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Galarion LH, Trigwell J, Mohamad M, Nakamoto JA, Clarke JE, Atkinson GC, O’Neill AJ. The native ABC-F proteins of Staphylococcus aureus do not contribute to intrinsic resistance against ribosome-targeting antibacterial drugs. J Antimicrob Chemother 2023; 78:2601-2603. [PMID: 37585343 PMCID: PMC10810581 DOI: 10.1093/jac/dkad238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2023] Open
Affiliation(s)
- Luiza H Galarion
- Faculty of Biological Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - James Trigwell
- Faculty of Biological Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Merianne Mohamad
- Faculty of Biological Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Jose A Nakamoto
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Justin E Clarke
- Faculty of Biological Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Gemma C Atkinson
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Alex J O’Neill
- Faculty of Biological Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
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Galarion LH, Mitchell JK, Randall CP, O’Neill AJ. An extensively validated whole-cell biosensor for specific, sensitive and high-throughput detection of antibacterial inhibitors targeting cell-wall biosynthesis. J Antimicrob Chemother 2023; 78:646-655. [PMID: 36626387 PMCID: PMC9978594 DOI: 10.1093/jac/dkac429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 12/02/2022] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Whole-cell biosensor strains are powerful tools for antibacterial drug discovery, in principle allowing the identification of inhibitors acting on specific, high-value target pathways. Whilst a variety of biosensors have been described for detecting cell-wall biosynthesis inhibitors (CWBIs), these strains typically lack specificity and/or sensitivity, and have for the most part not been rigorously evaluated as primary screening tools. Here, we describe several Staphylococcus aureus CWBI biosensors and show that specific and sensitive biosensor-based discovery of CWBIs is achievable. METHODS Biosensors comprised lacZ reporter fusions with S. aureus promoters (PgltB, PilvD, PmurZ, PoppB, PORF2768, PsgtB) that are subject to up-regulation following inhibition of cell-wall biosynthesis. Induction of biosensors was detected by measuring expression of β-galactosidase using fluorogenic or luminogenic substrates. RESULTS Three of the six biosensors tested (those based on PgltB, PmurZ, PsgtB) exhibited apparently specific induction of β-galactosidase expression in the presence of CWBIs. Further validation of one of these (PmurZ) using an extensive array of positive and negative control compounds and conditional mutants established that it responded appropriately and uniquely to inhibition of cell-wall biosynthesis. Using this biosensor, we established, validated and deployed a high-throughput assay that identified a potentially novel CWBI from a screen of >9000 natural product extracts. CONCLUSIONS Our extensively validated PmurZ biosensor strain offers specific and sensitive detection of CWBIs, and is well-suited for high-throughput screening; it therefore represents a valuable tool for antibacterial drug discovery.
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Affiliation(s)
- Luiza H Galarion
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Jennifer K Mitchell
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Christopher P Randall
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
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Abstract
Members of the ATP-binding cassette (ABC)-F protein subfamily collectively mediate resistance to a broader range of clinically important antibiotic classes than any other group of resistance proteins and are widespread in pathogenic bacteria. Following over 25 years' of controversy regarding the mechanism by which these proteins work, it has recently been established that they provide antibiotic resistance through the previously recognized but underappreciated phenomenon of target protection; they bind to the ribosome to effect the release of ribosome-targeted antibiotics, thereby rescuing the translation apparatus from antibiotic-mediated inhibition. Here we review the ABC-F resistance proteins with an emphasis on their mechanism of action, first exploring the history of the debate about how these proteins work and outlining our current state of knowledge and then considering key questions to be addressed in understanding the molecular detail of their function.
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Affiliation(s)
- Liam K. R. Sharkey
- Antimicrobial Research Centre and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Alex J. O’Neill
- Antimicrobial Research Centre and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
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Charlton MH, Aleksis R, Saint-Leger A, Gupta A, Loza E, Ribas de Pouplana L, Kaula I, Gustina D, Madre M, Lola D, Jaudzems K, Edmund G, Randall CP, Kime L, O’Neill AJ, Goessens W, Jirgensons A, Finn PW. N-Leucinyl Benzenesulfonamides as Structurally Simplified Leucyl-tRNA Synthetase Inhibitors. ACS Med Chem Lett 2018; 9:84-88. [PMID: 29456792 DOI: 10.1021/acsmedchemlett.7b00374] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 01/18/2018] [Indexed: 12/12/2022] Open
Abstract
N-Leucinyl benzenesulfonamides have been discovered as a novel class of potent inhibitors of E. coli leucyl-tRNA synthetase. The binding of inhibitors to the enzyme was measured by using isothermal titration calorimetry. This provided information on enthalpy and entropy contributions to binding, which, together with docking studies, were used for structure-activity relationship analysis. Enzymatic assays revealed that N-leucinyl benzenesulfonamides display remarkable selectivity for E. coli leucyl-tRNA synthetase compared to S. aureus and human orthologues. The simplest analogue of the series, N-leucinyl benzenesulfonamide (R = H), showed the highest affinity against E. coli leucyl-tRNA synthetase and also exhibited antibacterial activity against Gram-negative pathogens (the best MIC = 8 μg/mL, E. coli ATCC 25922), which renders it as a promising template for antibacterial drug discovery.
