PRELIMINARY REPORT OF SCCMEC-TYPES AND ANTIMICROBIAL SUSCEPTIBILITIES OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS ISOLATES FROM A UNIVERSITY HOSPITAL IN THAILAND

Methicillin-resistant Staphylococcus aureus (MRSA) has spread worldwide. It is a major cause of hospital-acquired infections in most hospitals for nearly half century. The present study was conducted to examine the antimicrobial suscepti- bilities and staphylococcal cassette chromosome mec (SCCmec)-type for MRSA iso- lates from 237 patients treated at Srinagarind Hospital between September 2002 and August 2003. Antimicrobial susceptibility testing for all isolates was performed using an agar dilution method and SCCmec-types of 81 representatives from 237 isolates were determined using multiplex PCR. The minimum inhibitory concen- tration (MIC) ranges for the MRSA isolates were as follows: cefazolin 8 to ≥ 64; erythromycin ≤ 0.5 to ≥ 64; gentamicin ≤ 0.5 to ≥ 64; imipenem ≤ 0.5 to > 16; ofloxacin ≤ 0.5 to ≥ 64; oxacillin 16 to ≥ 64; tetracycline 2 to ≥ 64 and vancomycin ≤ 0.5 to 2 µg/ml. All MRSA isolates were susceptible to vancomycin, but only 0.4% to 8.9% was susceptible to the remaining antimicrobial agents. Of the 81 isolates tested, 2 types of SCCmec were found (76 with type III and 2 with type II) and no mecA gene was detected in 3 isolates. Sixty-seven of the 78 isolates carried the mercury-resistant operon. The multilocus sequence type in isolates with type III SCCmec was ST239 and in isolates with type II SCCmec was ST5.