Expression and detection of hetero-vancomycin resistance in Staphylococcus aureus.
Isolates of Staphylococcus aureus resistant to vancomycin have been reported but appear to be extremely rare. However, isolates displaying hetero-resistance to vancomycin (hVRSA) are reportedly common in parts of Japan (9.3% of MRSA isolated from a group of university hospitals). We have investigated the reliability of the proposed method for detection of hetero-resistant isolates and the ability of clinical S. aureus isolates to express vancomycin resistance. The original method for identification of hVRSA was found to have poor reproducibility and may select for, rather than detect, vancomycin resistance. There appears to be a spectrum of heterogeneity in the expression of resistance to vancomycin among S. aureus. Until there is a clearer understanding of the mechanism and control of vancomycin resistance in S. aureus, and reliable tests are devised, the clinical relevance of different degrees of hetero-resistance cannot be assessed.
Howe
R A
RA
Bristol Centre for Antimicrobial Research and Evaluation, Southmead Health Services NHS Trust and University of Bristol, Department of Microbiology, Southmead Hospital, Bristol, UK.
Wootton
M
M
Walsh
T R
TR
Bennett
P M
PM
MacGowan
A P
AP
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D015203:Reproducibility of Results; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development*; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents; D014640:Vancomycin