Effectiveness Of Topical Antiseptics In Reducing Conjunctival Bacterial Flora: Randomized Clinical Trial.

To evaluate the effectiveness of two topical antiseptics, povidone-iodine (PVI) and chlorhexidine (CHX) in reducing conjunctival bacterial flora.

Single-center, prospective, randomized clinical trial. 70 patients undergoing cataract surgery were randomly divided in two groups: 35 patients used PVI 0.66% 4 times daily starting 3 days before surgery; 35 patients used CHX 0.02% with the same posology. The contralateral eye was considered as control. Conjunctival swabs of both eyes at the baseline (T0) and after three days of treatment (T1) were collected all before cataract surgery.

An eSwab with 1mL of Liquid Amies Medium (Copan Brescia, Italy) was used. DNA was extracted with a QIAamp DNA Microbiome Kit. 16S rDNA gene was amplified. Libraries were pooled to obtain the final concentration at 26 pM. Template preparation was performed with Ion Chef. Sequencing of the amplicon libraries was carried out on 530 chip using the Ion Torrent S5 system. Raw reads were analyzed with GAIA (v 2.02). The richness and Shannon alpha diversity metrics, as well as Bray–Curtis beta diversity values, were computed with the R package phyloseq. The identification of ECSTs (Eye Community State Type) was carried out with the R package cluste. Principal coordinate analysis (PCoA) was performed using the function plot_ordination.

Partial results are available. 84 eye microbiome samples were analyzed. Taxonomic composition eye microbiota by gender has been examined. Furthermore, microbiota of the 2 groups after treatment has been reported. The vast majority of samples showed a reduction in Staphylococcus, Bacillus, Pseudomonas and Corynebacterium. We found an average of 88 genera with an average Shannon index of 0.65. ECTSs were characterized accordingly in each group (ECTS-1 and ECTS-2). The results will be presented as estimates of the effects (ratios or fold changes) and corresponding 95% confidence intervals. All tests will be two-sided and a 5% significance level will be used. Analyzes will be conducted using R (4.0.2 or later) and STATA (14.0).

The preliminary results show that topical antiseptics were able to reduce conjunctival bacterial microbiota. PVI group lead to ECST-1 ehole CHX to ECST-2. All results will bring high quality evidence to guide prescription of antibiotic in preparation to intraocular procedure as cataract surgery and intravitreal injection for lowering the risk of ocular infection.