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Paredes-Amaya CC, Ulloa MT, García-Angulo VA. Fierce poison to others: the phenomenon of bacterial dependence on antibiotics. J Biomed Sci 2023; 30:67. [PMID: 37574554 PMCID: PMC10424368 DOI: 10.1186/s12929-023-00963-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 08/07/2023] [Indexed: 08/15/2023] Open
Abstract
Beyond the development of resistance, the effects of antibiotics on bacteria and microbial communities are complex and far from exhaustively studied. In the context of the current global antimicrobial resistance crisis, understanding the adaptive and physiological responses of bacteria to antimicrobials is of paramount importance along with the development of new therapies. Bacterial dependence on antibiotics is a phenomenon in which antimicrobials instead of eliminating the pathogens actually provide a boost for their growth. This trait comprises an extreme example of the complexities of responses elicited by microorganisms to these drugs. This compelling evolutionary trait was readily described along with the first wave of antibiotics use and dependence to various antimicrobials has been reported. Nevertheless, current molecular characterizations have been focused on dependence on vancomycin, linezolid and colistin, three critically important antibiotics frequently used as last resource therapy for multi resistant pathogens. Outstanding advances have been made in understanding the molecular basis for the dependence to vancomycin, including specific mutations involved. Regarding linezolid and colistin, the general physiological components affected by the dependence, namely ribosomes and membrane function respectively, have been established. Nonetheless the implications of antibiotic dependence in clinically relevant features, such as virulence, epidemics, relationship with development of resistance, diagnostics and therapy effectiveness require clarification. This review presents a brief introduction of the phenomenon of bacterial dependence to antibiotics and a summary on early and current research concerning the basis for this trait. Furthermore, the available information on the effect of dependence in key clinical aspects is discussed. The studies performed so far underline the need to fully disclose the biological and clinical significance of this trait in pathogens to successfully assess its role in resistance and to design adjusted therapies.
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Affiliation(s)
- Claudia C Paredes-Amaya
- Microbiology Department, Escuela de Ciencias Básicas, Facultad de Salud, Universidad del Valle, Cali, Colombia
| | - María Teresa Ulloa
- Microbiology and Micology Program, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Independencia 1027, Independencia, RM, Santiago, Chile
- Vertebral I+D+i - Corporation for Assistance for Burned Children (Coaniquem), Santiago, Chile
| | - Víctor Antonio García-Angulo
- Microbiology and Micology Program, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Independencia 1027, Independencia, RM, Santiago, Chile.
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Nagy-Staron A, Tomasek K, Caruso Carter C, Sonnleitner E, Kavčič B, Paixão T, Guet CC. Local genetic context shapes the function of a gene regulatory network. eLife 2021; 10:e65993. [PMID: 33683203 PMCID: PMC7968929 DOI: 10.7554/elife.65993] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 02/19/2021] [Indexed: 11/13/2022] Open
Abstract
Gene expression levels are influenced by multiple coexisting molecular mechanisms. Some of these interactions such as those of transcription factors and promoters have been studied extensively. However, predicting phenotypes of gene regulatory networks (GRNs) remains a major challenge. Here, we use a well-defined synthetic GRN to study in Escherichia coli how network phenotypes depend on local genetic context, i.e. the genetic neighborhood of a transcription factor and its relative position. We show that one GRN with fixed topology can display not only quantitatively but also qualitatively different phenotypes, depending solely on the local genetic context of its components. Transcriptional read-through is the main molecular mechanism that places one transcriptional unit (TU) within two separate regulons without the need for complex regulatory sequences. We propose that relative order of individual TUs, with its potential for combinatorial complexity, plays an important role in shaping phenotypes of GRNs.
