque
- Department of Microbiology, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación SanitariaMadrid, Spain
- Centros de Investigación Biomédica en Red de Epidemiología y Salud PúblicaMadrid, Spain
- Unidad de Resistencia a Antibióticos y Virulencia Bacteriana asociada al Consejo Superior de Investigaciones CientíficasMadrid, Spain
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16
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Toleman MA, Walsh TR. Combinatorial events of insertion sequences and ICE in Gram-negative bacteria. FEMS Microbiol Rev 2011; 35:912-35. [DOI: 10.1111/j.1574-6976.2011.00294.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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17
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Effect of higher minimum inhibitory concentrations of quaternary ammonium compounds in clinical E. coli isolates on antibiotic susceptibilities and clinical outcomes. J Hosp Infect 2011; 79:141-6. [PMID: 21807440 DOI: 10.1016/j.jhin.2011.06.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Accepted: 06/12/2011] [Indexed: 11/22/2022]
Abstract
Quaternary ammonium compounds (QACs) are cationic surfactants used as preservatives and environmental disinfectants. Limited data are available regarding the effect of QACs in the clinical setting. We performed a prospective cohort study in 153 patients with Escherichia coli bacteraemia from February to September 2008 at University Hospital in Rennes. The minimum inhibitory concentrations (MICs) of antibiotics and QACs alkyldimethylbenzylammonium chloride (ADBAC) and didecyldimethylammonium chloride (DDAC) were determined by the agar dilution method. The capacity of biofilm production was assayed using the Crystal Violet method, and mutation frequencies by measuring the capacity of strains to generate resistance to rifampicin. Logistic regression analysis showed that one of the significant factors related to low MICs for ADBAC (≤16 mg/L) and DDAC (≤8 mg/L), was cotrimoxazole susceptibility (odds ratio: 3.72; 95% confidence interval: 1.22-11.24; P=0.02 and OR: 3.61; 95% CI: 1.56-7.56; P<0.01, respectively). Antibiotic susceptibility to cotrimoxazole was strongly associated with susceptibility to amoxicillin and nalidixic acid (P<0.01). Community-acquired or healthcare-associated bacteraemia, severity of bacteraemia, and patient outcome were independent of the MICs of ADBAC and DDAC. Our findings demonstrate an epidemiological relationship between higher MIC values of QACs in clinical E. coli isolates and antibiotic resistance.
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18
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Jolivet-Gougeon A, Kovacs B, Le Gall-David S, Le Bars H, Bousarghin L, Bonnaure-Mallet M, Lobel B, Guillé F, Soussy CJ, Tenke P. Bacterial hypermutation: clinical implications. J Med Microbiol 2011; 60:563-573. [PMID: 21349992 DOI: 10.1099/jmm.0.024083-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Heritable hypermutation in bacteria is mainly due to alterations in the methyl-directed mismatch repair (MMR) system. MMR-deficient strains have been described from several bacterial species, and all of the strains exhibit increased mutation frequency and recombination, which are important mechanisms for acquired drug resistance in bacteria. Antibiotics select for drug-resistant strains and refine resistance determinants on plasmids, thus stimulating DNA recombination via the MMR system. Antibiotics can also act as indirect promoters of antibiotic resistance by inducing the SOS system and certain error-prone DNA polymerases. These alterations have clinical consequences in that efficacious treatment of bacterial infections requires high doses of antibiotics and/or a combination of different classes of antimicrobial agents. There are currently few new drugs with low endogenous resistance potential, and the development of such drugs merits further research.
