MRSA and CA MRSA the dominant SA infections
The incidence of MRSA in our population increased from 12% of S. aureus isolates in 1998 to 43% in 2003. In 2003, MRSA was cultured from 76 different patients. Isolates of MRSA were often resistant to erythromycin (91%), although resistance to other agents was less common: Ciprofloxacin (14%), levofloxacin (14%), clindamycin (3%), tetracycline (3%), and trimethoprim sulfamethoxazole (1%). No isolates were resistant to vancomycin, gentamicin, nitrofurantoin, or rifampin. Six CA-MRSA isolates were compared by pulsedfield gel electrophoresis (PFGE). Five were PFGE type USA300, and one was PFGE type USA100, based on the U.S. Centers for Disease Control and Prevention (CDC) classification scheme. The five USA300 isolates carried SCCmec type IV, and the USA100 carried SCCmec II. None of the isolates were positive by PCR for genes encoding enterotoxins A-E and H, or toxic shock syndrome toxin (TSST-1), but the five USA300 isolates carried the gene coding for Panton-Valentine leukocidin toxin. Conclusions: The incidence of MRSA at our institution is increasing. Isolates of MRSA show resistance patterns and microbiologic characteristics consistent with CA-MRSA isolates from the United States. Clinicians should consider the possibility of CA-MRSA in patients with softtissue infections who do not respond to initial therapy with beta-lactam antimicrobial agents.
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