Abstract
Purpose: :
To update and document recovery rates of Acanthamoeba and other free living amoeba from ocular and environmental sources during pre and post hurricane months in South Florida from December 1999– November 2005.
Methods: :
Laboratory records of all cultures submitted were evaluated to document culture positive rates, detection time, sources and mixed infections. Recovery rates were compared for three time periods, period 1 (three months prior to hurricane season –Mar–May) period 2 (6 months of hurricane season–June–November), and period 3 (3 months post hurricane–Dec–Feb). Environmental samples from eyewash stations, ice machines and seawater were collected and evaluated during the same period.
Results: :
Annual culture positive rate was 6% (52/865) and ranged from 4.5%–6.6%. Ninety–two percent (N=48) were identified as Acanthamoeba species, 4% as Vahlkampfia species and 4% other free–living amoeba species. 77% of positive cultures were detected within 72 hours on agar agar. 88% of isolates were from cornea scraping or biopsy. Bacteria coinfections (P. aeruginosa, S. marescens and P. acnes were document in 5.8% (3/52) of the cultures. Amoeba was isolated from contact lenses in 12% of cases. Recovery rates for the three time periods were 8.4% (pre hurricane), 5.2% (hurricane season) and 5.4% (post hurricane). Recovery rate for the months following the hurricane was 6.9% (28/407) vs. 5.2% (24/458) for months during the hurricane. Frequency of culture positive rates from environmental cultures were 14% (2/14) from seawater and <1% for eyewash stations (2/218).
Conclusions: :
Acanthamoeba and other free–living amoeba remain infrequent keratitis pathogens in South Florida. A higher, but not significant number of Acanthamoeba cases occurred in months following hurricane season. Laboratory confirmation remains an important adjunct in diagnosis amoebic keratitis.
Keywords: Acanthamoeba • clinical laboratory testing • keratitis