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Affiliation(s)
- Anne Jolivet-Gougeon
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Bela Kovacs
- Department of Urology, Jahn Ferenc Del-Pesti Hospital, Koves ut 2, 1204 Budapest, Hungary
| | - Sandrine Le Gall-David
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Hervé Le Bars
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Latifa Bousarghin
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Martine Bonnaure-Mallet
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Bernard Lobel
- Service d'Urologie, CHU Pontchaillou, 2 rue Henri Le Guilloux, 35033 Rennes cedex 9, France
| | - François Guillé
- Service d'Urologie, CHU Pontchaillou, 2 rue Henri Le Guilloux, 35033 Rennes cedex 9, France
| | - Claude-James Soussy
- Service de Bactériologie-Virologie-Hygiène, CHU Henri-Mondor, 51 avenue du Maréchal-de-Lattre-de-Tassigny, 94010 Créteil cedex, France
| | - Peter Tenke
- Department of Urology, Jahn Ferenc Del-Pesti Hospital, Koves ut 2, 1204 Budapest, Hungary
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19
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Le Gall S, Desbordes L, Gracieux P, Saffroy S, Bousarghin L, Bonnaure-Mallet M, Jolivet-Gougeon A. Distribution of mutation frequencies among Salmonella enterica isolates from animal and human sources and genetic characterization of a Salmonella Heidelberg hypermutator. Vet Microbiol 2009; 137:306-12. [DOI: 10.1016/j.vetmic.2009.01.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 01/08/2009] [Accepted: 01/12/2009] [Indexed: 01/11/2023]
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20
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Abstract
The sustainability of life on the planet depends on the preservation of the existing microbial systems, which constitutes our major "biological atmosphere". The detection of variations in microbial systems as a result of anthropogenic or natural changes is critical both to detect and assess risks and to programme specific interventions. Changes in microbial systems provokes stress, probably altering the local evolutionary time by changing evolvability (the possibilities of microbes to evolve). Methods should be refined to properly assess diversity in microbial systems. We propose that such diversity estimations should be done on a multi-hierarchical scale, encompassing not only organisms, but sub-cellular entities (e.g. chromosomal domains, plasmids, transposons, integrons, genes, gene modules) and supra-cellular organizations (e.g. clones, populations, communities, ecosystems), applying Hamiltonian criteria of inclusive fitness for the different ensembles. In any of these entities, we can generally identify, in a fractal manner, constant and variable parts. Variation in these entities and ensembles is probably both reduced and increased by environmental stress. Because of that, variation in microbial systems might serve as mirrors or symptoms of the health of the planet.
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Affiliation(s)
- F Baquero
- Department of Microbiology-FIBio-RYC, CIBER-ESP and CSIC-Associated Unit on Bacterial Pathogenesis and Resistance, Ramón y Cajal University Hospital, Madrid, Spain.
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21
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Abstract
New concepts have emerged in the past few years that help us to better understand the emergence and spread of antimicrobial resistance (AMR). These include, among others, the discovery of the mutator state and the concept of mutant selection window for resistances emerging primarily through mutations in existing genes. Our understanding of horizontal gene transfer has also evolved significantly in the past few years, and important new mechanisms of AMR transfer have been discovered, including, among others, integrative conjugative elements and ISCR (insertion sequences with common regions) elements. Simultaneously, large-scale studies have helped us to start comprehending the immense and yet untapped reservoir of both AMR genes and mobile genetic elements present in the environment. Finally, new PCR- and DNA sequencing-based techniques are being developed that will allow us to better understand the epidemiology of classical vectors of AMR genes, such as plasmids, and to monitor them in a more global and systematic way.
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22
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Martinez JL, Fajardo A, Garmendia L, Hernandez A, Linares JF, Martínez-Solano L, Sánchez MB. A global view of antibiotic resistance. FEMS Microbiol Rev 2009; 33:44-65. [DOI: 10.1111/j.1574-6976.2008.00142.x] [Citation(s) in RCA: 236] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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23
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24
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Galán JC, Turrientes MC, Baquero MR, Rodríguez-Alcayna M, Martínez-Amado J, Martínez JL, Baquero F. Mutation rate is reduced by increased dosage of mutL gene in Escherichia coli K-12. FEMS Microbiol Lett 2007; 275:263-9. [PMID: 17825069 DOI: 10.1111/j.1574-6968.2007.00902.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
A variable but substantial proportion of wild Escherichia coli isolates present consistently lower mutation frequencies than that found in the ensemble of strains. The genetic mechanisms responsible for the hypo-mutation phenotype are much less known than those involved in hyper-mutation. Changes in E. coli mutation frequencies derived from the gene-copy effect of mutS, mutL, mutH, uvrD, mutT, mutY, mutM, mutA, dnaE, dnaQ, and rpoS are explored. When present in a very high copy number ( approximately 300 copies cell(-1)), mutL, mutH, and mutA gene copies yielded >/=twofold decrease in mutation rates determined by Luria-Delbrück fluctuation tests. Nevertheless, when the copy number was not such high ( approximately 15 copies cell(-1)), only mutL results in a consistent twofold decrease in the mutation rate. This reduction seems to be independent from the RecA background, phase of growth, or from the presence of proficient MutS. An increase in mutL gene copies was also able to partially compensate the hypermutator phenotype of a mutS-defective E. coli derivative.
