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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, Krishna1 Patel1,
Michael A. Saidel MD
of Ophthalmology and Visual Science,
University of Chicago, Chicago, IL
Authors have no financial interests
• 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 noncontact lens associated). The bacterial
spectrum was compared as well as the
antibiotic susceptibilities.
• 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).
• 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
– 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
• 251 charts were reviewed.
• 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
Most common organisms
1. Coagulase negative
staphylococcus (14/51)
2. Psuedomonas
aeruginosa (9/51)
3. Staphylococcus aureus
4. a hemolytic streptococci
5. Corynebacterium (5/51)
Top 5 bacteria found in ulcers
Coag negative
Staph aureus
Alpha hemolytic
5 most common organisms in noncontact lens wearers
1. Staphylococcus aureus
2. a hemolytic
streptococci (5/32)
3. Coagulase negative
staphylococcus (4/32)
4. Psuedomonas
aeruginosa (4/32)
5. Corynebacterium
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. a hemolytic
streptococci (1/19)
6. Corynebacterium
• 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
– 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.
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.