Global burden, risk factors, causative organisms and antibiotic susceptibility patterns in bacterial keratitis

This systematic review and meta-analysis aimed to evaluate the global burden, microbial causes, risk factors, and antibiotic susceptibility patterns of bacterial keratitis (BK) among patients with microbiologically confirmed infectious keratitis.

We conducted a systematic search of PubMed, Scopus, Cochrane CENTRAL, and PsycINFO through July 1, 2022. Eligible observational studies reported microbiologically confirmed BK cases and bacterial antibiotic susceptibility. Two reviewers independently screened studies and extracted data. Risk of bias was assessed, and a random-effects meta-analysis was performed to estimate the pooled proportion of BK among all infectious keratitis cases. The protocol was registered in PROSPERO (CRD420251088592). Reported risk factors and antibiotic susceptibility were synthesized descriptively.

From 5180 records screened, 58 studies involving over 134,000 patients were included. The pooled global prevalence of BK was 44 % (95 % CI: 39-49 %) with high heterogeneity (I² ≈ 97 %). Regional variation was notable, ranging from ∼61 % in Oceania to ∼29 % in Africa. Of ∼25,000 bacterial isolates, 72 % were Gram-positive. Dominant species included Staphylococcus epidermidis(15 %), Streptococcus pneumoniae (13 %), Staphylococcus aureus (10 %), and Pseudomonas aeruginosa (17 %). Reported risk factors included trauma (∼44 %) and contact lens wear (∼23 %). Gram-positive isolates showed >95 % susceptibility to vancomycin; Gram-negatives were >90 % susceptible to aminoglycosides and cephalosporins. Fluoroquinolone susceptibility was lower (∼77 % for S. aureus), and ∼20 % of S. aureus were MRSA.

Nearly half of infectious keratitis cases worldwide are bacterial. Findings underscore the need for prevention strategies focused on trauma and contact lens hygiene, and broad empirical therapy targeting MRSA and Pseudomonas.