Isolation and identification of Acanthamoeba species related to amoebic encephalitis and nonpathogenic free-living amoeba species from the rice field

Aims: Isolation and characterization of the clinically relevant amphizoic amoebas in vegetated farmlands, which may present a risk to farmers' health. Methods and Results: Acanthamoeba species was isolated and characterized via morphological and molecular means in the rice field where the patient was exposed to rice paddy water which most probably was the point of infection. An Acanthamoeba sp. abundant in the rice field was identified. Genotyping showed the strain to be genotype T4, which was identical to the amoebic parasite found in patient's cerebrospinal fluid. During the course of the study, three nonpathogenic free-living amoeba species were also isolated and characterized for the first time in Taiwan. Conclusions: This study successfully located a possible source of granulomatous amoebic encephalitis in a patient and provided the first evidence that Acanthamoeba genotype T4 may be a potential pathogen in Taiwan. Significance and Impact of the Study: The integration of field survey, clinical data and morphological and genetic examination represents a sound strategy for investigation of the possible role of free-living amoebae in causing human diseases. Future work should include investigating the potential contributory role of other nonpathogenic free-living protozoa in disease of livestock or even human.