Clinical Characteristics, Antibiotic Resistance and Molecular Typing of Methicillin-Resistant Staphylococcus aureus in a Teaching Hospital at South Taiwan

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has become an issue of public health worldwide. The clinical features, molecular epidemiology and antibiotic resistance of MRSA isolates from South Taiwan from January to December 2009 were collected and analyzed.
Methods: A total of 439 patients were invited to participate in this investigation. Antibiotic resistance was assessed by broth microdilution and pulsed-field gel electrophoresis (PFGE) was performed to identify the molecular genotypes.
Results: Among 439 culture-proven S. aureus isolates, MRSA accounted for 47.8% (210/439). The remaining 52.2% (229/439) isolates were methicillin-susceptible Staphylococcus aureus (MSSA). MRSA isolated from intensive care unit (ICU) were significantly more than MSSA and the percentage of MRSA strains isolated from the respiratory tract was significantly higher than that of MSSA. The resistant rates of MRSA to penicillin, ampicillin/sulbactam, clindamycin and erythromycin were over 80% as no MRSA isolates were resistant to vancomycin, linezolid and teicoplanin. Antimicrobial data of MRSA strains were categorized into 10 patterns, of which 5 main patterns accounted for 95.7% (n=201). PFGE characterization of MRSA was grouped into 20 genotypes (A through T). Among 20 major pulsotypes, clusters A, E, J, and N of MRSA isolates were associated with clinical and antimicrobial importance.
Conclusion: This study revealed crucial information of MRSA typing and essential connections among clinical characteristics, antimicrobial patterns and MRSA pulsotypes. The PFGE pulsotype may be coupled to distinct antibiotic-resistant patterns, special specimen sources and specific hospital department where MRSA isolated. The results can be regionally used in infection control and antibiotic stewardship of MRSA.