Epidemiology, Microbiology, and Outcomes of Culture- Positive Bacterial Keratitis: The Kent Microbial Keratitis Study

Abstract Background Bacterial keratitis (BK) is a significant cause of corneal blindness worldwide. This study presents the first comprehensive analysis of culture-positive BK in Kent. Methods This retrospective observational study analysed culture-positive BK presenting to Maidstone and Tunbridge Wells NHS Trust and East Kent Hospitals University NHS Foundation Trust between January 2020 and December 2024. Clinical data were collected including risk factors, microbiological results, treatment regimens, and outcomes. Poor visual outcome was defined as best-corrected visual acuity < 6/24. Statistical analysis employed univariable and multivariable logistic regression to identify predictors of adverse outcomes. Results A total of 198 patients with culture-positive BK were identified with culture positivity rate of 40.1% and mean age of 58 ± 19.4 years. Predisposing factors were identified in 88.4% of patients, with contact lens (CL)-wear predominating (51.0%), followed by ocular surface disease (OSD; 34.9%) and systemic immunosuppression (28.3%). Gram-negative bacteria predominated (63.6%), with Pseudomonas aeruginosa representing 40.2% of isolates. CL-wear was significantly associated with Pseudomonas aeruginosa (84.2% of CL cases, p = 0.001), whilst OSD, immunosuppression, topical steroid use, and prior corneal surgery were associated with gram-positive infections. Therapeutic keratoplasty was required in 15.2% of patients, with 48.1% achieving poor visual outcomes. Multivariable analysis identified epithelial defect size >3mm as the only independent predictor of poor visual outcomes (OR 3.87, 95% CI 1.68–9.26, p = 0.002). Discussion This study demonstrates evolving epidemiological patterns of BK in Kent, with gram-negative predominance, and CL-wear as the primary modifiable risk factor. Epithelial defect size emerged as the strongest predictor of poor visual outcome.