Extensively Drug-Resistant Pseudomonas aeruginosa Keratitis After Photorefractive Keratectomy Because of Contaminated Eye Drops: Experience With Colistin-Based Therapy

Purpose: This study aims to report the clinico-microbiological characteristics of cases of infectious keratitis caused by extensively drug-resistant Pseudomonas aeruginosa after photorefractive keratectomy (PRK) and to identify the source of infection. Methods: Retrospective review of 7 eyes from 4 patients presenting with infectious keratitis after bilateral PRK performed at different centers and time points, evaluated at a tertiary eye care center in India between March 2024 and August 2025. We analyzed demographic, clinical, microbiological, treatment, and outcome data. Results: The study included 7 eyes from 4 patients. Patients presented, on average, after 2.5 days (range, 1–4 ), and visual acuity ranged from 20/50 to perception of light with inaccurate projection of rays. Corneal infiltrates were central and full-thickness, with severe stromal lysis in 5 of the 7 eyes; 1 eye had a midstromal infiltrate, and 1 eye had pinpoint anterior stromal infiltrates. Hypopyon was present in 6 eyes. In all cases, microbiological examination revealed Gram-negative bacilli, confirmed to be Pseudomonas aeruginosa on culture. The isolate was resistant to all antibiotic classes, with intermediate susceptibility only to colistin. Six of 7 eyes recovered with medical therapy (topical colistin 0.19%) alone, whereas 1 eye underwent therapeutic penetrating keratoplasty (TPK). Source evaluation in all cases revealed identical organisms with similar antimicrobial resistance patterns in the eye drops used and left over by the patient, and in unopened similar drops. Conclusions: This series highlights early recognition of extensively drug-resistant infections after PRK surgery, source identification, and prompt, microbiology-guided therapy, resulting in favorable outcomes.