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Affiliation(s)
- Michael H. Charlton
- Oxford Drug Design Ltd., Oxford Centre for Innovation, New Road, Oxford, OX1 1BY. U.K
| | - Rihards Aleksis
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Adélaïde Saint-Leger
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Catalonia, Spain
- ICREA, Pg. Lluís Company 23, 08010 Barcelona, Catalonia, Spain
| | - Arya Gupta
- Antimicrobial
Research Centre and School of Molecular and Cellular Biology, Faculty
of Biological Sciences, University of Leeds, Leeds, LS2 9JT, U.K
| | - Einars Loza
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Lluís Ribas de Pouplana
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10, 08028 Barcelona, Catalonia, Spain
- ICREA, Pg. Lluís Company 23, 08010 Barcelona, Catalonia, Spain
| | - Ilze Kaula
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Daina Gustina
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Marina Madre
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Daina Lola
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Kristaps Jaudzems
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Grace Edmund
- Oxford Drug Design Ltd., Oxford Centre for Innovation, New Road, Oxford, OX1 1BY. U.K
| | - Christopher P. Randall
- Antimicrobial
Research Centre and School of Molecular and Cellular Biology, Faculty
of Biological Sciences, University of Leeds, Leeds, LS2 9JT, U.K
| | - Louise Kime
- Antimicrobial
Research Centre and School of Molecular and Cellular Biology, Faculty
of Biological Sciences, University of Leeds, Leeds, LS2 9JT, U.K
| | - Alex J. O’Neill
- Antimicrobial
Research Centre and School of Molecular and Cellular Biology, Faculty
of Biological Sciences, University of Leeds, Leeds, LS2 9JT, U.K
| | - Wil Goessens
- Erasmus University Medical Center Rotterdam, Department
of Medical Microbiology and Infectious Diseases, Wytemaweg 80, 3015 CN, Rotterdam, The Netherlands
| | - Aigars Jirgensons
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga LV-1006, Latvia
| | - Paul W. Finn
- Oxford Drug Design Ltd., Oxford Centre for Innovation, New Road, Oxford, OX1 1BY. U.K
- Department
of Applied Computing, University of Buckingham, Hunter Street, Buckingham, MK18 1EG, U.K
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Elkrewi E, Randall CP, Ooi N, Cottell JL, O’Neill AJ. Cryptic silver resistance is prevalent and readily activated in certain Gram-negative pathogens. J Antimicrob Chemother 2017; 72:3043-3046. [DOI: 10.1093/jac/dkx258] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 06/30/2017] [Indexed: 11/13/2022] Open
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Gerits E, Blommaert E, Lippell A, O’Neill AJ, Weytjens B, De Maeyer D, Fierro AC, Marchal K, Marchand A, Chaltin P, Spincemaille P, De Brucker K, Thevissen K, Cammue BPA, Swings T, Liebens V, Fauvart M, Verstraeten N, Michiels J. Elucidation of the Mode of Action of a New Antibacterial Compound Active against Staphylococcus aureus and Pseudomonas aeruginosa. PLoS One 2016; 11:e0155139. [PMID: 27167126 PMCID: PMC4864301 DOI: 10.1371/journal.pone.0155139] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 04/25/2016] [Indexed: 01/29/2023] Open
Abstract
Nosocomial and community-acquired infections caused by multidrug resistant bacteria represent a major human health problem. Thus, there is an urgent need for the development of antibiotics with new modes of action. In this study, we investigated the antibacterial characteristics and mode of action of a new antimicrobial compound, SPI031 (N-alkylated 3, 6-dihalogenocarbazol 1-(sec-butylamino)-3-(3,6-dichloro-9H-carbazol-9-yl)propan-2-ol), which was previously identified in our group. This compound exhibits broad-spectrum antibacterial activity, including activity against the human pathogens Staphylococcus aureus and Pseudomonas aeruginosa. We found that SPI031 has rapid bactericidal activity (7-log reduction within 30 min at 4x MIC) and that the frequency of resistance development against SPI031 is low. To elucidate the mode of action of SPI031, we performed a macromolecular synthesis assay, which showed that SPI031 causes non-specific inhibition of macromolecular biosynthesis pathways. Liposome leakage and membrane permeability studies revealed that SPI031 rapidly exerts membrane damage, which is likely the primary cause of its antibacterial activity. These findings were supported by a mutational analysis of SPI031-resistant mutants, a transcriptome analysis and the identification of transposon mutants with altered sensitivity to the compound. In conclusion, our results show that SPI031 exerts its antimicrobial activity by causing membrane damage, making it an interesting starting point for the development of new antibacterial therapies.
