Molecular pattern and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus isolates at a teaching hospital in Northern Taiwan.

BACKGROUND AND PURPOSE: Methicillin-resistant Staphylococcus aureus (MRSA) infection has progressively increased worldwide. Knowledge of the specific epidemiological pattern of isolates at individual hospitals is important. METHODS: MRSA bacteremia was diagnosed in a total of 68 patients from January 2002 through December 2003, stratified for drug susceptibility and molecular pattern (staphylococcal cassette chromosome mec element [SCCmec] typing and genotypes). RESULTS: SCCmec-A-positive isolates were found on polymerase chain reaction in 58 patients. The most frequent SCCmec types were III (40 cases) of which less than 5% were susceptible to other beta-lactam antibiotics and most were health care-associated, followed by SCCmec type IV (15 cases), that were demonstrated to be community-acquired. SCCmec type IV MRSA isolates were more likely to be susceptible to ciprofloxacin (93.3%), gentamicin (46.7%) and trimethoprim-sulfamethoxazole (93.3%) than type III isolates. All MRSA isolates were susceptible to glycopeptides and vancomycin (minimum inhibitory concentrations <2 microg/mL). Pulsed-field gel electrophoresis with SmaI digestion was used to fingerprint these isolates. A total of 9 genotypes with 26 type-subtypes were identified. Genotype A was the most frequent (9 subtypes) indicating that it is epidemic in this hospital. CONCLUSION: After analysis, SCCmec typing could be used to predict drug susceptibility. Specific clones of S. aureus are circulating in hospital and communities in Taiwan.