Inactivation of Cryptosporidium parvum oocyst infectivity by disinfection and sterilization processes

Background: Cryptosporidium parvum is a common cause of self-limited gastro enteritis in the normal host but may cause severe disease in immunocompromi sed persons. Person-to-person transmission has been well documented in hous eholds, child care centers, and hospitals. Because contaminated environment al surfaces and medical devices such as endoscopes may play a role in disea se transmission, we studied the susceptibility of C parvum to chemical agen ts commonly used for disinfection and evaluated the efficacy of sterilizati on processes. Methods: Seven disinfectants were studied at their use dilution using a sus pension test. Antimicrobial activity was assessed with the use of a cell in fectivity assay. Results: All sterilization processes tested (steam, ethylene oxide, Sterrad 100) inactivated 3 logs or greater of C parvum. The only liquid disinfecta nt/sterilant able to inactivate greater than 3 logs of C parvum was 6% and 7.5% hydrogen peroxide. Agents that did not completely inactivate C parvum included hydrogen peroxide at lower concentrations or exposure times, perac etic acid, sodium hypochlorite, a phenolic, a quaternary ammonium compound, 2% glutaraldehyde, and ortho-phthalaldehyde. Conclusions: Most high-level disinfectants used on endoscopes have limited efficacy against C parvum. However, the infectivity of C parvum on dry surf aces decreases rapidly. Therefore, current cleaning and high-level disinfec tion guidelines are adequate to prevent nosocomial transmission of C parvum by means of endoscopes.