Trends in resistance to ciprofloxacin, cefazolin, and gentamicin in the treatment of bacterial keratitis

J Ocul Pharmacol Ther. 2008 Apr;24(2):217-23. doi: 10.1089/jop.2007.0085.


Purpose: The aim of this study was to evaluate the microbial profile, resistance patterns, and antibiotic sensitivity of bacterial keratitis to three commonly used ocular antibiotics.

Methods: All cases of bacterial keratitis referred to the Massachusetts Eye and Ear Infirmary Microbiology Laboratory from two consecutive annual 10-month periods were reviewed. The bacterial profile and resistance to ciprofloxacin, cefazolin, and gentamicin was evaluated within the two intervals.

Results: Of the 485 cultures analyzed, 66.4% (322) were positive for bacterial isolates. Of these, 19.2% were polymicrobial, 87.5% were gram-positive, and 12.5% were gram-negative. The most prevalent isolate was coagulase-negative Staphylococcus (45.5%), followed by S. aureus (15.2%). The resistance patterns for gram-positive bacteria for ciprofloxacin for the first versus second time interval were 12% and 22% (P = 0.04) respectively, for cefazolin 13% and 23% (P = 0.04), and for gentamicin 4% and 7% (P = 0.36). The resistance patterns for gram-negative bacteria for ciprofloxacin, cefazolin, and gentamicin were not significantly different in the two tested time periods (all P > 0.05).

Conclusions: There was increased resistance of gram-positive organisms to ciprofloxacin and cefazolin, but not gentamicin, in the two examined time periods. Increased resistance to these commonly used antibiotics emphasizes the need for close follow-up after initial empiric treatment, and maintaining a low threshold for selecting alternative therapy.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Cefazolin / pharmacology
  • Ciprofloxacin / pharmacology
  • Drug Resistance, Bacterial*
  • Eye Infections, Bacterial / drug therapy*
  • Gentamicins / pharmacology
  • Gram-Negative Bacterial Infections / drug therapy
  • Gram-Positive Bacterial Infections / drug therapy
  • Humans
  • In Vitro Techniques
  • Keratitis / drug therapy*
  • Microbial Sensitivity Tests
  • Retrospective Studies


  • Anti-Bacterial Agents
  • Gentamicins
  • Ciprofloxacin
  • Cefazolin