In vitro susceptibility to different topical ophthalmic antibiotics of bacterial isolates from patients with conjunctivitis.

PURPOSE: To test in vitro the susceptibility to different commercially-available topical antibiotics of isolates from patients with conjunctivitis, evaluated at the Microbiology Service of Turin Ophthalmic Hospital between January 2005-February 2007. METHODS: Bacterial isolates were cultured using both liquid and solid media. The four most frequent isolates were analyzed and their in vitro susceptibility to levofloxacin, ofloxacin, norfloxacin, lomefloxacin, tobramycin, netilmycin, ampicillin, and chloramphenicol was tested, using the Kirby-Bauer diffusion method and National Committee for Clinical Laboratory Standards (NCCLS) serum standards. RESULTS: The four most common bacteria isolates were: Staphylococcus aureus (27%), viridians Streptococci (22%), Staphylococcus epidermidis (16%) and Streptococcus pneumoniae (13%). The in vitro susceptibility to levofloxacin was highest (p<0.01) for all bacterial isolates. CONCLUSIONS: In vitro susceptibility tests showed that levofloxacin had the highest cumulative efficacy against bacterial isolates. Netilmycin showed the highest efficacy against staphylococcus aureus, the most common bacterial isolate in this study.