MULTIDRUG-RESISTANCE TO ANTISEPTICS AND DISINFECTANTS IN COAGULASE-NEGATIVE STAPHYLOCOCCI

The occurrence of resistance to antiseptics and disinfectants in clini cal isolates of coagulase-negative staphylococci (CNS) was examined. O f 164 clinical strains of CNS isolated in the early 1980s, 65 were res istant to cationic antimicrobial compounds such as cetyltrimethylammon ium bromide. Further characterisation of 40 resistant isolates by DNA- DNA hybridisation analysis and phenotypic resistance studies revealed that this resistance was mediated by the multidrug export genes qacA a nd qacC, characterised previously in Staphylococcus aureus. Of the res istant CNS isolates, 50 % contained only qacA, 10 % contained only qac C, and the remaining 40 % contained both qacA and qacC. Both qacA and qacC genes resided on plasmids in all cases, with qacA located on plas mids of > 10 kb, whereas qacC was located primarily on plasmids of 2-3 kb. Representative qacA and qacC plasmids were characterised by restr iction endonuclease mapping, and were found to be similar in some case s, but different in others, to those plasmids on which these genes are found in S. aureus.