Conjunctival Bacterial Flora And Antibiotic Resistance Patterns After Pre-operative Application Of Topical Levofloxacin 0.3%

Abstract

Purpose: : To evaluate the bacterial flora of the conjunctiva and the antibiotic resistance pattern of conjunctival bacteria in patients undergoing cataract surgery before and after preoperative prophylaxis with topical levofloxacin 0.3%.

Methods: : After IRB approval had been obtained, 237 patients undergoing cataract surgery were recruited for this prospective study at the Department of Ophthalmology, Ludwig-Maximilians University from July to December 2010. All patients received topical levofloxacin 0.3% 4 times daily on the day before surgery and once on the day of surgery into the eye which was scheduled to be operated. Conjunctival specimens were obtained in the operating theater from both the operative eye and the fellow eye, which served as a control. All specimens were inoculated onto blood and chocolate agar plates and into thioglycolate-broth, immediately. Bacteria were isolated, identified and antibiotic susceptibility was tested using the Vitek 2 system. Antibiotic susceptibility testing was done for Streptococci using the Kirby-Bauer method.

Results: : Of the 234 control eyes, 186 (79.5%) had positive cultures. Coagulase negative Staphylococcus (CNS) was found in 161 eyes (68.8%) and was the most frequently isolated organism. One-hundred and forty-nine (62.9%) of 237 eyes receiving topical levofloxacin 0.3% had bacterial growth, of which CNS was found in 111 eyes (46.8%). After the application of topical levofloxacin significantly fewer positive cultures were found (P < 0.0001). There were no significant differences in the resistance patterns of bacteria isolated from treated and control eyes (P = 0.0647). All bacteria were sensitive to linezolid. More than 97% were susceptible to rifampicin, teicoplanin, vancomycin, and imipenem. Between 70-90% were susceptible to oxacillin, ciprofloxacin, levofloxacin, clindamycin and fosfomycin. Less than 70% were susceptible to erythromycin and tetracycline. Only 24% were susceptible to penicillin. In the control eye 37 (19.3%) of the isolated CNS were resistant to more than four antibiotics whereas in the operative eye 15 CNS (14.7%) were resistant to more than four antibiotics (P = 0.3288).

Conclusions: : Coagulase negative Staphylococcus was found to be the most frequent bacterium of the conjunctival flora. In most cases CNS was susceptible to antibiotics commonly used in clinical practice. Only few CNS showed resistance to 4 or more antibiotics.

Keywords: cataract • endophthalmitis • bacterial disease