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Affiliation(s)
- Juan-Carlos Galán
- Servicio de Microbiología, Hospital Universitario Ramón y Cajal (Unidad Asociada al CSIC Resistencia a Antibióticos y Virulencia Bacteriana) and CIBER-ESP, Madrid, Spain.
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25
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Hall LMC, Henderson-Begg SK. Hypermutable bacteria isolated from humans – a critical analysis. Microbiology (Reading) 2006; 152:2505-2514. [PMID: 16946246 DOI: 10.1099/mic.0.29079-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hypermutable bacteria of several species have been described among isolates recovered from humans over the last decade. Interpretation of the literature in this area is complicated by diversity in the determination and definition of hypermutability, and this review outlines the different methods used. Inactivation of the mismatch repair genemutSis often implicated in the mutator phenotype; the reported effect ofmutSinactivation on mutation frequency varies widely between species, from under 10-fold to nearly 1000-fold, but also varies among different reports on the same species. Particularly high proportions of mutators have been reported amongPseudomonas aeruginosaand other species in the cystic fibrosis lung, epidemic serogroup ANeisseria meningitidis, andHelicobacter pylori. Aspects of the biology of these infections that could be relevant to hypermutability are discussed, and some future directions that may increase our understanding of mutators among bacteria isolated from humans are considered.
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Affiliation(s)
- Lucinda M C Hall
- Centre for Infectious Disease, Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, 4 Newark Street, London E1 2AT, UK
| | - Stephanie K Henderson-Begg
- Centre for Infectious Disease, Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, 4 Newark Street, London E1 2AT, UK
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26
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Ellington MJ, Livermore DM, Pitt TL, Hall LMC, Woodford N. Development of extended-spectrum activity in TEM beta-lactamases in hyper-mutable, mutS Escherichia coli. Clin Microbiol Infect 2006; 12:800-3. [PMID: 16842578 DOI: 10.1111/j.1469-0691.2006.01424.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
TEM-1 and TEM(pUC19)beta-lactamases can gain activity against ceftazidime and other expanded-spectrum cephalosporins via point mutation. The frequency of emergent resistance to ceftazidime at 4 x MIC was elevated >or= 250-fold in hyper-mutable, MutS-deficient Escherichia coli harbouring these beta-lactamase genes on high- or low-copy plasmids. Moreover, although ceftazidime-resistant mutants, or those with reduced susceptibility, were selected in both the wild-type and mutS hosts, many more mutants in the mutS host showed ceftazidimase-type extended-spectrum beta-lactamase (ESBL) activity. This correlated with a G-A point mutation at position 484 in the bla(TEM-1) and bla(TEM-pUC19) genes, conferring the Arg164His amino-acid substitution found in the TEM-29 ESBL. Non-ESBL mutants lacked changes in bla(TEM).
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Affiliation(s)
- M J Ellington
- Antibiotic Resistance Monitoring and Reference Laboratory, Centre for Infections, Health Protection Agency, London, UK.
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27
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Abstract
Evolutionary success of bacteria relies on the constant fine-tuning of their mutation rates, which optimizes their adaptability to constantly changing environmental conditions. When adaptation is limited by the mutation supply rate, under some conditions, natural selection favours increased mutation rates by acting on allelic variation of the genetic systems that control fidelity of DNA replication and repair. Mutator alleles are carried to high frequency through hitchhiking with the adaptive mutations they generate. However, when fitness gain no longer counterbalances the fitness loss due to continuous generation of deleterious mutations, natural selection favours reduction of mutation rates. Selection and counter-selection of high mutation rates depends on many factors: the number of mutations required for adaptation, the strength of mutator alleles, bacterial population size, competition with other strains, migration, and spatial and temporal environmental heterogeneity. Such modulations of mutation rates may also play a role in the evolution of antibiotic resistance.
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Affiliation(s)
- Erick Denamur
- INSERM U722, Faculté de Médecine, Université Denis Diderot -- Paris 7, 16 rue Henri Huchard, 75018 Paris, France
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