Characterization of a human isolate of Tritrichomonas foetus (cattle/swine genotype) infected by a zoonotic opportunistic infection.

Tritrichomonas species flagellates (IMC strain) were isolated from the biliary tract of an individual who had developed cholecystitis as a complication of acquired agammaglobulinemia. Sequence analysis of Tritrichomonas sp. (IMC clone 2 (cl2)) was performed for several genetic regions including the ITS1-5.8S rDNA-ITS2 region, the cysteine protease (CP)-1, CP-2 and CP-4 to CP-9 genes, and the cytosolic malate dehydrogenase 1 gene. In addition to comparison of the variable-length DNA repeats in the isolate clone with those in T. foetus (Inui cl2) and the T. mobilensis (U.S.A.: M776 cl2) reference strains, this analysis showed that the Tritrichomonas sp. (IMC cl2) was T. foetus (cattle/swine genotype). Injection of T. foetus (IMC cl2) directly into the livers of CBA mice resulted in liver abscess formation on Day 7. Moreover, inoculation via orogastric intubation caused infection in the cecum on Day 5 in CBA mice co-infected with Entamoeba histolytica (HM-1: IMSS cl6). T. foetus (IMC cl2) was able to grow in YI-S medium for over 20 days, even at 5°C. These results indicate that the T. foetus isolate is able to survive in the feces and edible organ meat of the definitive host for a prolonged period of time, and it is possible that the parasite could infect humans.