Identification of the plasmid-encoded qacA efflux pump gene in meticillin-resistant Staphylococcus aureus (MRSA) strain HPV107, a representative of the MRSA Iberian clone.

Meticillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial bacterium for which prevention and control measures consist mainly of the application of biocides with antiseptic and disinfectant activity. In this study, we demonstrated the presence of the plasmid-located efflux pump gene qacA in MRSA strain HPV107, a clinical isolate representative of the MRSA Iberian clone. The existence of efflux activity in strain HPV107 due to the QacA pump was also established and this QacA efflux activity was linked with a phenotype of reduced susceptibility towards several biocide compounds. No association could be made with antibiotic resistance. This work emphasises the potential of QacA pump activity in the maintenance and dissemination of important MRSA strains in the hospital setting and, increasingly, in the community.