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Affiliation(s)
- Evelien Gerits
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Eline Blommaert
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Anna Lippell
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Alex J. O’Neill
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Bram Weytjens
- Department of Information Technology (INTEC, iMINDS), U.Ghent, Ghent, Belgium
| | - Dries De Maeyer
- Department of Information Technology (INTEC, iMINDS), U.Ghent, Ghent, Belgium
| | - Ana Carolina Fierro
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
- Department of Information Technology (INTEC, iMINDS), U.Ghent, Ghent, Belgium
| | - Kathleen Marchal
- Department of Information Technology (INTEC, iMINDS), U.Ghent, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, U.Ghent, Ghent, Belgium
| | - Arnaud Marchand
- CISTIM Leuven vzw, Bio-Incubator, KU Leuven, Leuven, Belgium
| | - Patrick Chaltin
- CISTIM Leuven vzw, Bio-Incubator, KU Leuven, Leuven, Belgium
- Centre for Drug Design and Discovery (CD3), Research and Development, KU Leuven, Leuven, Belgium
| | - Pieter Spincemaille
- Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
| | | | - Karin Thevissen
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Bruno P. A. Cammue
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
- Department of Plant Systems Biology, VIB, Ghent, Belgium
| | - Toon Swings
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Veerle Liebens
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Maarten Fauvart
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
- imec, Smart Systems and Emerging Technologies Unit, Department of Life Science Technologies, Leuven, Belgium
| | | | - Jan Michiels
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
- * E-mail:
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Savage VJ, Chopra I, O’Neill AJ. Population diversification in Staphylococcus aureus biofilms may promote dissemination and persistence. PLoS One 2013; 8:e62513. [PMID: 23646129 PMCID: PMC3640034 DOI: 10.1371/journal.pone.0062513] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 03/21/2013] [Indexed: 12/26/2022] Open
Abstract
The biofilm mode of growth can lead to diversification of the bacterial population by promoting the emergence of variants. Here we report the identification and characterization of two major subpopulations of morphological variants arising in biofilms of S. aureus. One of these lacked pigmentation (termed white variants; WVs), whilst the other formed colonies on agar that were larger and paler than the parental strain (termed large pale variants; LPVs). WVs were unable to form biofilms, and exhibited increased proteolysis and haemolysis; all phenotypes attributable to loss-of-function mutations identified in the gene encoding the alternative sigma factor, sigB. For LPVs, no differences in biofilm forming capacity or proteolysis were observed compared with the parental strain. Genetic analysis of LPVs revealed that they had undergone mutation in the accessory gene regulator system (agrA), and deficiency in agr was confirmed by demonstrating loss of both colony spreading and haemolytic activity. The observation that S. aureus biofilms elaborate large subpopulations of sigB and agr mutants, both genotypes that have independently been shown to be of importance in staphylococcal disease, has implications for our understanding of staphylococcal infections involving a biofilm component.
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Affiliation(s)
- Victoria J. Savage
- Antimicrobial Research Centre, School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Ian Chopra
- Antimicrobial Research Centre, School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Alex J. O’Neill
- Antimicrobial Research Centre, School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
- * E-mail:
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Abstract
Objectives To investigate the development of mutational resistance to antibiotics in staphylococcal biofilms. Methods Mutation frequencies to resistance against mupirocin and rifampicin were determined for planktonic cultures and for biofilms generated using either a novel static biofilm model or by continuous flow. DNA microarray analysis was performed to detect differences in transcriptional profiles between planktonic and biofilm cultures. Results The mutability of biofilm cultures increased up to 60-fold and 4-fold for S. aureus and S. epidermidis, respectively, compared with planktonic cultures. Incorporation of antioxidants into S. aureus biofilms reduced mutation frequencies, indicating that increased oxidative stress underlies the heightened mutability. Transcriptional profiling of early biofilm cultures revealed up-regulation of the superoxide dismutase gene, sodA, also suggestive of enhanced oxidative stress in these cultures. The addition of catalase to biofilms of S. aureus SH1000 reduced mutation frequencies, a finding which implicated hydrogen peroxide in increased biofilm mutability. However, catalase had no effect on biofilm mutability in S. aureus UAMS-1, suggesting that there is more than one mechanism by which the mutability of staphylococci may increase during the biofilm mode of growth. Conclusion Our findings suggest that biofilms represent an enriched source of mutational resistance to antibiotics in the staphylococci.
