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 MD1, Krishna Patel1, Michael A. Saidel MD1

1Division of Ophthalmology and Visual Science, University of Chicago, Chicago, IL

Authors have no financial interests

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.

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).

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

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%). 53 of these ulcers were cultured (85%). – 34 of the cultured ulcers had positive cultures (64%). 34 of the cultured ulcers had positive cultures (64%). – 29 patients were contact lens wearers (47%).29 patients were contact lens wearers (47%).

• Many of the ulcers were polymicrobial, with a Many of the ulcers were polymicrobial, with a total of 51 organisms isolated from the 34 total of 51 organisms isolated from the 34 cultures. cultures.

Most common organisms

1.1. Coagulase negative Coagulase negative staphylococcus (14/51)staphylococcus (14/51)

2.2. Psuedomonas Psuedomonas aeruginosa (9/51)aeruginosa (9/51)

3.3. Staphylococcus aureus Staphylococcus aureus (9/51)(9/51)

4.4. hemolytic streptococci hemolytic streptococci (6/51)(6/51)

5.5. Corynebacterium (5/51)Corynebacterium (5/51)

Top 5 bacteria found in ulcers

Coag negative staph

Psuedomonas

Staph aureus

Alpha hemolytic strep

Corynebacterium

.

5 most common organisms in non-contact lens wearers

1.1. Staphylococcus aureus Staphylococcus aureus (9/32)(9/32)

2.2. hemolytic hemolytic streptococci (5/32)streptococci (5/32)

3.3. Coagulase negative Coagulase negative staphylococcus (4/32)staphylococcus (4/32)

4.4. Psuedomonas Psuedomonas aeruginosa (4/32)aeruginosa (4/32)

5. Corynebacterium 5. Corynebacterium (4/32)(4/32)

6 most common organisms in contact lens wearers

1.1. Coagulase negative Coagulase negative staphylococcus (10/19)staphylococcus (10/19)

2.2. Psuedomonas Psuedomonas aeruginosa (5/19)aeruginosa (5/19)

3. Moraxella (1/19)4. Serratia (1/19)5. 5. hemolytic streptococci hemolytic streptococci

(1/19)(1/19)6. Corynebacterium (1/19)6. Corynebacterium (1/19)

Conclusion

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

• 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.

• 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.

References1. 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.