Comparison of Bacterial Etiology of Infectious Corneal Ulcers in Contact Lens Wearers and Non-Contact Lens Wearers at the University of Chicago

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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, Krishna Patel1, Michael A.
  Saidel MD1
• 1Division of Ophthalmology and Visual Science,
  University of Chicago, Chicago, IL
• Authors have no financial interests

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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.

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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).

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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

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Results

• 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
  cultures.

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Most common organisms

• Coagulase negative staphylococcus (14/51)
• Psuedomonas aeruginosa (9/51)
• Staphylococcus aureus (9/51)
• a hemolytic streptococci (6/51)
• Corynebacterium (5/51)

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.5 most common organisms in non-contact lens
wearers

• Staphylococcus aureus (9/32)
• a hemolytic streptococci (5/32)
• Coagulase negative staphylococcus (4/32)
• Psuedomonas aeruginosa (4/32)
• 5. Corynebacterium (4/32)

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6 most common organisms in contact lens wearers

• Coagulase negative staphylococcus (10/19)
• Psuedomonas aeruginosa (5/19)
• 3. Moraxella (1/19)
• 4. Serratia (1/19)
• 5. a hemolytic streptococci (1/19)
• 6. Corynebacterium (1/19)

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Conclusion

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

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• 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.

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• 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.

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References

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   Factors influencing predilection and outcome in
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   Comparison of virulence factors in Pseudomonas
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