Antibiotic Susceptibility of Conjunctival Bacterial Isolates from Refractive Surgery Patients

Purpose To determine the in vitro antibiotic susceptibility patterns of conjunctival bacterial flora isolated before surgery from patients undergoing refractive surgery. Design In vitro laboratory investigation. Participants One hundred five eyes from 105 patients scheduled for refractive surgery at Balgensesang Ophthalmology Clinic between September 2005 and January 2006 were studied. Among 105 patients, 71 (67.6%) underwent LASIK using a femtosecond laser, 24 (22.9%) underwent LASIK using an automated microkeratome, 8 (7.6%) underwent LASEK, and 2 (1.9%) patients underwent phakic intraocular lens implantation. Methods Preoperative conjunctival swab samples were inoculated directly in culture media at the bedside before topical anesthetic or antibiotic application. Blood agar, chocolate agar, thioglycolate broth, Sabouraud dextrose agar, and Ogawa media were used for bacterial, fungal, and mycobacterial cultures. Main Outcome Measures Minimum inhibitory concentrations (MICs) of ofloxacin (OFX), levofloxacin (LEV), gatifloxacin (GAT), moxifloxacin (MOX), gemifloxacin (GEM), and other commonly used antibiotics were determined using an E test. Results From 105 patients, 73 (85%) coagulase-negative staphylococci (CNS), 2 (2.3%) Staphylococcus aureus , 1 (1.2%) Streptococcus pneumoniae , and 5 (4.8%) gram-negative bacilli were isolated. No fungi or mycobacteria were isolated. The MIC that would inhibit the growth of 90% of the tested bacterial isolates (MIC90 ) of OFX, LEV, GAT, MOX, and GEM for methicillin-susceptible CNS (n = 46) were 0.5 μg/ml, 0.19 μg/ml, 0.094 μg/ml, 0.047 μg/ml, and 0.023 μg/ml, respectively. The MIC90 values for methicillin-resistant CNS (n = 27) were 32 μg/ml, 4 μg/ml, 1 μg/ml, 0.5 μg/ml, and 0.25 μg/ml, respectively ( P