Abstract
Purpose::
To determine the rate of positive cultures (i.e., with identifiable microbial agent) from corneal scrapings done for suspected microbial keratitis in a North-East Scotland population between 2000-2005, and to describe the associated clinical features.
Methods::
All patients undergoing corneal scrapes for suspected microbial keratitis between 2000-2005 were identified from the database of the Department of Microbiology at Aberdeen Royal Infirmary, Scotland, UK. The medical records of patients with culture positive isolation of microorganisms were reviewed.
Results::
There were 339 corneal scrapes performed between 2000 to 2005. There has been a steady rise in corneal scrapes performed over the six years. In year 2000, 47 corneal scrapes were performed while by year 2005 this has risen to 87 corneal scrapes. Data revealed an increase in culture negative results compared to culture positive isolates, which have not increased (mean average 10.8 cases per year). A total of 65 patients (19%) had a positive culture. Data was available from 43 of them (66.1%). The most commonly identified risk factors for culture positive isolation were surface eye disease (28%), contact lens wear (21%) and Herpes Simplex Keratitis (16%). There has been an increase of contact lens related culture positive ulcers from 12.5% in 2002 to 55% in 2005. Among the culture positive isolates 16% were pretreated with topical antibiotic therapy. Majority (95%) of ulcers had a largest linear dimension of 2mm or more. The most common identified organism was Coagulase negative Staphylococcus (23%) followed by Pseudomonas (21%) and Staphylococcus Aureus (21%).
Conclusions::
The number of corneal scrapes performed for suspected microbial keratitis has increased in our hospital, although the culture positive isolation from these scrapes has remained unchanged. There was a low frequency of culture positive scrapes. The most common organisms identified in this population are not dissimilar to other series published in the literature. An increase in cases associated with contact lens wear has been observed.
Keywords: cornea: epithelium • keratitis • microbial pathogenesis: clinical studies