Susceptibility comparisons of normal preoperative conjunctival bacteria to fluoroquinolones.

Purpose: To compare the susceptibility and efficacy of 3 fluoroquinolones, (levofloxacin, gatifloxacin, and moxifloxacin) in treating conjunctival bacteria in patients having ocular surgery.

Setting: Osaka University Hospital, Osaka, and Tohoku University Hospital, Miyagi, Japan.

Methods: Eyes of patients were examined preoperatively. Aerobic and anaerobic cultures were obtained from conjunctival swabs. The minimum inhibitory concentrations (MICs) of levofloxacin, gatifloxacin, and moxifloxacin for isolated strains were determined. Using the MIC values, descriptive statistics (median, MIC(50), MIC(90), mode, and range), susceptibility, and efficacy of each fluoroquinolone were calculated for the bacteria isolated, and the data were analyzed statistically.

Results: Of the 200 eyes sampled, 163 (81.5%) had positive bacterial growth. From the 163 eyes, 235 bacterial strains were isolated: 116 (49.4%) Propionibacterium acnes; 58 (24.7%) coagulase-negative Staphylococcus (CNS), including 36 methicillin-sensitive CNS (MS-CNS) and 22 methicillin-resistant CNS (MR-CNS); 10 (4.3%) Staphylococcus aureus, including 6 methicillin-sensitive S aureus and 4 methicillin-resistant S aureus (MRSA); and 29 (12.3%) Corynebacterium. Approximately 40% of Staphylococci (22/58 CNS, 37.9%; 4/10 S aureus, 40.0%) were methicillin-resistant. Furthermore, 18 (81.8%) of MR-CNS and all 4 MRSA were fluoroquinolone resistant. The MICs of moxifloxacin and gatifloxacin were statistically significantly lower than those of levofloxacin for CNS and P acnes (P<.05, Kruskal-Wallis test). However, there was no statistically significant difference in the susceptibility patterns of the fluoroquinolones for these strains (P>.05, McNemar test).

Conclusion: Because many methicillin-resistant and fluoroquinolone-resistant strains were isolated from the conjunctiva preoperatively, clinicians should be mindful of endophthalmitis or ocular infections associated with these strains.