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Microbial keratitis: 5 year trends in west London

Session Details

Session Title: Cornea

Session Date/Time: Sunday 16/02/2014 | 08:30-11:00

Paper Time: 09:15

Venue: Linhart Hall (Level -2)

First Author: : YusrahShweikh UK

Co Author(s): :    Lucia Pelosini   Annette Jepson   Melanie Corbett        

Abstract Details


To investigate the spectrum of organisms causing microbial keratitis managed in a tertiary eye hospital in West London. To analyse trends in the incidence of microbial isolates over time. The prevalence of in vitro antibiotic resistance was also determined.


Western Eye Hospital, Imperial Healthcare NHS Trust, London, UK


The Imperial Trust microbiology database was searched retrospectively for all corneal scrape samples received between January 2007 and July 2012. Statistical analyses were performed using SPSS Inc. V 21.0. For the purposes of trend analysis, the time period of study was split into two to enable comparisons between the January 2007-January 2010 and the February 2010-July 2012 groups. Fisher’s exact tests and χ2 tests were performed to examine trends in the incidence of microbial isolates over time.


1860 corneal scrape samples were received of which 387 (20.8%) were culture-positive, yielding a total of 45 different organisms. Pseudomonas species were most commonly isolated (41.6%), followed by coagulase-negative Staphylococci (13.7%), Staphylococcus aureus (8.3%) and alpha-haemolytic Streptococci (3.6%). Fusarium species were cultured in 4 cases, with fungal elements identified in a further 5. The incidence of fungal keratitis was stable over the 5-year study period (P = 1.0). Resistance to tetracycline was most commonly observed (22.8%), followed by penicillin-resistance (20.2%). Ciprofloxacin-resistance was encountered in 4.1% of cases. A further 4.1% of organisms were resistant to ceftazidime and 2.1% were resistant to gentamicin.


The spectrum of organisms causing microbial keratitis in West London has remained largely stable over the last 5 years. Fungal keratitis was diagnosed in 9 cases in our study producing an annualised incidence of 0.48%; a figure much greater than the minimum average incidence of 0.32 cases/million quoted by the British Ophthalmologic Surveillance Unit [1]. The low rate of resistance to third-generation fluoroquinolones and ceftazidime (4.1% respectively) suggests that a combination of these agents remains an appropriate first-line treatment regime with an overall susceptibility of 91.8% in our study population. A high index of clinical suspicion for fungal keratitis should be maintained in those cases responding poorly to empirical antibiotic treatment. The frequency of these rare fungal infections appears to be greater in our inner-city population compared to the nationally reported rates. Further investigation is warranted to establish and explain this trend. FINANCIAL INTEREST: NONE