Microbial contamination of multiple-dose preservative-free hospital ophthalmic preparations in a tertiary care hospital.

Background: It is possible that preservative-free eye drops can be contaminated. The aim of this study was to assess the incidence of microbial contamination of preservative-free hospital-prepared anti-infective eye drops and investigate factors that contribute to contamination. This finding may help to raise awareness of this problem to medical healthcare staff and patients in order to prevent the transmission of microorganisms from eye drops to the patients through treatment of pre-existing eye diseases.

Methods: Two hundred and ninety-five eye drop bottles were collected from patients attending Rajavithi Hospital Ophthalmologic outpatient and inpatient department, including both those used by patients at home and those administered in the hospital by medical staff. Samples were taken from the tips of droppers and bottles, and the residual fluid inside the bottles was then cultivated onto different culture plates. The culture results were identified and analyzed according to various factors related to both individual users and the bottles.

Results: Seven different types of eye drops were collected and 71 (24.06%) of the 295 bottles were contaminated. Vancomycin eye drops were the most contaminated. Twenty-six different types of pathogens were identified, most frequently mold (42.98%), and the amount of contamination was higher in tips than in residual fluid inside the bottle. There was no statistically significant difference in contamination between patients used eye drops collected in outpatient units (32.14%) and medical staff used eye drops collected in inpatient settings (23.22%). The only factor that was statistically significant was the number of eye drops used per person. We found that samples from patients who used only up to 2 eye drops suffered contamination (42.8%) more than those from their counterparts who used at least 3 (22.18%),  ​= ​0.02.

Conclusions: Of these preservative-free hospital preparations anti-infective eye drops, 24.06% were contaminated. The number of eye drops used per person was statistically significant in triggering contamination. There is a possibility of number of eyedrops use person may trigger contamination.