Abstract / Summary
Objectives: Assess bacterial isolate aetiology, antimicrobial (AMR) and multidrug (MDR) resistance trends, cultured from patients with infectious keratitis at a tertiary referral hospital in South India. Methods: This retrospective study examined all-bacterial aetiology, and AMR/MDR profiles of Streptococcus pneumoniae, Nocardia spp., Staphylococcus aureus and Pseudomonas aeruginosa from bacterial keratitis microbiology records (2013-2024). Spearman's rank correlation was used to identify significant trends over the twelve-year period. Results: P. aeruginosa (n=1047) and S. pneumoniae (n=987) were the most frequently isolated species. Significant increases in the number of P. aeruginosa (rs: 0.66; P=0.0219) and S. aureus (rs: 0.70; P=0.0130) cultured isolates were identified. Few (significant) AMR trends emerged across the species, and none with first-line bacterial keratitis treatment drugs. However, the number of AMR and MDR S. aureus isolates increased significantly (rs:0.66; P=0.0235, rs:0.63; P=0.0385, respectively) over time. In total, 64% of methicillin-sensitive S. aureus (MSSA) and 89% of methicillin-resistant S. aureus (MRSA) isolates were resistant to first-line (moxifloxacin) treatment. Conversely, only 2% of S. pneumoniae and 1% of Nocardia spp. isolates were resistant to first-line treatment. Although P. aeruginosa AMR rates increased significantly over time (rs:0.83; P=0.0013), 96% of total isolates remained susceptible to first-line treatment. Conclusion: Bacterial aetiology and antibiotic resistance rates changed over time for several key pathogens causing keratitis, most notably for S. aureus. Dual therapy (moxifloxacin plus cefotaxime) may better address MSSA infections (98% susceptibility), while the high (57%) MDR MRSA rate may necessitate more tailored treatment plans based on isolate susceptibility reports.