Bacterial contamination of extraocular fluid and antibiotic susceptibility during cataract surgery and vitrectomy

Abstract

Purpose : There are studies reporting contamination of extraocular fluid at the end of surgery, but change of contamination rate during surgery and antibiotic susceptibility had been studied insufficiently. We performed a retrospective interventional clinical study to confirm the extent of bacterial contamination and antibiotic susceptibility of extraocular fluid at the beginning and end of cataract surgery and vitrectomy after disinfection.

Methods : Medical records of consecutive patients who underwent cataract surgery or vitrectomy with extraocular fluid culture were reviewed retrospectively. Patients with infection, recent ocular trauma, immunocompromised state, or antibiotics treatment were excluded. During surgical skin preparation, povidone-iodine was poured through palpebral fissure. At the initiation, a flush of povidone-iodine and BSS irrigation were done in the conjunctival sac. 1ml of Extraocular fluid was collected at the beginning (Pre-fluid) and end of the surgery (Post-fluid). Each half of sample were collected from both canthi while instilling BSS. The samples were injected into the BacT/Alert PF pediatric blood culture bottle. Bacterial identification and antibiotics susceptibility test were performed. Culture results and antibiotic susceptibility were investigated. The χ² test or Fisher's exact test was performed to determine differences in results depending on surgical method or timing of sample collection.

Results : One hundred thirty-three eyes were enrolled, including 40 eyes with cataract surgery and 93 eyes with vitrectomy. There were 20 (15%) positive cultures in Pre-fluid and 51 (38%) in Post-fluid. The positive culture rate was higher in Post-fluid (p<0.001, χ² test). The following organisms were frequently identified: Staphylococcus epidermidis (15) and S. aureus (4) in Pre-fluid and S. epidermidis (37) and S. lugdunensis (5) in Post-fluid. In each result of cataract surgery and vitrectomy, S. epidermidis was the most frequent organism in both Pre-and Post-fluid. Most strains didn’t showed resistance to vancomycin or 3^rd generation cephalosporin.

Conclusions : Despite disinfection in vitrectomy and cataract surgery, bacterial contamination may occur at the surgical site, and bacterial contamination was confirmed more frequently at the end of surgery. The most common organism was S. epidermidis, and most of them were susceptible to empirical antibiotics.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.