Ocular Pathogens and Antibiotic Sensitivity in Bacterial Keratitis Isolates at King Khaled Eye Specialist Hospital, 2011 to 2014

Abstract

Background: To investigate prevalence and in vitro susceptibility trends of bacteria isolated from patients with bacterial keratitis from 2011 to 2014 in a tertiary care eye hospital in Saudi Arabia.

Methods: Retrospective review of bacterial isolates from corneal scraping of eyes with microbial keratitis. The most common isolates and their antibiotic resistance profiles were identified; trend analysis was performed over the study period.

Results: A total of 2037 bacterial isolates met inclusion criteria during the study period. Gram positives accounted for 91.4% of isolates, including Staphylococcus epidermidis 962 (27.4%), other coagulase-negative staphylococci 289 (8.2%), Staphylococcus aureus 237 (6.8%), and Streptococcus pneumoniae 159 (4.5%). Pseudomonas aeruginosa was the most common gram-negative isolate (38.4%). All tested Gram positive isolates were sensitive to vancomycin. As a whole, isolates were most sensitive to moxifloxacin and ciprofloxacin with resistance of 3.7% and 3.3%, respectively. Oxacillin resistance was increasingly found in S. aureus (14.8% in 2011, 27.8% in 2014, P = 0.06), but was without significant change in S. epidermidis and other coagulase-negative Staphylococci (range 19.4%-32.0%). There was an increase in moxifloxacin resistance among S. epidermidis, increasing from 0.9% to 12.7%. Using a logistic regression model, the overall change in resistance of bacteria to antibiotics by year was not significant.

Conclusions: Gram-positive bacteria represented the majority of bacteria isolated, with a possibly increasing prevalence of oxacillin resistance in S. aureus. Fluoroquinolone resistance is uncommon, and no vancomycin-resistant gram-positive strains were identified. There was no overall significant trend in antibiotics resistance; however, future surveillance studies are recommended.