Characterization of staphylococci contaminating automated teller machines in Hong Kong

Environmental staphylococcal contamination was investigated by culture of 400 automated teller machines (ATMs). Isolates were characterized for antibiotic and antiseptic susceptibility, carriage of antiseptic resistance genes (QAC genes), and spa types. MRSA, which was similar to local clinical isolates, was present on two (0.5%) of the 62 (15.5%) ATMs that yielded Staphylococcus aureus. QAC genes were more common in coagulase-negative staphylococci (qacA/B 26.0%, smr 14%) than S. aureus (11.3% qacA/B, 1.6% smr). QAC-positive isolates had significantly higher minimum inhibitory concentrations/minimum bactericidal concentrations to benzalkonium chloride and chlorhexidine digluconate. QAC gene presence was significantly associated with methicillin and tetracycline resistance. Survival of staphylococci, including MRSA, on common access sites may be facilitated by low disinfectant concentrations, which select for disinfectant-tolerant strains, while co-selecting for antibiotic-resistance determinants. Disinfection procedures should be performed correctly to help prevent spread of resistant pathogens from reservoirs in the community.