Abstract
Microbial contamination of used eyedrop preparations collected from outpatients was investigated and the proper use and storage methods to avoid contamination are discussed. At Yamaguchi University Hospital, 214 used eyedrop samples were collected from outpatients. Twelve samples (5.6%) were found to be contaminated at concentrations of 101-104 viable organisms per container. The major contaminants were glucose nonfermentative gram-negative bacilli, such an Pseudomonas spp. and Flavobacterium spp., and yeast-like fungi, such as Candida albicans. Contamination was observed in eyedrop preparations containing any of three preservatives (benzalkonium chloride, p-hydroxybenzoate esters, and chlorobutanol). On the other hand, no growth occurred when contaminants of used eyedrop samples were inoculated into the same kinds of eyedrops that had not been used. Microbial contamination of ophthalmic preparations during use could not be avoided, because the amounts of antimicrobial substances are limited by eye irritation. Insufficient selfsterilizing capacity was demonstrated for all three preservatives. However, those preservatives prevented prolification of the contaminants.
