Molecular epidemiology of community-acquired methicillin-resistant Staphylococcus aureus bacteremia in a teaching...

Methicillin-resistant Staphylococcus aureus (MRSA) is a key nosocomial pathogen globally. Community-acquired MRSA (CA-MRSA) infections have become a growing problem in recent years. The purpose of this 4-year retrospective study was to analyze the molecular epidemiology and susceptibility pattern of isolates from adults (> or =18 years of age) with CA-MRSA bacteremia in northern Taiwan.

Molecular epidemiology of CA-MRSA isolates was analyzed by pulsed-field gel electrophoresis. Antimicrobial susceptibility was tested by the disk diffusion method and the minimal inhibitory concentration was determined by Etest.

Thirty eight patients with CA-MRSA bacteremia were enrolled. Thirty one CA-MRSA isolates were available for further molecular typing and susceptibility testing. A total of 13 distinct genotypes were identified and 48.4% (15/31) of the isolates were found to belong to genotype A. Genotype A CA-MRSA isolates were closely associated with the nosocomial strains. All CA-MRSA isolates were multidrug resistant (19.4% susceptible to clindamycin and 25.8% to trimethoprim-sulfamethoxazole) and consistent susceptibility was only observed to glycopeptides, rifampin, and linezolid.

This study demonstrated that although CA-MRSA genotypes were heterogeneous, the predominant genotype that was circulating in our community was genotype A. Also, the multidrug resistance of CA-MRSA might be connected to the spreading of nosocomial strains in the community.