Current update on methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin and chlorhexidine in Srinagarind Hospital

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) has been an important problem in hospital and community-acquired infections, resulting in requirement of vancomycin for clinical treatment. Nowadays, infections caused by MRSA with reduced susceptibility to vancomycin have been reported increasingly. These strains could not be detected by routine disc diffusion method. Therefore, it was necessary to test vancomycin susceptibility of MRSA isolates by determining the minimum inhibitory concentration (MIC). Moreover, there have been reports of MRSA resistant to disinfectants such as chlorhexidine, which has been commonly used for infection control and reducing the spread of MRSA in the hospital. The aim of this study was to investigate the prevalence of vancomycin and chlorhexidine resistance among MRSA isolates of patients in Srinagarind Hospital, Khon Kaen Province. A total of 100 non-repetitive MRSA isolates were studied. The chlorhexidine and vancomycin susceptibility tests were performed by an agar dilution method. The results showed that the MIC values of vancomycin for 38, 64 and 2 MRSA isolates were 1, 2 and 4 µg/ml respectively. The MIC values of chlorhexidine for 30 MRSA isolates were > 4 µg/ml (high level) whereas those for the remaining 70 isolates were < 2 µg/ml (low level). Though most of the tested MRSA was susceptible to vancmycin but the majority was in the high MIC level (close to the border line). In addition, 2 % of these isolates were vancomycin intermediately susceptible to vancomycin and 30 % had reduced susceptibility to chlorhexidine. In the present study, no isolate had co-resistance to both agents. This information would be useful for MRSA infection control and management.