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Optimizing the antisepsis protocol: Effectiveness of 3 povidone-iodine 1.0% applications versus a single application
Megan R Silas1, Richard M Schroeder1, Richard B Thomson1
1From the Department of Graduate Medical Education (Silas), MacNeal Hospital, Berwyn, the Department of Pathology (Thomson), NorthShore University Health System, Evanston, and the Feinberg School of Medicine (Myers), Northwestern University, Chicago, Illinois, and the Department of Ophthalmology and Visual Sciences (Schroeder), Washington University School of Medicine, St. Louis, Missouri, USA.
Purpose:
To determine the minimum effective concentration of povidone-iodine that reduces the bacterial load by 3-log10, the U.S. Food and Drug Administration requirement for antiseptic agents, and to study alternative dosing schedules of povidone-iodine to optimize its bactericidal effect.
Setting:
Microbiology Laboratory, Evanston Hospital, Evanston, Illinois, USA.
Design:
Experimental study.
Methods:
A standard 0.5 McFarland solution of Staphylococcus epidermidis was applied to blood agar plates. The plates were treated with a single application of povidone-iodine solutions from 10.0% to 0.1% to define the range of interest. Another set of plates received 3 applications of various povidone-iodine solutions. Microbial growth was evaluated after 24 hours. Standard deviations with 99.0% and 99.9% confidence intervals for each concentration were estimated and used to estimate the minimum concentration that reduced the colony counts by at least 3-log10.
Results:
Povidone-iodine at 2.5% and higher concentrations was effective in eliminating S epidermidis with a single application. Three 30-second applications of povidone-iodine at concentrations of 0.7% and higher resulted in at least a 3-log10 reduction of colonies.
Conclusions:
Povidone-iodine 5.0% has been the standard of care for preoperative ocular antisepsis for 3 decades. Povidone-iodine 0.7% was as effective as a bactericidal agent when applied multiple times. This suggests povidone-iodine 1.0%, applied in three 30-second applications for preoperative surface disinfection might be as effective for preoperative antisepsis.