Global Burden, Risk Factors, Causative Organisms and Antibiotic Susceptibility Patterns in Bacterial Keratitis
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Background
Bacterial keratitis (BK) is a leading cause of corneal ulceration and vision loss worldwide. We aimed to synthesize global data on BK prevalence, risk factors, causative pathogens, and antibiotic susceptibility through a systematic review and meta-analysis.
Methods
This review (PROSPERO CRD420251088592) searched PubMed, Scopus, Cochrane CENTRAL, and PsycINFO through July 1, 2022, for observational studies of microbiologically confirmed infectious keratitis. Eligible studies reported numbers of BK cases and bacterial antibiotic susceptibility. Two reviewers screened studies and extracted data. The primary outcome was the pooled proportion of keratitis cases attributable to bacteria (random-effects meta-analysis); reported risk factors and susceptibilities were summarized descriptively.
Results
Of 5,180 records screened, 58 studies (>127,000 patients) met inclusion criteria. The pooled BK prevalence was 44% (95% CI 39–49%) with high heterogeneity (I²≈97%); prevalence varied by region (e.g. ∼61% in Oceania vs ∼29% in Africa). Among ∼25,000 bacterial isolates, 72% were Gram-positive. The most common species were Staphylococcus epidermidis (∼15%), Streptococcus pneumoniae (∼13%), Staphylococcus aureus (∼10%), and Pseudomonas aeruginosa (∼17%). Reported predisposing factors included trauma (∼44% of cases) and contact lens wear (∼23%). Gram-positive bacteria were >95% susceptible to vancomycin; Gram-negatives were >90% susceptible to aminoglycosides and cephalosporins. Fluoroquinolone susceptibility was lower (e.g. ciprofloxacin ∼77% for S. aureus ); about 20% of S. aureus isolates were MRSA.
Conclusions
Approximately half of infectious keratitis cases worldwide are bacterial, though the burden varies by setting. The findings emphasize trauma and lens hygiene as key targets for prevention. The predominance of a few organisms and rising resistance patterns underscores the need for broad empirical therapy (covering MRSA and Pseudomonas ). Strengths include the large multinational dataset; limitations include high between-study heterogeneity and sparse data from some regions. These results can inform clinical management and BK prevention strategies.
Funding
No funding was received for this study.
Research in context
Evidence before this study
We searched PubMed/MEDLINE, Scopus, Cochrane CENTRAL, and APA PsycINFO from January 1, 1975, to July 1, 2022, using combinations of the terms “infectious keratitis,” “microbial keratitis,” “corneal ulcer,” and “bacterial keratitis.” We screened titles, abstracts, and full-text articles for studies reporting microbiologically confirmed cases of microbial keratitis with extractable data on bacterial etiology or antibiotic susceptibility. Only English-language human studies were included; case reports, animal studies, and editorials were excluded. Additional studies were identified by manually reviewing reference lists from eligible articles and relevant reviews. Risk of bias was assessed using an adapted GRADE scoring system for prevalence studies. Prior to this study, most available evidence came from single-center studies or regional case series, and there was no comprehensive global synthesis of the prevalence, microbiological profiles, or antimicrobial resistance patterns in bacterial keratitis. No prior systematic review has quantified the global pooled prevalence of bacterial keratitis across multiple continents or assessed the variation in risk factors and susceptibility patterns.
Added value of this study
This is the first global systematic review and meta-analysis to synthesize data on the prevalence, risk factors, causative organisms, and antibiotic susceptibility profiles of bacterial keratitis. We analyzed over 127,000 cases of microbial keratitis from 58 studies across 32 countries, including more than 25,000 bacterial isolates and 5,000 antimicrobial susceptibility profiles. Our findings provide reliable pooled estimates of bacterial keratitis prevalence globally (44%), delineate dominant bacterial species (such as S. epidermidis , P. aeruginosa , S. pneumoniae ), and identify leading modifiable risk factors (such as trauma, contact lens wear). We also report concerning trends in antimicrobial resistance, including rising methicillin resistance and declining fluoroquinolone susceptibility.
Implications of all the available evidence
These findings highlight bacterial keratitis as a global public health concern, particularly in regions with high trauma or contact lens use. The wide variability in prevalence and species distribution underscores the need for regionally tailored prevention and treatment strategies. The declining efficacy of fluoroquinolones and increasing multidrug resistance among ocular pathogens call for urgent attention to antimicrobial stewardship and the development of updated, evidence-based empirical treatment protocols. Our results emphasize the importance of strengthening global surveillance efforts and enhancing microbiological diagnostic capacity, especially in under-resourced settings.
