Bacterial keratitis in patients with corneal lesions in southeastern Iran: microbial spectrum, demographic characteristics, and seasonal distribution

Background and objective Bacterial keratitis is a sight-threatening ophthalmic emergency that can rapidly progress to corneal ulceration, perforation, endophthalmitis, and permanent blindness if inappropriately managed. Despite its clinical significance, there is a paucity of comprehensive regional microbiological surveillance data regarding the microbial etiology of bacterial keratitis in southeastern Iran. Therefore, this study aimed to provide an updated regional microbiological surveillance report, detailing the bacterial profile, seasonal distribution, and demographic patterns of bacterial keratitis in patients presenting with corneal lesions in this area. Materials and methods This retrospective, descriptive cross-sectional study was conducted between 2020 and 2025. Data were retrieved from the medical registries of tertiary teaching hospitals affiliated with Zahedan University of Medical Sciences. Demographic variables (age, sex), seasonal onset, and microbiological isolates were extracted using standardized checklists. Patients with incomplete clinical or laboratory records were excluded. As a descriptive surveillance study, data were analyzed to establish local epidemiological baselines and pathogen distributions. Statistical analysis was performed using SPSS version 26. Results A total of 358 patients were evaluated, comprising 217 males (60.6%) and 141 females (39.4%). While bacterial isolates showed numerical variations across seasons (higher in Spring/Summer: 52.0% vs. Autumn/Winter: 48.0%) and genders (males: 60.6%), these demographic and seasonal distributions were not statistically significant (p > 0.05p > 0.05). The five most prevalent bacterial isolates were Staphylococcus epidermidis (n = 126, 35.2%), Staphylococcus saprophyticus (n = 59, 16.5%), Streptococcus pneumoniae (n = 50, 14.0%), Pseudomonas spp. (n = 37, 10.3%), and Acinetobacter spp. (n = 23, 6.4%). Regarding age distribution, S. epidermidis was most frequent in patients aged ≤ 20 years (n = 40) and ≥ 61 years (n = 37), whereas S. saprophyticus peaked in the ≤ 20 years age group (n = 27). Furthermore, Streptococcus pneumoniae (n = 23), Pseudomonas spp. (n = 15), and Acinetobacter spp. (n = 10) showed higher frequencies in older adults aged ≥ 61 years. Temporally, peak numerical frequencies of S. epidermidis, S. saprophyticus, and Acinetobacter spp. occurred in summer, while S. pneumoniae and Pseudomonas spp. peaked in autumn. All major isolates exhibited a higher numerical frequency in male patients. Conclusion Bacterial keratitis in southeastern Iran is characterized by a predominance of Gram-positive cocci, with Staphylococcus epidermidis being the most common isolate. Although numerical variations across seasons and genders were observed, they lacked statistical significance. Consequently, empirical therapy and clinical management should remain consistent throughout the year. Based on the observed microbial spectrum, broad-spectrum empirical therapy targeting both Gram-positive and Gram-negative pathogens should be initiated promptly to optimize clinical outcomes and mitigate visual loss.