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Affiliation(s)
- Anna Nagy-Staron
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | - Kathrin Tomasek
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | | | - Elisabeth Sonnleitner
- Department of MicrobiologyImmunobiology and Genetics, Max F. Perutz Laboratories, Center Of Molecular Biology, University of ViennaViennaAustria
| | - Bor Kavčič
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | - Tiago Paixão
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | - Calin C Guet
- Institute of Science and Technology AustriaKlosterneuburgAustria
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García-Angulo VA, Herve B, Melo J, Sanhueza C, la Fuente SD, Aguirre LL, Baysdorfer C, Ulloa MT. Isolation and first draft genome sequence of a linezolid-dependent Staphylococcus aureus clinical strain. Future Microbiol 2020; 15:1123-1129. [PMID: 32954844 DOI: 10.2217/fmb-2020-0068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Background: Antibiotic-dependent pathogenic bacteria are sporadically isolated from patients that received prolonged antibiotic treatments. Evolution of antibiotics dependence and its clinical implications are scarcely studied. Materials & methods: A linezolid-dependent Staphylococcus aureus strain was isolated from a cystic fibrosis patient. A draft genome sequence was obtained and searched for known antibiotics resistance determinants and virulence factors. Results: The genome was assembled into 79 contigs for a total of 2.83 Mbp. This strain is a sequence type 5 methicillin-resistant Staphylococcus aureus with a type I SCCmec cassette also conserving the Panton-Valentine leukocidin. The G2576T substitution, conferring linezolid resistance, was harbored by all five copies of the 23S rRNA. Conclusion: The linezolid-dependent strain is related to a strain circulating in Latin America that acquired a mutation conferring linezolid resistance.
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Affiliation(s)
- Víctor A García-Angulo
- Microbiology & Mycology Program, Biomedical Sciences Institute, School of Medicine, University of Chile, Santiago 8380453, Chile
| | - Beatrice Herve
- Laboratorio Clínico, Clínica Las Condes, RM, Santiago 8340518, Chile
| | - Joel Melo
- Departamento de Medicina Interna, Clínica Las Condes, RM, Santiago 8340518, Chile
| | - Camila Sanhueza
- Microbiology & Mycology Program, Biomedical Sciences Institute, School of Medicine, University of Chile, Santiago 8380453, Chile
| | | | - Luis Lozano Aguirre
- Unidad de Análisis Bioinformáticos, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca 62209, México
| | - Chris Baysdorfer
- Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542, USA
| | - María Teresa Ulloa
- Microbiology & Mycology Program, Biomedical Sciences Institute, School of Medicine, University of Chile, Santiago 8380453, Chile
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Phenotypic Investigation of Vancomycin, Teicoplanin and Linezolid Resistance Among Enterococcus spp. Isolated from Children Diarrhea. JOURNAL OF PURE AND APPLIED MICROBIOLOGY 2019. [DOI: 10.22207/jpam.13.1.59] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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Hashimoto Y, Kurushima J, Nomura T, Tanimoto K, Tamai K, Yanagisawa H, Shirabe K, Ike Y, Tomita H. Dissemination and genetic analysis of the stealthy vanB gene clusters of Enterococcus faecium clinical isolates in Japan. BMC Microbiol 2018; 18:213. [PMID: 30545294 PMCID: PMC6293572 DOI: 10.1186/s12866-018-1342-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 11/14/2018] [Indexed: 12/18/2022] Open
Abstract
Background VanB-type vancomycin (VAN) resistance gene clusters confer VAN resistances on Enterococcus spp. over a wide range of MIC levels (MIC = 4–1000 mg/L). However, the epidemiology and the molecular characteristics of the VAN susceptible VanB-type Enterococcus still remain unclear. Results We characterized 19 isolates of VanB-type Enterococcus faecium that might colonize in the gut and were not phenotypically resistant to VAN (MIC = 3 mg/L). They were obtained from two hospitals in Japan between 2009 and 2010. These isolates had the identical vanB gene cluster and showed same multilocus sequence typing (MLST) (ST78) and the highly related profiles in pulsed-field gel electrophoresis (PFGE). The vanB gene cluster was located on a plasmid, and was transferable to E. faecium and E. faecalis. Notably, from these VanB-type VREs, VAN resistant (MIC≥16 mg/L) mutants could appear at a frequency of 10− 6–10− 7/parent cell in vitro. Most of these revertants acquired mutations in the vanSB gene, while the remainder of the revertants might have other mutations outside of the vanB gene cluster. All of the revertants we tested showed increases in the VAN-dependent expression of the vanB gene cluster, suggesting that the mutations affected the transcriptional activity and increased the VAN resistance. Targeted mutagenesis revealed that three unique nucleotide substitutions in the vanB gene cluster of these strains attenuated VAN resistance. Conclusions In summary, this study indicated that stealthy VanB-type E. faecium strains that have the potential ability to become resistance to VAN could exist in clinical settings. Electronic supplementary material The online version of this article (10.1186/s12866-018-1342-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yusuke Hashimoto
- Department of Bacteriology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan
| | - Jun Kurushima
- Department of Bacteriology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan
| | - Takahiro Nomura
- Department of Bacteriology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan
| | - Koichi Tanimoto
- Laboratory of Bacterial Drug Resistance, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan
| | - Kiyoko Tamai
- MIROKU Medical Laboratory Inc, 659-2 Innai, Saku, Nagano, 384-2201, Japan
| | - Hideji Yanagisawa
- MIROKU Medical Laboratory Inc, 659-2 Innai, Saku, Nagano, 384-2201, Japan
| | - Komei Shirabe
- Yamaguchi Prefectural Institute of Public Health and Environment, 2-5-67 Aoi, Yamaguchi, Yamaguchi, 753-0821, Japan
| | - Yasuyoshi Ike
- Department of Bacteriology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan
| | - Haruyoshi Tomita
- Department of Bacteriology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan. .,Laboratory of Bacterial Drug Resistance, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan.
