Comparison of Selected Pathogenic and Environmental Strains of Acanthamoeba

Signature Grand, Davie, Florida, USA

Objective. Because of a recent increase in the incidence of Acanthamoeba Keratitis, we studied the effect of temperature on the growth of 3 environmental strains (2 from tap water (TIV and MS26), one from a moist rock wall (BP)) along with 2 pathogenic corneal strains of Acanthamoeba (MW101 and MW102). Methods. Each molecularly typed strain was grown on amoeba saline (non-nutrient) agar plates with E. coli as prey. The plates were incubated at 20, 30, and 40oC, and the number of trophozoites was recorded daily. Results. The 2 corneal pathogens and one tap water strain (TIV) displayed significantly higher levels of growth (P<.001) within and between each of the tested temperatures when compared with the environmental strains BP and MS26. Actual growth was greatest for all strains at 30oC and slowest at 40oC. Differences in growth between the corneal isolates were not significantly different. Likewise growth between the two environmental strains BP and MS26 was not significantly different. Conclusion. It appears the pathogenic strains (both T-4) and the TIV tap water strain (T-5) were more aggressive in their growth characteristics than the environmental isolates BP (T-5) and MS26 (T-4). While molecular genotyping does not appear to indicate pathogenicity, higher growth levels may be an indication of pathogenicity due to adaptation to host temperatures. Grants. This study was funded by a NSU President’s Research & Development Award (SS & HL).