Microbiologic patterns and antibiotic sensitivity in microbial keratitis

Purpose: To describe causative pathogens involved in microbial keratitis and trends of microbial isolates sensitivity and resistance to routinely used ophthalmic antibiotics.Methods: This is a retrospective study on smear and culture samples of corneal ulcers in patients who came to Farabi eye hospital emergency ward from January 2012 to December 2018. Results: 8912 samples were collected from patients with keratitis for 6 years, the mean age of patients with keratitis was 44.52±27.46. In patients with keratitis, 60% of cultures were negative. Pseudomonas and S.pneumonia and S.epidermidis were the most common isolates in keratitis( accounting for 10%, 5% and 4% respectively). Among patients younger than 19 years with keratitis, 41.5% were culture negative, and S.viridans was the most common isolate (13.2%) followed by S.aureus (9.5%) and S.pneumonie (8.1%). In the age group of 19-50 years, 54.3% were culture negative and Pseudomonas was the most common microorganism (15%) followed by enterobacter (7.8%) and S.epidermidis and S.aureus (4.3%). And in patients older than 50 years, 65.5% were culture negative, S.pneumonia accounted for 7.8% of isolates and pseudomonas and S.epidermidis for 6.5% and 4.8% respectively. In our study resistance of S.pneumonia to ceftazidim siginificantly increased after 2014 however other changes in antibiotic susceptibility profile was not significant. Conclusion: Pseudomonas and S.pneumonia and S.epidermidis were the most prevalent isolates in keratitis respectively. According to age S.viridans was the most prevalent isolate in patients younger than 19 years old with a rising trend after 2014 and Pseudomonas was the most common isolate in patients with keratitis between 19 to 50 years of age with a decreasing trend in incidence during recent years, but S.pneumonia was responsible formost of culture positive keratitis over 50 years with a decreasing trend in incidence recently.