Elsevier

Ophthalmology

Volume 118, Issue 11, November 2011, Pages 2161-2165
Ophthalmology

Original article
Antibiotic Resistance in Microbial Keratitis: Ten-Year Experience of Corneal Scrapes in the United Kingdom

https://doi.org/10.1016/j.ophtha.2011.04.021Get rights and content

Purpose

To determine the scale of antibiotic resistance in microbial keratitis in East Kent, United Kingdom.

Design

Retrospective, observational case series.

Participants

Corneal scrapes over a 10-year period to December 2008 were identified using the local microbiology database, which provided culture results and antibiotic sensitivity-resistance profiles.

Testing

Isolate sensitivity to chloramphenicol, cefuroxime, gentamicin, and ciprofloxacin was determined by microdilution using the Microscan System (Siemens Diagnostics, Dearfield, IL).

Main Outcome Measures

Isolates were graded as sensitive, intermediate, or resistant to the tested antibiotics, with minimal inhibitory concentrations interpreted against breakpoints from the Clinical and Laboratory Standards Institute.

Results

There were 476 scrapes from 440 patients (female, 57.6%; mean age, 53.5 years). All samples were cultured. Culture was positive in 163 samples (34.2%), growing 172 organisms. Bacterial keratitis accounted for 162 isolates (94.2%), of which 99 (61.1%) were gram-negative. There was a general increase in the number of gram-negative isolates with time (P=0.003). In vitro testing showed widespread gram-negative resistance to chloramphenicol (74.1%), with reducing sensitivity over the study period (P=0.004). There was 97.3% sensitivity to combination gentamicin and cefuroxime, and 94.4% sensitivity to ciprofloxacin. Ciprofloxacin resistance was found in 8 (17.0%) of 47 gram-positive isolates tested, with no trend toward increasing resistance.

Conclusions

This study has documented the highest levels of gram-negative keratitis in any open retrospective survey to date and highlights a trend of increasing gram-negative infection. We have demonstrated reducing chloramphenicol sensitivity, with high sensitivity to combination gentamicin and cefuroxime, as well as ciprofloxacin. Gram-positive fluoroquinolone resistance was higher than previously reported in the United Kingdom, but showed no evidence of increasing resistance. Second-generation fluoroquinolone monotherapy remains the recommended empirical treatment in microbial keratitis in the United Kingdom, and a change to fourth-generation compounds is not advised. Continued testing is essential to monitor for increasing resistance.

Financial Disclosure(s)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Section snippets

Materials and Methods

The East Kent Hospitals University National Health Service Foundation Trust microbiology database was used to identify all corneal scrape samples undertaken from January 1, 1999 to December 31, 2008. Non-corneal samples, such as conjunctival swabs, were excluded. The database was then used to obtain basic patient demographic information and results of microscopy, culture, and subsequent antibiotic sensitivity and resistance testing. The Kent Research Ethics Committee approved the study.

All

Results

During the 10-year period, 476 corneal scrapes were undertaken in 440 patients. Female patients were investigated more than male patients (57.6% vs. 42.4%, P=0.001). The age of patients sampled showed a bimodal distribution, with peaks in the 31–40-year and 81–90-year age groups.

All samples were cultured. Culture was positive in 163 samples (34.2%), growing 172 organisms, with polymicrobial infection in 9 scrapes (5.5%). Bacterial keratitis accounted for 162 positive growths (94.2%), with 5

Discussion

This study has documented the highest levels of gram-negative keratitis in any known retrospective survey to date and highlights a trend of increasing gram-negative infection. We have demonstrated reducing chloramphenicol sensitivity, with high isolate sensitivity to combination gentamicin and cefuroxime, as well as ciprofloxacin. Gram-positive fluoroquinolone resistance was higher than previously reported in the United Kingdom, but showed no evidence of increasing resistance.

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  • Cited by (0)

    Manuscript no. 2010-1152.

    Aspects of data from this study were presented at: the Annual Congress of The Royal College of Ophthalmologists, May 20, 2009, Birmingham, United Kingdom.

    Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

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