In Vitro Susceptibility of Bacillus cereus Spores of Blood Isolates and Healthy Skin Isolates to 10% Povidone-iodine

Abstract

The susceptibility of Bacillus cereus spores to 10% povidone-iodine was measured at 0°C, 20°C, and 37°C, respectively. The spores of 15 B. cereus blood isolates and 15 isolates from healthy adult skin, respectively, were used for the measurement. The spore solution was prepared 9 days after the culture of B. cereus on NGKG plates, and spore formation was confirmed microscopically. No B. cereus strain in the spore form was highly resistant to any conditions of 10% povidone-iodine treatment. Approximately 99% of the spores of most strains were killed after a 5-min treatment with 10% povidone-iodine irrespective of treatment temperature, whereas 1% of spores survived a 30-min treatment. The spores of 5 blood isolates and 3 healthy skin isolates were more sensitive to 10% povidone-iodine, and only 0.1% of the spores survived the 5-min treatment. No apparent differences in susceptibility to povidone-iodine between the blood and skin isolates were observed. From these results, 5-min treatment using 10% povidone-iodine for skin disinfection is applicable when contamination of B. cereus spores on the skin is expected to be mild or low.