Fifteen-Year Review of Corneal Scrape Bacterial Microbiology and Antibiotic Susceptibility from the Canberra Health Services

Background: This retrospective study evaluated bacterial growth and antibiotic susceptibility profiles of corneal scrapes collected for suspected microbial keratitis at Canberra Health Services between 2010 and 2025, providing the first longitudinal analysis from a regional Australian tertiary care center. Materials and Methods: Corneal scrape results from adult patients (>18 years) were retrospectively reviewed. Collected data included demographics, clinical risk factors, bacterial isolates, and antibiotic susceptibility. Categorical comparisons between two 7.5-year periods were performed using Fisher’s exact or chi-squared tests ( P ≤ 0.05). Results: Of 430 corneal scrapes, 227 (53%) yielded positive cultures, with 135 (151 isolates) that underwent susceptibility testing and were analyzed in this study. The mean age was 60 years (range: 18–96 years), with 54% female and 19% from rural or regional areas. Common risk factors included contact lens wear (20%), trauma (15%), and ocular surface disease (31%). Predominant isolates were coagulase-negative Staphylococcus spp. (29%), Staphylococcus aureus (23%), and Pseudomonas aeruginosa (16%). No statistically significant change in antibiotic susceptibility was observed for chloramphenicol, cefazolin, vancomycin, fluoroquinolones, or aminoglycosides when comparing the first and second 7.5-year intervals. S. aureus and Streptococcus species remained fully susceptible to all tested agents. Coagulase-negative Staphylococcus demonstrated reduced susceptibility to cefazolin (79%) but maintained high susceptibility (≥92%) to all other antibiotics. Pseudomonas species showed limited susceptibility to chloramphenicol (22%) but remained susceptible to fluoroquinolones and aminoglycosides. Conclusion: Over 15 years, a minimal change in the bacterial profile and no change in antimicrobial susceptibility to standard antibiotics was observed, consistent with the observations of national literature and supporting current empirical treatment protocols.