Bacterial Communities Identified by Standard Culture and 16S rRNA Amplicon Sequencing in Ophthalmic Preservative-Free Dexamethasone SP Used in Canine Cataract Surgery.

Preservative-free dexamethasone SP shows minimal bacterial contamination; unlikely causative of post-surgical fibrin webs.

This study investigated bacterial contamination in preservative-free dexamethasone sodium phosphate (dexamethasone SP) used in canine cataract surgery, employing both culture-dependent and molecular methods. Thirty samples from five batches across three commercial brands were analyzed. Culture results showed low contamination rates (0/10 Auromedics, 1/10 Fresenius Kabi, 4/10 Somerset), with identified bacteria likely representing plating contaminants rather than product contamination. 16S rRNA sequencing revealed nine common bacterial families across samples without significant brand-specific differences. Endotoxin levels were below the assay detection limit (0.5 EU/mL) in all samples. Differential abundance analysis identified Lactococcus and Acetitomaculum as biomarkers for Auromedics and Solobacterium for Somerset products. These findings suggest that bacterial contamination in commercial preservative-free dexamethasone SP products is minimal and unlikely to be clinically significant. However, the presence of detectable bacterial DNA, despite low culture positivity, warrants continued monitoring. The study provides reassurance regarding product safety while highlighting the importance of maintaining sterile technique during ophthalmic surgery to prevent fibrin web formation.

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