Fourth-generation fluoroquinolone-resistant bacterial keratitis

Corneal scrapings were collected from a case of keratitis and microbiological investigations done. Coagulase-negative Staphylococcus (Staphylococcus epidermidis) was identified on culture, and antibiotic susceptibility tests were performed. Treatment was started with topical cefazolin sulfate 5% and gatifloxacin 0.3%; this was subsequently changed to vancomycin 5% and tobramycin sulfate 1.3% based on the sensitivity pattern. The isolates of this bacterium were susceptible to vancomycin, tobramycin, and gentamicin, and resistance was present against moxifloxacin, gatifloxacin, ciprofloxacin, and cefazolin. The case highlights the occurrence of keratitis caused by coagulase-negative Staphylococcus that is resistant to treatment with moxifloxacin.