INTRODUCTION: This study aimed to determine the in vitro susceptibility of standard isolates of common pathogens causing bacterial conjunctivitis to non-fluoroquinolone antimicrobial ophthalmic medications. METHODS: This is a single-blind experimental study which compared the in vitro susceptibility of Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa and Staphylococcus epidermidis to locally available non-fluoroquinolone ophthalmic medications, specifically chloramphenicol, tobramycin, fusidic acid, gentamicin sulfate, sulfacetamide and polymyxin-neomycin. Utilizing the disk diffusion method, zones of inhibition in millimeters for each bacterial isolate was recorded and tabulated. Kruskal-Wallis test was used to determine statistical differences. RESULTS: Both Staphylococci were sensitive to all antibiotics except sulfacetamide. Only chloramphenicol showed activity against all four isolates. Tobramycin showed the largest zone of inhibition against Pseudomonas aeruginosa. There was statistically significant difference in the median zone of inhibition in each antimicrobial medication against Staphylococcus aureus (p = 0.002) and Staphylococcus epidermidis (p < 0.001) with the largest mean zone of inhibition by fusidic acid of 34 and 38 millimeters, respectively. Streptococcus pneumoniae was least susceptible to antibiotics tested; only chloramphenicol and fusidic acid showed activity. There were also significant differences in the median zones of inhibition across the isolates. CONCLUSION The standard isolates are susceptible to at least one non-fluoroquinolone ophthalmic medication. The antibiotics tested showed differences in activity against the four isolates. The findings of this study may be used as a basis to review local practice patterns or/and initiate revisions in the guidelines for prescribing initial treatment of bacterial conjunctivitis.
Conjunctivitis, Bacterial ; Anti-Bacterial Agents