Abstract
Purpose :
In clinical practice, topical ophthalmic antibiotics are commonly prescribed for numerous indications such as bacterial conjunctivitis, keratitis, blepharitis, dacryocystitis and also as prophylactic treatment after ocular surgeries. Due to the anatomical connection through the nasolacrimal duct it is possible that antibiotic eye drops also have an effect on the nasal and pharyngeal bacterial composition. This was investigated in the present study.
Methods :
Twenty healthy volunteers were randomized into four treatment groups to receive different antibiotic eye drops or topical lubricants as control. Five subjects received gentamicin eye drops, 5 received ciprofloxacin eye drops, 5 received povidone eye drops unpreserved and 5 received povidone eye drops preserved with benzalkonium chloride (BAC). Subjects self-administered the assigned eye drops 4 times daily for one week. Nasal and pharyngeal swabs were taken before the first administration and after the last dose. Illumina next-generation sequencing (NGS) based 16S rRNA analysis was performed on all samples to gain information about the nasal and pharyngeal bacterial microbiome. Bacterial richness data were provided as operational taxonomic units (OTUs).
Results :
None of the administered eye drops had a relevant effect on the pharyngeal microbiome. In contrast, a numerical increase in bacterial richness in nasal swabs was found after antibiotic treatment. In particular, nasal bacterial richness increased from 163 ± 30 to 243 ± 100 OTUs with gentamicin treatment (p = 0.06) and from 114 ± 17 to 144 ± 45 OTUs with ciprofloxacin treatment (p = 0.31). In the povidone group, nasal bacterial richness only changed from 177 ± 41 to 186 ± 63 OTUs (p = 0.88) while in the povidone + BAC group, it almost remained identical (148 ± 50 vs. 148 ± 39 OTUs, p= 1.0).
Conclusions :
Although not statistically significant, the results of the present study point towards a potential effect of topical antibiotics on the nasal bacterial flora, while no effect on the pharyngeal microbiome was found. To confirm these results, larger studies including more subjects are needed.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.