High prevalence of qacA/B carriage among clinical isolates of meticillin-resistant Staphylococcus aureus in Malaysia.

The minimum inhibitory concentrations (MICs) of 60 meticillin-resistant Staphylococcus aureus (MRSA) isolates from Malaysia to three antiseptic agents - benzalkonium chloride (BZT), benzethonium chloride (BAC) and chlorhexidine digluconate (CHG) - were determined. All isolates had MICs ranging from 0.5 to 2 mg/L. Antiseptic resistance genes qacA/B and smr were detected in 83.3% and 1.6% of the isolates, respectively. Carriage of qacA/B correlated with reduced susceptibility to CHG and BAC. This is the first report of the prevalence of qacA/B and smr gene carriage in Malaysian MRSA isolates, with a high frequency of qacA/B carriage. The presence of these antiseptic resistance genes and associated reduced susceptibility to antiseptic agents may have clinical implications.