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Clinical resistance of Staphylococcus keratitis to ciprofloxacin monotherapy.

PURPOSE
To review the in vitro susceptibility and the clinical response to 0.3% ciprofloxacin in Staphylococcus aureus keratitis.


METHODS
This is a non-comparative case series derived from a prospectively collected database and analysed retrospectively. One hundred and twenty one patients presenting in the cornea service of LV Prasad Eye Institute, Hyderabad, India, between January 1993 and December 2000, and identified to have S. aureus keratitis were included in the study. All patients had received slitlamp evaluation of the cornea and diagnostic microbiologic workup. They were treated with topical antimicrobial therapy based on smear and culture results. All S. aureus isolates were tested for antibiotic susceptibility by disk diffusion and those resistant to ciprofloxacin were confirmed by testing for minimum inhibitory concentration. The patients' clinical response to the antimicrobial therapy was noted.


RESULTS
Twenty-five (20.6%) of 121 isolates resistant to ciprofloxacin on in vitro susceptibility testing were further analysed in this study. Fifteen of these 25 (60%) patients were initially treated with topical ciprofloxacin. Twelve of 15 (80%) patients showed no clinical improvement (3-8 days). Based on antibiotic susceptibility results, the antibiotic therapy was modified to fortified cefazolin and gentamicin in seven (58.3%), to vancomycin in one and to chloramphenicol in four cases. The corneal infiltrate resolved in 11 (73.3%) of 15 cases. Two patients required penetrating keratoplasty (PK), one required evisceration, and one patient was lost to follow up. Nine of 25 patients were initially started on fortified cefazolin and gentamicin therapy based on smear positive for gram-positive cocci; this resulted in resolution of infiltrate in 44.4% (4/9) while three required change of antibiotics (vancomycin-2, chloramphenicol-1), one required PK and one patient was lost to follow up. One of 25 patients started and continued on chloramphenicol, showed no response and required PK.


CONCLUSIONS
This study shows a significant resistance of S. aureus to many antibiotics including ciprofloxacin and highlights the need for an alternative to ciprofloxacin monotherapy for the treatment of staphylococcal keratitis.