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| Content Provider | PubMed Central |
|---|---|
| Author | Rose, Warren E. Fallon, Michael Moran, John J. M. Vanderloo, Joshua P. |
| Copyright Year | 2012 |
| Abstract | Methicillin-resistant Staphylococcus aureus (MRSA) isolates that are susceptible to vancomycin but are tolerant to its killing effect may present a potential challenge for effective treatment. This study compared the microbiologic characteristics of clinical vancomycin-tolerant (VT-MRSA) and vancomycin-susceptible (VS-MRSA) strains using phenotypic and gene regulation studies. MRSA isolates collected from vancomycin-treated patients with bacteremia over a 5-year period were analyzed for vancomycin, daptomycin, and telavancin susceptibility, as well as accessory gene regulator (agr) group and function. Vancomycin tolerance was defined by a minimum bactericidal concentration (MBC)/minimum inhibitor concentration (MIC) ratio of ≥32 mg/liter. VT-MRSA isolates were compared to VS-MRSA isolates for differences in antimicrobial susceptibility, time-kill activity, and gene expression of key cell envelope response genes vraSR, dltA, and mprF. All 115 isolates evaluated were susceptible to vancomycin, daptomycin, and telavancin. Seven isolates (6%) were VT-MRSA. agr group II was more prevalent in isolates with vancomycin MBC/MIC ratios of ≥8. In time-kill analyses, VT-MRSA had reduced vancomycin killing, but daptomycin and telavancin activities were maintained. Significantly greater gene expression was observed in VT-MRSA after 72 h of subinhibitory antibiotic exposures. Vancomycin most notably increased vraSR expression (P = 0.002 versus VS-MRSA strains). Daptomycin and telavancin increased expression of all genes studied, most significantly mprF expression (P < 0.001). Longer durations of antibiotic exposure (72 h versus 24 h) resulted in substantial increases in gene expression in VT-MRSA. Although the clinical impact of VT-MRSA is not fully recognized, these data suggest that VT-MRSA strains, while still susceptible, have altered gene regulation to adapt to the antimicrobial effects of glyco- and lipopeptides that may emerge during prolonged durations of exposure. |
| Related Links | http://dx.doi.org/10.1128/aac.00676-12 |
| Ending Page | 4427 |
| Page Count | 6 |
| Starting Page | 4422 |
| File Format | |
| ISSN | 00664804 |
| e-ISSN | 10986596 |
| Journal | Antimicrobial Agents and Chemotherapy |
| Issue Number | 8 |
| Volume Number | 56 |
| Language | English |
| Publisher | American Society for Microbiology |
| Publisher Date | 2012-08-01 |
| Access Restriction | Open |
| Rights Holder | American Society for Microbiology |
| Subject Keyword | Pharmacology (medical) Pharmacology Infectious Diseases Research in Higher Education |
| Content Type | Text |
| Resource Type | Article |
| Subject | Infectious Diseases Pharmacology Pharmacology (medical) |
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