Effect of biocides commonly used in the hospital environment on the transfer of antibiotic-resistance genes in Staphylococcus aureus

The effect of sub-minimal inhibitory concentrations of biocides, commonly u sed in the hospital environment, on the conjugation and transduction of pla smid pWG613 was investigated in three strains of Staphylococcus aureus. The highest transfer frequency was obtained in the conjugation experiments. A low concentration of povidone-iodine was found to significantly reduce tran sfer frequency by 10-fold in S. aureus SAU3/13136 mating, while other bioci des had no effect at low concentrations. Cetrimide (0.0001%) was found to i ncrease significantly transduction efficiency in S. aureus RF2 when the bio cide was included in the recovery media. A low concentration of chlorhexidi ne or povidone-iodine reduced transduction efficiency in the same recipient . This study showed that reduction in transduction efficiency was caused by the direct effect of biocides on the recipient strains rather than on the phage 80 alpha particles. (C) 1999 The Hospital Infection Society.