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Affiliation(s)
- Victoria J. Ryder
- Antimicrobial Research Centre and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Ian Chopra
- Antimicrobial Research Centre and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Alex J. O’Neill
- Antimicrobial Research Centre and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- * E-mail:
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McPhillie MJ, Trowbridge R, Mariner KR, O’Neill AJ, Johnson AP, Chopra I, Fishwick CWG. Structure-based ligand design of novel bacterial RNA polymerase inhibitors. ACS Med Chem Lett 2011; 2:729-34. [PMID: 24900260 DOI: 10.1021/ml200087m] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 07/29/2011] [Indexed: 11/28/2022] Open
Abstract
Bacterial RNA polymerase (RNAP) is essential for transcription and is an antibacterial target for small molecule inhibitors. The binding region of myxopyronin B (MyxB), a bacterial RNAP inhibitor, offers the possibility of new inhibitor design. The molecular design program SPROUT has been used in conjunction with the X-ray cocrystal structure of Thermus thermophilus RNAP with MyxB to design novel inhibitors based on a substituted pyridyl-benzamide scaffold. A series of molecules, with molecular masses <350 Da, have been prepared using a simple synthetic approach. A number of these compounds inhibited Escherichia coli RNAP.
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Affiliation(s)
- Martin J. McPhillie
- School of Chemistry and ‡Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Rachel Trowbridge
- School of Chemistry and ‡Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Katherine R. Mariner
- School of Chemistry and ‡Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Alex J. O’Neill
- School of Chemistry and ‡Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - A. Peter Johnson
- School of Chemistry and ‡Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Ian Chopra
- School of Chemistry and ‡Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Colin W. G. Fishwick
- School of Chemistry and ‡Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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Hurdle JG, O’Neill AJ, Mody L, Chopra I, Bradley SF. In vivo transfer of high-level mupirocin resistance from Staphylococcus epidermidis to methicillin-resistant Staphylococcus aureus associated with failure of mupirocin prophylaxis. J Antimicrob Chemother 2005; 56:1166-8. [PMID: 16275681 PMCID: PMC3319406 DOI: 10.1093/jac/dki387] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES We examined the molecular basis of the emergence of mupirocin resistance in a methicillin-resistant Staphylococcus aureus (MRSA) strain colonizing a nursing home resident undergoing mupirocin prophylaxis. PATIENT AND METHODS A persistent carrier of mupirocin-susceptible MRSA participated in a trial of mupirocin for nasal decolonization among nursing home residents. During prophylaxis a high-level mupirocin-resistant MRSA emerged in the nasal isolates from this patient. S. aureus and coagulase-negative staphylococci were isolated prior to, during and after 14 days of mupirocin treatment. The staphylococcal isolates and their plasmids were examined by molecular genetic methods. RESULTS All mupirocin-susceptible and -resistant MRSA isolates possessed the same genotype. The patient was also colonized by a single mupirocin-resistant Staphylococcus epidermidis strain. The mupirocin-resistant MRSA and S. epidermidis strains harboured identical plasmids that carried the mupA determinant and genes for conjugative DNA transfer in staphylococci. These plasmids could be transferred in vitro from both clinical isolates to S. aureus RN2677. CONCLUSIONS The MRSA strain contained a conjugative plasmid expressing mupA that was identical with that found in the S. epidermidis strain which colonized the patient. These findings suggest that transfer of mupA from S. epidermidis to MRSA probably occurred during mupirocin prophylaxis.
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Affiliation(s)
- Julian G. Hurdle
- School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK
| | - Alex J. O’Neill
- School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK
| | - Lona Mody
- Division of Geriatric Medicine, Department of Internal Medicine, Veterans Affairs Ann Arbor Healthcare System, The University of Michigan Medical School, Ann Arbor, MI, USA
| | - Ian Chopra
- School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK
| | - Suzanne F. Bradley
- Division of Geriatric Medicine, Department of Internal Medicine, Veterans Affairs Ann Arbor Healthcare System, The University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Infectious Diseases, Department of Internal Medicine, Veterans Affairs Ann Arbor Healthcare System, The University of Michigan Medical School, Ann Arbor, MI, USA
- Correspondence address. GRECC 11G, Veterans Affairs Ann Arbor Healthcare System, 2215 Fuller Road, Ann Arbor, MI 48105, USA. Tel: +1-734-761-7686; Fax: +1-734-761-7489;
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