Biological, Epidemiological and Clinical Studies on Amebic Infection among Institutionalized Populations

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Epidemiological and clinical studies were attempted for residents in institutions, who shoed high infection rates with Entamoeba histolytica. Biological analyses were also conducted on the ameba isolates from such individuals. The epidemiological analyses demonstrated as high as 30% positive rate by the specific antigen detection method and the conventional stool examination. However, most of the infected seemed to be due to the persistent asymptomatic infections with E.histolytica. Several strains of E.histolytica isolated from such individuals with the persistent infection showed genetic and antigenic properties consistent with those of E.histolytica ; however, they did show virtually no virulence against tissue-cultured cells as examined with a sensitive fluorescent method. Based on the base sequence polymorphism of 4 different genes like chitinase gene, identification of genetic types of subpopulations of E.histolytica was developed, and applied to the isolates from several institu … More tions. The analyses demonstrated that the isolates from a single institution showed entirely the same genetic type, suggesting that only single infected individual is responsible for expansion of the amebic infection.Further studies indicated that the gene type at a few institutions with rather high infection rates was exactly the same as that detected in the fist outbreak in Kanagawa Prefecture, and demonstrated that an infected individuals had moved from the institute in Kanagawa to these new institutions. This method was also applied to the ameba isolates from foreign countries lice Thailand. However, virtually no coincidence was detected between these foreign isolates and domestic strains. Trials of axenic cultivation of Entamoeba dispar, nonpathogenic ameba, was also actively conducted, which finally resulted in a newly designed YIGADHA-S medium, which allowed complete axenic cultivation of this ameba. Biological characterization of ameba isolates was also attempted by examining the process of excystation and sulfur containing amino acid metabolism, which resulted in discovery of several novel inhibitors. The possibility of these inhibitors as lead compounds for drug development will be investigated. The experimental model for abscess formation was produced by using a Syrian golden hamster cheek pouch. Less