The efficacy of three common hospital liquid germicides to inactivate Cryptosporidium parvum oocysts

We evaluated three commonly used hospital disinfectants against three conce ntrations of Cryptosporidium parvum oocysts (1.5 x 10(6), 1.5 x 10(5), 1.5 x 10(4)). A 10% phenol product, a 10% povidone-iodine product and a 2.5% gl utaraldehyde product were tested against Cryptosporidium parvum oocysts wit hout organic load. In-vitro excystation was used to determine viability and a cell culture assay was used to determine infectivity of germicide-treate d oocysts. A 2.5% glutaraldehyde product was the most effective in halting excystation of sporozoites and infection in cell monolayers. However, this occurred only at the longest exposure time of 10 h and with the lowest conc entration of oocysts (1.5 x 10(4)). The 10% phenol product and the 10% povi done-iodine product also decreased excystation, but were unable to halt inf ection. Although the ability of C. parvum to withstand chemical treatment i s well known, the ability of oocysts to remain viable and infectious after a 10 h treatment in glutaraldehyde is cause for concern. Endoscopic equipme nt that may come into contact with these organisms cannot be immersed into glutaraldehyde for this length of time due to its corrosive nature. Thus, t he results of this research are cause for concern in hospital disinfection units.