Microbial contamination of eye drops

The microbial contamination of eye drops at the Eye Clinic was studied. In total, 92 eye drop bottles were examined. 43 bottles were opened and used and 49 were unopened and sealed. The contamination rate was found to be 10.2% in unopened bottles and 34.8% in opened bottles. The opened bottles had been used for two weeks. Six of the samples yielded coagulase-negative Staphylococci and nine samples yielded one or two different microorganisms. The contamination rate in bottles containing the preservative benzalkonium chloride was 34.4%. Among unopened eye drop bottles two samples yielded S. aureus, two coagulase-negative Staphylococci and one Bacillus spp.