The results in this study showed that some staphylococci harboured both disinfectant (QAC, bemzalkonium chloride) and antibiotic resistance (penicillin) on the same plasmid. They conclude that presence of both resistance determinants could lead to co-selection during antimicrobial therapy or disinfection in hospitals or in food industries. Microbial Drug Resistance 2001;7:363-371.