Preliminary report of SCCmec-types and antimicrobial susceptibilities of methicillin-resistant Staphylococcus aureus isolates from a university hospital in Thailand

Abstract

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 susceptibilities and staphylococcal cassette chromosome mec (SCCmec)-type for MRSA isolates 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 concentration (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.