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Whole genome characterization of a naturally occurring vancomycin-dependent Enterococcus faecium from a patient with bacteremia. INFECTION GENETICS AND EVOLUTION 2017; 52:96-99. [DOI: 10.1016/j.meegid.2017.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/03/2017] [Accepted: 05/04/2017] [Indexed: 11/15/2022]
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Miller WR, Munita JM, Arias CA. Mechanisms of antibiotic resistance in enterococci. Expert Rev Anti Infect Ther 2015; 12:1221-36. [PMID: 25199988 DOI: 10.1586/14787210.2014.956092] [Citation(s) in RCA: 370] [Impact Index Per Article: 41.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Multidrug-resistant (MDR) enterococci are important nosocomial pathogens and a growing clinical challenge. These organisms have developed resistance to virtually all antimicrobials currently used in clinical practice using a diverse number of genetic strategies. Due to this ability to recruit antibiotic resistance determinants, MDR enterococci display a wide repertoire of antibiotic resistance mechanisms including modification of drug targets, inactivation of therapeutic agents, overexpression of efflux pumps and a sophisticated cell envelope adaptive response that promotes survival in the human host and the nosocomial environment. MDR enterococci are well adapted to survive in the gastrointestinal tract and can become the dominant flora under antibiotic pressure, predisposing the severely ill and immunocompromised patient to invasive infections. A thorough understanding of the mechanisms underlying antibiotic resistance in enterococci is the first step for devising strategies to control the spread of these organisms and potentially establish novel therapeutic approaches.
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Affiliation(s)
- William R Miller
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical School, 6431 Fannin St. Rm. MSB 2.112, Houston, TX 77030, USA
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Hatcher J, Myers A, Donaldson H, Gordon AC, Meacher R, Baruah J. Comment on: Effects of selective digestive decontamination (SDD) on the gut resistome. J Antimicrob Chemother 2014; 69:3444-5. [DOI: 10.1093/jac/dku288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Santona A, Paglietti B, Al-Qahtani AA, Bohol MFF, Senok A, Deligios M, Rubino S, Al-Ahdal MN. Novel type of VanB2 teicoplanin-resistant hospital-associated Enterococcus faecium. Int J Antimicrob Agents 2014; 44:156-9. [DOI: 10.1016/j.ijantimicag.2014.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Accepted: 05/06/2014] [Indexed: 11/28/2022]
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Performance of the EUCAST disk diffusion method, the CLSI agar screen method, and the Vitek 2 automated antimicrobial susceptibility testing system for detection of clinical isolates of Enterococci with low- and medium-level VanB-type vancomycin resistance: a multicenter study. J Clin Microbiol 2014; 52:1582-9. [PMID: 24599985 DOI: 10.1128/jcm.03544-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Different antimicrobial susceptibility testing methods to detect low-level vancomycin resistance in enterococci were evaluated in a Scandinavian multicenter study (n=28). A phenotypically and genotypically well-characterized diverse collection of Enterococcus faecalis (n=12) and Enterococcus faecium (n=18) strains with and without nonsusceptibility to vancomycin was examined blindly in Danish (n=5), Norwegian (n=13), and Swedish (n=10) laboratories using the EUCAST disk diffusion method (n=28) and the CLSI agar screen (n=18) or the Vitek 2 system (bioMérieux) (n=5). The EUCAST disk diffusion method (very major error [VME] rate, 7.0%; sensitivity, 0.93; major error [ME] rate, 2.4%; specificity, 0.98) and CLSI agar screen (VME rate, 6.6%; sensitivity, 0.93; ME rate, 5.6%; specificity, 0.94) performed significantly better (P=0.02) than the Vitek 2 system (VME rate, 13%; sensitivity, 0.87; ME rate, 0%; specificity, 1). The performance of the EUCAST disk diffusion method was challenged by differences in vancomycin inhibition zone sizes as well as the experience of the personnel in interpreting fuzzy zone edges as an indication of vancomycin resistance. Laboratories using Oxoid agar (P<0.0001) or Merck Mueller-Hinton (MH) agar (P=0.027) for the disk diffusion assay performed significantly better than did laboratories using BBL MH II medium. Laboratories using Difco brain heart infusion (BHI) agar for the CLSI agar screen performed significantly better (P=0.017) than did those using Oxoid BHI agar. In conclusion, both the EUCAST disk diffusion and CLSI agar screening methods performed acceptably (sensitivity, 0.93; specificity, 0.94 to 0.98) in the detection of VanB-type vancomycin-resistant enterococci with low-level resistance. Importantly, use of the CLSI agar screen requires careful monitoring of the vancomycin concentration in the plates. Moreover, disk diffusion methodology requires that personnel be trained in interpreting zone edges.
