Seasonal, geographic, and antimicrobial resistance patterns in microbial keratitis: 4-year experience in eastern Pennsylvania

Cornea. 2015 Mar;34(3):296-302. doi: 10.1097/ICO.0000000000000352.

Abstract

Purpose: The aim of this study was to review the demographics, causative organisms, seasonal and geographic variation, and antimicrobial resistance patterns of microbial keratitis at our institution over a 4-year period.

Methods: Electronic medical records of all patients with microbial keratitis who underwent corneal culturing at a single institution in eastern Pennsylvania between January 1, 2009 and December 31, 2012 were reviewed.

Results: A total of 311 patients representing 323 instances of infectious keratitis were analyzed. The most frequently implicated organisms in contact lens-related infections were Pseudomonas aeruginosa for bacteria and Fusarium species for fungus, compared with Staphylococcus aureus and Candida species in non-contact lens-associated bacterial infections. Bacterial keratitis occurred most frequently in spring and least frequently in winter (P = 0.024). Patients who live in large fringe metro (suburban) areas accounted for the highest proportion of infectious keratitis cases. P. aeruginosa and methicillin-sensitive S. aureus isolates were highly susceptible to fluoroquinolones, whereas 32% of coagulase-negative staphylococcus isolates tested were resistant to moxifloxacin and gatifloxacin, and all methicillin-resistant S. aureus organisms tested were resistant to these 2 fluoroquinolones. No organisms tested were resistant to tobramycin, gentamicin, or vancomycin. No fungal infections tested were resistant to voriconazole.

Conclusions: Most infectious keratitis occurred in nonwinter months and in patients from suburban counties. Although fluoroquinolones were effective against the most common bacteria, staphylococcal species exhibited a high rate of resistance, representing a therapeutic challenge given the increasing use of fluoroquinolones as first-line monotherapy. No organisms tested were resistant to tobramycin, gentamicin, vancomycin, or voriconazole.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Anti-Infective Agents / pharmacology
  • Anti-Infective Agents / therapeutic use*
  • Corneal Ulcer / drug therapy
  • Corneal Ulcer / epidemiology
  • Corneal Ulcer / microbiology*
  • Drug Resistance, Multiple, Bacterial*
  • Drug Resistance, Multiple, Fungal*
  • Eye Infections, Bacterial / drug therapy
  • Eye Infections, Bacterial / epidemiology
  • Eye Infections, Bacterial / microbiology*
  • Eye Infections, Fungal / drug therapy
  • Eye Infections, Fungal / epidemiology
  • Eye Infections, Fungal / microbiology*
  • Female
  • Fluoroquinolones / pharmacology
  • Humans
  • Male
  • Microbial Sensitivity Tests
  • Middle Aged
  • Pennsylvania / epidemiology
  • Regression Analysis
  • Seasons

Substances

  • Anti-Infective Agents
  • Fluoroquinolones