title: The in-vitro activity of povidone-iodinecream against Staphylococcus aureus and its bioavailability in nasal secretions.
abstract: Due to the emergence of mupirocin-resistance in some epidemic strains of methicillin resistant Staphylococcus aureus (EMRSA) and the appearance of EMRSA with intermediate resistance to vancomycin, we evaluated the in-vitro activity of 5% povidone-iodine ('Betadine') cream as a possiblealternative to mupirocin for the elimination of nasal carriage of S. aureus. As judged by enrichment culture, povidone-iodine was bactericidal against three mupirocin-sensitive strains of S. aureus from nasal carriers, and against mupirocin-resistant and -sensitive strains of EMRSA types 3, 15 and 16, after incubation with povidone-iodine for 1.0 min at 32 degrees C. Mupirocin nasal ointment did not prevent growth after 180 min incubation. In a quantitative suspension test, 1:100 dilution of povidone-iodine cream completely eliminated an inoculum of 10(8)cfu/mL of all nine test organisms after incubation at 32 degrees C for 1.0 min, and 1:1000 dilution reduced cfu, by a factor of 10(5). After direct inoculation of the povidone-iodine cream to give 10(5)cfu/g, none of the test strains were recoverable after 30 s, giving a killing rate of approximately 10(4)cfu/s; for mupirocin nasal ointment, the maximum reduction of mupirocin-sensitive strains was ten fold after 3 h. Povidone-iodine activity was not detectable in sensitivity-testing agar, although 0.025% of povidone-iodine was detectable in a 15% nutrient strength tryptone soya agar. Using this minimal medium, the addition of nasal secretions (from any of 11 samples) reduced the activity of povidone-iodine by 80-90%, but mupirocin activity was unaffected. One millilitre of nasal secretions inactivated the equivalent of approximately 22.5 mg of povidone-iodine. These results suggest that povidone-iodine cream may have a role in the prevention of colonization and infection caused by MRSA, including mupirocin-resistant strains.
authors.affiliation: Dulwich Public Health Laboratory and Medical Microbiology, Guy's, King's and St Thomas' School of Medicine, King's Denmark Hill Campus, Bessemer Road, London, UK.
authors.forename: R L
authors.initials: RL
authors.lastname: Hill
authors.forename: M W
authors.initials: MW
authors.lastname: Casewell
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000891:Anti-Infective Agents, Local / Q000493:pharmacokinetics / Q000494:pharmacology*; D001682:Biological Availability; D002353:Carrier State; D004352:Drug Resistance, Microbial; D006801:Humans; D008826:Microbial Sensitivity Tests; D016712:Mupirocin / Q000494:pharmacology; D009297:Nasal Mucosa / Q000378:metabolism; D009666:Nose / Q000382:microbiology; D011206:Povidone-Iodine / Q000493:pharmacokinetics / Q000494:pharmacology*; D013203:Staphylococcal Infections / Q000517:prevention & control; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D011206:Povidone-Iodine; D016712:Mupirocin