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Chancey ST, Zähner D, Stephens DS. Acquired inducible antimicrobial resistance in Gram-positive bacteria. Future Microbiol 2013; 7:959-78. [PMID: 22913355 DOI: 10.2217/fmb.12.63] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
A major contributor to the emergence of antibiotic resistance in Gram-positive bacterial pathogens is the expansion of acquired, inducible genetic elements. Although acquired, inducible antibiotic resistance is not new, the interest in its molecular basis has been accelerated by the widening distribution and often 'silent' spread of the elements responsible, the diagnostic challenges of such resistance and the mounting limitations of available agents to treat Gram-positive infections. Acquired, inducible antibiotic resistance elements belong to the accessory genome of a species and are horizontally acquired by transformation/recombination or through the transfer of mobile DNA elements. The two key, but mechanistically very different, induction mechanisms are: ribosome-sensed induction, characteristic of the macrolide-lincosamide-streptogramin B antibiotics and tetracycline resistance, leading to ribosomal modifications or efflux pump activation; and resistance by cell surface-associated sensing of β-lactams (e.g., oxacillin), glycopeptides (e.g., vancomycin) and the polypeptide bacitracin, leading to drug inactivation or resistance due to cell wall alterations.
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Affiliation(s)
- Scott T Chancey
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
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Klare I, Fleige C, Geringer U, Witte W, Werner G. Performance of three chromogenic VRE screening agars, two Etest(®) vancomycin protocols, and different microdilution methods in detecting vanB genotype Enterococcus faecium with varying vancomycin MICs. Diagn Microbiol Infect Dis 2012; 74:171-6. [PMID: 22901792 DOI: 10.1016/j.diagmicrobio.2012.06.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 06/12/2012] [Accepted: 06/25/2012] [Indexed: 01/07/2023]
Abstract
Frequencies of vanB-type Enterococcus faecium increased in Europe during the last years. VanB enterococci show various levels of vancomycin MICs even below the susceptible breakpoint challenging a reliable diagnostics. The performance of 3 chromogenic vancomycin-resistant enterococci (VRE) screening agars, 2 Etest® vancomycin protocols, and different microdilution methods to detect 129 clinical vanB E. faecium strains was investigated. Altogether, 112 (87%) were correctly identified as VanB-type Enterococcus by microdilution MICs. An Etest® macromethod protocol was more sensitive than the standard protocol while keeping sufficient specificity in identifying 15 vanA/vanB-negative strains. Three chromogenic VRE agars performed similarly with 121 (94%), 123 (95%), and 124 (96%) vanB isolates that grew on Brilliance™ VRE Agar, CHROMagar™ VRE, and chromID™ VRE agar, respectively. Using identical media and conditions, we did not identify different growth behaviour on agar and in broth. A few vanB strains showed growth of microcolonies inside the Etest® vancomycin inhibition zones, suggesting a VanB heteroresistance phenotype.
