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Seasonal, Geographic, and Antimicrobial Resistance Patterns in Microbial Keratitis: 4-Year Experience in Eastern Pennsylvania

Ni, Nina MD; Nam, Enoch M. MD; Hammersmith, Kristin M. MD; Nagra, Parveen K. MD; Azari, Amir A. MD; Leiby, Benjamin E. PhD; Dai, Yang MS; Cabrera, F. Abigail MPH; Ma, Jenny F. BA; Lambert, Calvin E. Jr BA; Honig, Stephanie E. BA; Rapuano, Christopher J. MD

doi: 10.1097/ICO.0000000000000352
Clinical Science

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.

*Wills Eye Hospital, Philadelphia, PA;

Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA;

Loma Linda University School of Medicine, Loma Linda, CA;

§The Warren Alpert Medical School of Brown University, Providence, RI; and

The University of Pennsylvania, Philadelphia, PA.

Reprints: Nina Ni, MD, Wills Eye Hospital, 840 Walnut St, Suite 800, Philadelphia, PA 19107 (e-mail:

Supported by the Wills Eye Innovation Research Grant, Philadelphia, PA.

The authors have no conflicts of interest to disclose.

Received September 14, 2014

Received in revised form November 14, 2014

Accepted November 16, 2014

Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.