Role of the gut microbiota of children in diarrhea due to the protozoan parasite Entamoeba histolytica

Children in developing countries are continually exposed to enteric pathogens [1–4]. This results in high rates of morbidity and mortality, especially in infants [5]. The outcome of an Entamoeba histolytica exposure can be diarrhea, dysentery, or amebic liver abscess, with the latter occurring mainly in men [6]. Disease, however, occurs in a minority of E. histolytica infections (approximately 20%) [6]. While both host and parasite factors contribute to outcome, they do not entirely explain susceptibility [7–9]. A prospective longitudinal study of enteric pathogens in a slum community in Dhaka, Bangladesh, has provided a rich data set to identify parameters important for protection and disease. It has been previously shown that children in this study cohort who are malnourished at birth are more susceptible to amebiasis and in general experience more-severe diarrhea [2]. There is evidence in support of both passive and active acquired immunity. Infants with mothers with high levels of breast milk anti-galactose/N-acetylgalactosamine (Gal/GalNAc) lectin immunoglobulin A (IgA) had fewer E. histolytica infections, and children with fecal IgA anti-Gal/GalNAc lectin IgA also had a lower incidence of new infection [10, 11]. Weaning and the introduction of supplementary food into the diet is known to trigger changes in the bacterial composition of the microbiome that include increases in Prevotellaceae and Bacteroides species [12, 13]. The first 2 years of life in general is a period of rapid immune and microbiome maturation, which, in this population, may be disrupted by malnutrition and environmental insult [13–15]. Here we describe the natural history of amebiasis in the first 2 years of life in infants from an urban slum in Dhaka. The cumulative incidence of amebic infection and diarrhea, the association of protection with anti-Gal/GalNAc lectin IgA, the impact of parasite burden on symptoms, and potential role of Prevotella copri in E. histolytica diarrhea are described.