In vitro efficacy of povidone-iodine solution and cream against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged worldwide as a significant and difficult-to-treat source of nosocomial infection, emphasizing the ever-present need for reliable and effective antisepsis. Betadine Solution (10% povidone-iodine; PVP-I) and Betadine Cream (5% povidone-iodine) are broad-spectrum microbicides widely used for topical cleansing, wound treatment, and antisepsis. There have been no reports of bacterial resistance to Betadine preparations. In the present study in vitro killing times were determined for PVP-I solution and PVP-I cream against five hospital isolates of MRSA and one methicillin-sensitive strain (MSSA). Isolates were incubated for 24 hours in trypticase soy broth and 0.5 ml, containing 10(6)-10(7)/ml bacteria, was then removed and added to each test agent containing PVP-I. At intervals of 30 seconds, 1 min, 2 min, 3 min, 5 min, 10 min, and 15 min, 10 microliters aliquots were removed and added to 10 ml of culture broth containing 0.1% sodium thiosulphate, the neutralizing agent for PVP-I. After neutralization the samples were incubated for 48 hours and then observed for growth (turbidity) or its absence. PVP-I solution was effective against all isolates, killing each strain within 30 seconds. PVP-I cream killed four of the MRSA isolates within 30 seconds, and required a 2-3 minute killing time for one strain of MRSA and the strain of MSSA. These results are supported by four published in vitro studies which show that PVP-I is highly effective in killing MRSA. In addition, each study shows that PVP-I is more effective than chlorhexidine against MRSA.