Bacteria commonly isolated from keratitis specimens retain antibiotic susceptibility to fluoroquinolones and gentamicin plus cephalothin

Abstract

Purpose: Patients presenting with presumed infective keratitis were studied to determine predisposing factors, the current susceptibilities of the bacterial isolates to a range of relevant antibiotics, the success rate of topical antibiotic treatment of keratitis and predictors of failure of topical therapy. Methods: Corneal scrapings taken from patients who presented between January 2002 and December 2003 to the Sydney Eye Hospital Emergency Department with keratitis were cultured. The minimum inhibitory concentration of selected antibiotics was determined for each bacterial isolate using an agar dilution technique. Results: One hundred and twelve consecutive patients presented with corneal ulcers. Forty-seven of the 112 (42%) patients had a growth from the corneal scraping. Potential predisposing factors were identified in 64% of patients, most frequently contact lens wear (36% of patients). Coagulase-negative staphylococci were the most common species isolated. Other common organisms isolated include Pseudomonas aeruginosa, Corynebacterium spp., Staphylococcus aureus and Streptococcus spp. Conclusions: Most microorganisms isolated from patients with bacterial keratitis showed susceptibility to ciprofloxacin and aminoglycosides. Cephalothin plus aminoglycoside constituted an effective initial broad-spectrum antibiotic combination. The success rate of topical antibiotic treatment of corneal abscess is 89%. Predictors of failure include older age group, medium or large ulcer, culture-negative keratitis, hypopyon and poor visual acuity.