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Affiliation(s)
- Ingo Klare
- National Reference Centre for Staphylococci and Enterococci, Division Nosocomial Infections, Department of Infectious Diseases, Robert Koch-Institut, Wernigerode Branch, Germany
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Bisicchia P, Bui NK, Aldridge C, Vollmer W, Devine KM. Acquisition of VanB-type vancomycin resistance by Bacillus subtilis: the impact on gene expression, cell wall composition and morphology. Mol Microbiol 2011; 81:157-78. [PMID: 21542863 DOI: 10.1111/j.1365-2958.2011.07684.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The vancomycin resistance operons from Enterococci, Staphylococci and Actinomycetes encode a VanRS two-component signal transduction system (TCS) and a suite of enzymes to modify the peptidoglycan biosynthetic precursor lipid II and to eliminate the D-Ala-D-Ala from the cell. Commingling of these regulatory and enzymatic activities with host functions has the potential to significantly impact host gene expression and cell wall metabolism. Here we report the effects of individually expressing the VanR(B) S(B) TCS and the VanY(B) WH(B) BX(B) resistance proteins in Bacillus subtilis. VanY(B) WH(B) BX(B) expression confers resistance to 2 µg ml(-1) of vancomycin with concomitant reduced Van-FL staining and leads to a cell division defect. In contrast to E. faecalis and S. aureus, VanS(B) is active in B. subtilis without vancomycin addition. Individual expression of the VanR(B) S(B) TCS and the VanY(B) WH(B) BX(B) resistance proteins repress and increase, respectively, expression of PhoPR regulon genes in the phosphate-limited state. When vancomycin-resistant cells are exposed to elevated vancomycin levels, mutant strains with increased resistance to vancomycin and a growth dependency on vanY(B) WH(B) BX(B) expression frequently arise. Mutation of the endogenous Ddl ligase is the necessary and sufficient cause of both phenotypes. We discuss how these effects may influence establishment of van operons in new host bacteria.
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Affiliation(s)
- Paola Bisicchia
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
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Choi HJ, Nam D, Peck KR, Song JH, Shin D, Ko KS. Loss of vancomycin resistance not completely dependent on the Tn1546 element in Enterococcus faecium isolates. Diagn Microbiol Infect Dis 2011; 69:105-10. [PMID: 21146722 DOI: 10.1016/j.diagmicrobio.2010.08.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 08/06/2010] [Accepted: 08/21/2010] [Indexed: 11/27/2022]
Abstract
We investigated characteristics of 3 Enterococcus faecium strains (SHY-1, SHY-2, and SHY-3) isolated successively from 1 patient. In vitro susceptibility testing was performed using broth microdilution method. Change of vancomycin MIC was monitored during incubation with vancomycin for SHY-3 strain. Genetic backgrounds were determined both by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). In addition, the genetic variations among Tn1546 element were investigated by polymerase chain reaction (PCR) assay and sequencing. vanA and vanX expression of 3 strains was evaluated using quantitative real-time (qRT)-PCR method. Although all the strains possessed the vanA gene, SHY-3 was susceptible to glycopeptides, while SHY-1 and SHY-2 were resistant to glycopeptides. Judged by MLST and PFGE, 3 strains have the same genetic background. The vancomycin resistance of SHY-3 was not recovered after exposure to vancomycin. The vanA and vanX genes were expressed in strains SHY-1 and SHY-2 but not in strain SHY-3, although the SHY-2 and SHY-3 strains shared the same arrangement of the van gene cluster, a common 88-bp deletion in vanS gene. Our results indicate that vancomycin resistance might not be completely dependent on the Tn1546 element.
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Affiliation(s)
- Hyun Jin Choi
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, South Korea
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Compensation of fitness costs and reversibility of antibiotic resistance mutations. Antimicrob Agents Chemother 2010; 54:2085-95. [PMID: 20176903 DOI: 10.1128/aac.01460-09] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Strains of bacterial pathogens that have acquired mutations conferring antibiotic resistance often have a lower growth rate and are less invasive or transmissible initially than their susceptible counterparts. However, fitness costs of resistance mutations can be ameliorated by secondary site mutations. These so-called compensatory mutations may restore fitness in the absence and/or presence of antimicrobials. We review literature data and show that the fitness gains in the absence and presence of antibiotic treatment need not be correlated. The aim of this study is to gain a better conceptual grasp of how compensatory mutations with different fitness gains affect evolutionary trajectories, in particular reversibility. To this end, we developed a theoretical model with which we consider both a resistance and a compensation locus. We propose an intuitively understandable parameterization for the fitness values of the four resulting genotypes (wild type, resistance mutation only, compensatory mutation only, and both mutations) in the absence and presence of treatment. The differential fitness gains, together with the turnover rate and the mutation rate, strongly affected the success of antibacterial treatment, reversibility, and long-term abundance of resistant strains. We therefore propose that experimental studies of compensatory mutations should include fitness measurements of all possible genotypes in both the absence and presence of an antibiotic.
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