Microbial Contamination of Extended Use Ophthalmic Drops in Ophthalmology Clinic

Abstract

Purpose

The objectives of this study were to determine the prevalence of microbial contamination of multi-user preserved ophthalmic drops (POD) in Ophthalmology Outpatient Clinic (OOC), to compare the rate of contamination between the dropper tip and the residual contents in the bottle, and to identify the contaminating organisms.

Methods

This was an observational cross-sectional study using a convenience sampling method conducted in the OOC of Universiti Kebangsaan Malaysia Medical Center, Malaysia. The samples of POD bottles were divided into groups obtained after 14 days (T14) and after 30 days (T30) of use. The contamination rate at the dropper tip and in the residual contents was determined and the contaminating organisms were identified.

Results

A total of 140 of 149 extended-use POD bottles were included. The prevalence of contamination was 30%. There was a statistically significant difference in the rate of contamination between samples T14 and T30 (19% and 11%, respectively; p=0.046). Proparacaine and tropicamide showed higher contamination rates in the T14 samples (p=0.027 and p=0.497, respectively) than in the T30 samples. The site of contamination was higher at the dropper tip than in the residual contents (p>0.05). Coagulase-negative Staphylococcus species were the most frequently identified contaminants (89%).

Conclusion

The dropper tip was more contaminated than the residual contents, and coagulase-negative Staphylococcus species, which are common commensal flora of the ocular conjunctiva and skin, were the most frequently identified organisms.

Keywords:

• contamination rate
• extended period
• preserved ophthalmic drops
• multi-user

Acknowledgments

We would like to thank the staff at the ophthalmology outpatient clinic of UKMMC for providing us with the samples from newly opened and used bottles of the eyedrops. The assistance of the microbiology assistant at the lab is highly appreciated. We are grateful to Dr. Wan Rozita for her help with data analysis using SPSS and to Prof. Dr. Syed Zulkifli for his help with the sample size calculation.

Disclosure

This manuscript has not been presented elsewhere. No competing interests exist for any authors.

Additional information

Funding

This study was funded by student grant under postgraduate studies from Universiti Kebangsaan Malaysia. The publication fee was funded by research grant from Universiti Malaysia Sabah.