In vitro antibiotic susceptibility patterns of bacterial keratitis isolates in Oxford, UK: A 10-year review

Abstract

PurposeTo analyse the spectrum of bacterial keratitis isolates and their in vitroantibiotic susceptibilities over a 10-year period in Oxford, UK; and to compare the in vitroefficacy of ciprofloxacin with that of the combination of gentamicin and cefuroxime over the same period.MethodsAll culture-positive corneal scrapes received from the Oxford Eye Hospital between July 1999 and June 2009 were identified retrospectively using a local microbiology database. For analysis of trends over time, the data was split into two equal 5-year periods. Statistical analysis was done using the 2 and Fisher exact tests.ResultsOver the 10-year study period, 467 corneal scrapes were performed of which 252 (54.0%) had positive bacterial cultures, growing a total of 267 organisms. The most commonly isolated bacteria were Staphylococci(40.1%) followed by Pseudomonasspecies (28.5%), other Gram-negative species (17.2%), Streptococci(7.1%), and Corynebacteria(6.0%). Between the first and second time periods there was an increase in the number of coagulase-negative Staphylococciand an increased resistance of the non-Pseudomonas Gram-negative group to chloramphenicol. Of the 189 isolates tested for sensitivity to both empirical antibiotic regimens, 176 (93.2%) were susceptible to ciprofloxacin whereas 188 (99.5%) were susceptible to either gentamicin or cefuroxime (P0.0015).ConclusionsThe spectrum of bacterial keratitis isolates and their in vitroantibiotic sensitivity patterns have generally remained stable over time. The combination of gentamicin and cefuroxime provides a broader spectrum of antimicrobial cover than ciprofloxacin monotherapy in Oxford, although both regimens continue to be appropriate choices for the initial management of this condition. © 2011 Macmillan Publishers Limited All rights reserved.