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C. C. Lin, P. Lalitha, M. Srinivasan, N. V. Prajna, T. C. Porco, C. Oldenburg, S. D. McLeod, N. R. Acharya, T. M. Lietman; Seasonal Fluctuations in Fungal and Bacterial Keratitis in South India. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1308.
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Previous studies suggest that fungal keratitis is more common in hot, humid climates while bacterial keratitis is independent of seasonal variation. As empiric therapy is often initiated before culture results return, knowledge of seasonal trends in keratitis has important implications for public health efforts such as screening campaigns. This study analyzes seasonal trends in the incidence of fungal and bacterial keratitis at the Aravind Eye Hospital in South India, a major tertiary referral center.
A retrospective analysis of microbiology database records from a three-year period between August 2006 and July 2009 was performed. A diagnosis of infectious keratitis with a culture and/or smear performed was required for inclusion. Repeat samples from the same patient were excluded. All organisms from polymicrobial cultures were recorded. Time patterns in fungal and bacterial keratitis were analyzed.
A total of 7,907 cases of infectious keratitis over three years were identified, for which cultures were performed in 6,001 (75.9%) and positive in 3,253 (41.1%). Of the positive culture cases, 2,163 (66.5%) and 1,027 (31.6%) were of fungal and bacterial etiology, respectively. The predominant fungal organisms were Fusarium (41.4%) and Aspergillus (16.6%) and the predominant bacterial organisms were Streptococcus pneumoniae (40.7%), Pseudomonas aeruginosa (27.1%), and Nocardia species (9.7%). Analyses revealed an uneven distribution of fungal keratitis throughout the year (p<0.001) with two peaks reproduced in all three years: a major peak centered in August and a smaller peak centered in January. An uneven distribution was observed for bacterial keratitis as well (p<0.001) but time patterns were less pronounced.
Fungal keratitis predominates in the tropical climate of South India, with a 2:1 ratio compared to bacterial keratitis. A higher incidence of fungal keratitis occurs during the humid Southwest monsoon season and the harvest season, the latter of which likely results from increased susceptibility to infection from vegetative corneal injury. More robust public health screening efforts during these periods may mitigate visually debilitating sequelae from infectious keratitis.
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