title: Differential growth of epidemic methicillin-resistant Staphylococcus aureus in vancomycin.
abstract: This study examines the ability of isolates representing the 17 epidemic methicillin-resistant strains of Staphylococcus aureus to grow in increasing levels of vancomycin. Only EMRSAs 1, 2, 8, 11, 12 and 15 showed any growth and were designated EMRSAs 1A, 2A, 8A, 11A, 12A and 15A. On population analysis, these strains all produced clones that grew on 32 microg/mL vancomycin, while EMRSA 12A and 15A grew at 128 microg/mL. This was associated with increased resistance to lysostaphin and teicoplanin, a loss of phage sensitivity and an increase in cell wall diameter. Typing by pulsed-field gel electrophoresis following SmaI digestion showed no change in EMRSA 8A and 15A, while the other EMRSAs all lost or gained at least one band. EMRSAs 1A, 2A and 15A became more resistant to methicillin, and EMRSAs 8A, 11A and 12A became less resistant to methicillin. These results suggest that more than one mechanism is responsible for this phenomenon.
authors.affiliation: Department of Medical Microbiology, Clinical Sciences Building 1, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, UK.
authors.forename: I
authors.initials: I
authors.lastname: Alshami
authors.forename: R C
authors.initials: RC
authors.lastname: Matthews
authors.forename: J F
authors.initials: JF
authors.lastname: Burnie
authors.forename: A H
authors.initials: AH
authors.lastname: Asghar
authors.forename: A M
authors.initials: AM
authors.lastname: Momenah
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003428:Cross Infection; D004196:Disease Outbreaks; D004305:Dose-Response Relationship, Drug; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000188:drug therapy; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development*; D014640:Vancomycin / Q000494:pharmacology*; D020713:Vancomycin Resistance
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin