INVITRO EVALUATION OF POVIDONE IODINE AND CHLORHEXIDINE AGAINST METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

The in-vitro activity of povidone-iodine (PVP-I) and chlorhexidine (CHX) against 33 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) was evaluated by a quantitative suspension test method. Bactericidal potency was measured by the logarithmic reduction factors (LRFs) achieved with each strain, tested at dilutions 25-800 over exposure times 30-300 s using a challenge of approximately 107 colony forming units (cfu)ml-1. The mean LRFs achieved over all dilutions, times and strains were significantly higher for PVP-I than CHX. PVP-I exhibited a superior killing effect whether measured by rate of kill or final LRF achieved. This difference was highly significant as judged by analysis of variance (P <0 ·001). Full efficacy of an antiseptic has been defined as a safe LRF greater than five. Over the dilution range 25-200 this was achieved by CHX with only three of 33 strains. In contrast, PVP-I achieved full efficacy with all 33 strains. © 1992.