1. Comparison of Bacterial Etiology of Infectious Corneal Ulcers in Contact Lens Wearers and Non-Contact Lens Wearers at the University of Chicago Shuchi B. Patel MD 1, Krishna Patel 1, Michael A. Saidel MD 1 1 Division of Ophthalmology and Visual Science, University of Chicago, Chicago, IL Authors have no financial interests

2. Purpose We analyzed the laboratory results of corneal ulcers seen at University of Chicago between 2002 and 2007 in order to determine the relative frequencies of pathogens causing bacterial ulcers in both contact lens related and non-contact lens related. The results were then divided into two subgroups (contact lens associated, and non- contact lens associated). The bacterial spectrum was compared as well as the antibiotic susceptibilities.

3. Methods A retrospective chart review was done for all patients identified as having a corneal ulcer between the years 2002 and 2007. Only patients with central corneal ulcers were included in the study. Patients with viral, fungal, protozoan or neurotrophic ulcers were excluded (eg. bacterial ulcers only).

4. Cultures Technique – Taken with Kimura spatula – With or without anesthesia – Streaked on blood, chocolate, and Sabourad dextrose agar Lowenstien-Jensen, thioglycolate, nonnutrient agar with E. Coli overlay used if appropriate – Sent for Gram and Giemsa stain – Considered a positive culture If at least one colony was seen on two or more media Or if a colony was present on a single medium and the organism was also identified on staining

5. Results 251 charts were reviewed. 251 charts were reviewed. 62 central corneal ulcers were identified. 62 central corneal ulcers were identified. – 53 of these ulcers were cultured (85%). – 34 of the cultured ulcers had positive cultures (64%). – 29 patients were contact lens wearers (47%). Many of the ulcers were polymicrobial, with a total of 51 organisms isolated from the 34 cultures. Many of the ulcers were polymicrobial, with a total of 51 organisms isolated from the 34 cultures.

6. Most common organisms 1.Coagulase negative staphylococcus (14/51) 2.Psuedomonas aeruginosa (9/51) 3.Staphylococcus aureus (9/51)  hemolytic streptococci (6/51) 5.Corynebacterium (5/51)

7. . 5 most common organisms in non- contact lens wearers 1.Staphylococcus aureus (9/32)  hemolytic streptococci (5/32) 3.Coagulase negative staphylococcus (4/32) 4.Psuedomonas aeruginosa (4/32) 5. Corynebacterium (4/32)

8. 6 most common organisms in contact lens wearers 1.Coagulase negative staphylococcus (10/19) 2.Psuedomonas aeruginosa (5/19) 3. Moraxella (1/19) 4. Serratia (1/19) 5.  hemolytic streptococci (1/19) 6. Corynebacterium (1/19)

9. Conclusion The antibiotic susceptibilities of the pathogens were similar whether the patient had a contact lens related ulcer or not.

10. There is a different spectrum of bacteria found in ulcers that are found in contact lens wearers versus those in non contact lens wearers, though the antibiotic susceptibilities are similar. The overall bacterial spectrum found was similar in percentages to those from previous publications. – However, in the subgroup analysis, the spectrum appears much different, with Staph aureus becoming the most common agent found. Also, contrary to previously published literature, the most common contact lens associated bacteria was not Psuedomonas aeruginosa but coagulase negative staph.

11. Further studies should be done to determine whether this finding is a new trend, location specific, or due to confounding factors such as previous treatment with antibiotics prior to performance of a culture.

12. References 1.Liesegang TJ, Forster RK. Spectrum of microbial keratitis in South Florida. Am J Ophthalmol. 1980;90:38–47. 2.Jones DB. Initial therapy of suspected microbial corneal ulcers: specific antibiotic therapy based on corneal smears. Surv Ophthalmol. 1979;24:97–116. 3.Gudmundsson OG, Ormerod LD, Kenyon KR, et al. Factors influencing predilection and outcome in bacterial keratitis. Cornea. 1989;8:115–121. 4.Choy MH, Stapleton F, Willcox MD et al. Comparison of virulence factors in Pseudomonas aeruginosa strains isolated from contact lens- and non-contact lens-related keratitis. J Med Microbiol. 2008 Dec;57(Pt 12):1539-46.