Survival of gram-positive spore-forming bacteria including Bacillus cereus after hand washing using alcohol-based handrub

Hand washing is the most fundamental method for preventing infection. Currently, hand washing with an alcohol-based handrub is the international gold standard method. However, in our study we found many samples of ineffective hand washing using an alcohol-based handrub. The rates of ineffective samples were 10.4% (5/48) in 2004 and 34.3% (12/35) in 2005. We examined the morphology by Gram staining and biochemical properties of the bacteria which remained after hand washing in 2005. Their colonies were divided into 3 groups (round colonies, irregular-shaped and diffusive colonies). The round colonies were considered Staphylococcus spp., and the irregular-shaped colonies or diffusive colonies were considered Gram-positive spore-forming bacteria. In the 12 ineffective hand washing samples (more than the same number of bacteria colonies as before hand washing, or ≥300), there were 3 samples considered to be the result of the survival of Staphylococcus spp., and 9 samples considered to be the result of the survival of Gram-positive spore-forming bacteria including Bacillus cereus. Based on these results, we should take careful measures, such as wearing sterile gloves if necessary. We should never be overconfident regarding the effect of hand washing.