In vitro Evaluation of antibacterial agents against ocular Bacterial isolates from a Tertiary Hospital, South-West of Nigeria

Abstract

ABSTRACT Failure to cure eye infections and reduced potency in ocular antibacterial agents had been observed in South Western Nigeria, this study sought to evaluate in vitro, the efficacy of antibacterial agents used in the treatment of eye infections. A total of 135 bacterial isolates were recovered from the diagnostic laboratory of the University College Hospital, Ibadan, from conjunctival swabs of patients having underlying eye diseases (Cataracts and glaucoma), and from patients presenting with other symptoms of eye infections (conjunctivitis, keratitis and dacryocystitis). The pathogens incriminated were Staphylococcus aureus (75.5%), Coagulase negative Staphylococci (11.1%), Klebsiella species (11.1%), and Pseudomonas aeruginosa (2.2). Disc diffusion tests (Kirby-Bauer method) were carried out using ciprofloxacin, gentamicin, chloramphenicol, erythromycin, amoxicillinclavulanate, cefuroxime and levofloxacin. Broth dilution technique was thereafter demonstrated using gentamicin, chloramphenicol and ciprofloxacin. The macrolideerythromycin was 54.4% efficacious, amoxicillin-clavulanate and cefuroxime showed 69.9% and 72.8% efficacy. Minimum inhibitory concentrations (MIC) of commonly used antibiotics however showed different levels of resistance. Resistance to the aminoglycosides was marked, yielding 51.6%, with MIC 50 = 8, MIC 90 > 256, resistance to chloramphenicol was also marked, yielding 76.9%, with MIC 50 = 8, MIC 90 = 64. The fluoroquinolones showed high efficacy; levofloxacin and ciprofloxacin showed 91.1% and 75.5% susceptibility respectively, with MIC 50 < 0.5, though slightly demonstrable resistance was observed (MIC 90 = 8). This study recommends discontinuation of empirical therapy by physicians in order to stem the tide of resistance; it justifies the inclusion of the fluoroquinolones in susceptibility testing of bacterial isolates and its first line of choice if cure is warranted