Clinical Features and Gut Microbiome of Asymptomatic Entamoeba histolytica Infection

BACKGROUND: Entamoeba histolytica infection is a sexually transmitted disease in some developed countries. Asymptomatic infection often occurs and can be a source of transmission; however, limited data are available regarding the pathogenesis of E. histolytica. METHODS: This was a single-center, cross-sectional study. Specimens were prospectively collected from patients with clinically suspected cases. Entamoeba histolytica infection was defined as a case in which the identification of E. histolytica was confirmed by polymerase chain reaction (PCR) of a clinical specimen. Data from asymptomatic cases were compared with those from symptomatic invasive cases. RESULTS: Sixty-four E. histolytica–infected cases, including 13 asymptomatic cases, were identified during the study period. Microbiological diagnosis was made by endoscopic sampling in 26.6% of these cases (17/64). Endoscopy identified macroscopically visible lesions in all cases; however, the sensitivity of histopathology on biopsy samples was low (45.5%) compared with PCR (94.7%). In asymptomatic cases, infection sites were limited around the proximal colon; moreover, trophozoites were frequently identified at infection sites whereas cystic forms were commonly detected in stools. Gut microbiome analyses showed more uniform composition in asymptomatic cases than in symptomatic invasive cases, which were represented by a relatively high abundance of Ruminococcaceae, Coriobacteriaceae, and Clostridiaceae, and a low abundance of Streptococcaceae. CONCLUSIONS: These results indicate that the encystation and attenuation of E. histolytica are highly affected by the intestinal contents, including the gut microbiome.