Prospective randomized study determining whether a 3-day application of ofloxacin results in the selection of fluoroquinolone-resistant coagulase-negative Staphylococcus.

PURPOSE To determine whether a 3-day application of ofloxacin results in the selection of fluoroquinolone-resistant conjunctival coagulase-negative Staphylococcus. DESIGN Prospective randomized trial. METHODS Patients scheduled for ocular surgery were randomized to a control (89 eyes) or study group (70 eyes). The study group received topical ofloxacin (0.3%) four times a day for 3 days. Conjunctival cultures were obtained at baseline (T0) and after 3 days of ofloxacin (T1). Cultures were also obtained at T0 and T1 for the control group, but these eyes did not receive an antibiotic. Bacteria isolated were identified and antibiotic susceptibility was determined. RESULTS At T0, 53 out of 89 patients (60%) in the control and 48 out of 70 patients (69%) in the study group harbored coagulase-negative Staphylococcus. Among these coagulase-negative Staphylococcus, 12 out of 53 in the control and 11 out of 48 in the study group were resistant to ofloxacin (p>0.9999). At T1, significantly fewer coagulase-negative Staphylococcus (p=0.0003) were isolated from the study group (18 coagulase-negative Staphylococcus), compared the control group (48 coagulase-negative Staphylococcus). Of these, 5 out of 17 coagulase-negative Staphylococcus in the study group and 9 out of 48 coagulase-negative Staphylococcus in the control group were resistant to ofloxacin (p=0.5649). There was no significant difference in the number of coagulase-negative Staphylococcus resistant to ciprofloxacin or norfloxacin in the study group compared to the control group at T1. CONCLUSIONS Ofloxacin given four times a day for 3 days does not select out for conjunctival fluoroquinolone-resistant coagulase-negative Staphylococcus.