Microbiological profile and antibiotic resistance trends of preoperative conjunctival swabs: An 8-year retrospective analysis from a North Indian tertiary care ophthalmic center.

PURPOSE: To assess the spectrum of bacterial flora from preoperative conjunctival swabs and analyze their antimicrobial susceptibility patterns.

DESIGN

This is a retrospective observational clinical study.

METHODS

This retrospective, observational study analyzed conjunctival swab cultures collected 24-48 hours prior to elective ophthalmic surgeries at a tertiary eye care center in North India from January 2015 to December 2022. Aerobic bacterial cultures were performed using standard microbiological techniques. Isolates were identified and tested for antibiotic susceptibility using the Kirby-Bauer disk diffusion method following CLSI guidelines. Data were stratified by patient age groups and analyzed using descriptive statistics and Chi-square testing.

RESULTS

Of the 8671 conjunctival swabs analyzed, 1287 (14.8%) showed significant bacterial growth. The most prevalent isolates were Coagulase-negative Staphylococci (CoNS, 53.3%), Corynebacterium species (32.9%), and Staphylococcus aureus (10.7%). Methicillin resistance was observed in 40% of Staphylococcal isolates, with significant coresistance to fluoroquinolones, macrolides, and tetracyclines. No Vancomycin resistance was observed. Gram-negative bacteria, though infrequent (1.7%), were predominantly isolated from adult and elderly patients. Resistance trends showed a rising pattern over the 8-year period, particularly against fluoroquinolones and cefoxitin. Agewise, bacterial positivity was similar across pediatric (12.0%), adult (15.1%), and elderly (15.1%) groups (P = 0.1462).

CONCLUSION

This large-scale study highlights the predominance of CoNS and Corynebacterium in the conjunctival flora and the rising resistance among Staphylococcal isolates, particularly to fluoroquinolones. These findings underscore the importance of region-specific surveillance and antimicrobial stewardship in guiding perioperative prophylaxis in ophthalmology. Vancomycin and aminoglycosides remain effective options, while empirical use of fluoroquinolones warrants cautious re-evaluation.