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

Aims/Purpose: We performed a retrospective case-series study to investigate 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. Patients with infection, recent ocular trauma, immunocompromised state, or antibiotics treatment were excluded. During surgical skin preparation, povidone-iodine (PvI) was poured through palpebral fissure was done. At the initiation, a flush of PvI and BSS irrigation was added into the conjunctival sac. 1ml of fluid was collected at the beginning (Pre-fluid) and end of the surgery (Post-fluid). 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. 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: Two hundred thirty-three eyes were enrolled, including 72 eyes with cataract surgery and 161 eyes with vitrectomy. There were 31 (13.3%) positive cultures in Pre-fluid and 71 (30.5%) positive cultures 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 (sample size N = 74), S. aureus (N = 10) and S. lugdunensis (N = 6). All types of strains didn’t showed resistance to vancomycin or 3^rd generation cephalosporin.

Conclusions: Despite disinfection in ocular 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.