Exposure to Parasitic Protists and Helminths Changes the Intestinal Community Structure of Bacterial Communities in a Cohort of Mother-Child Binomials from a Semirural Setting in Mexico.

An estimated 3.5 billion people are colonized by intestinal parasites worldwide. Intestinal parasitic eukaryotes interact not only with the host but also with the intestinal microbiota. In this work, we studied the relationship between the presence of multiple enteric parasites and the community structures of gut bacteria and eukaryotes in an asymptomatic mother-child cohort from a semirural community in Mexico. Fecal samples were collected from 46 mothers and their respective children, with ages ranging from 2 to 20 months. Mothers and infants were found to be multiparasitized by Blastocystis hominis, Entamoeba dispar, Endolimax nana, Chilomastix mesnili, Iodamoeba butshlii, Entamoeba coli, Hymenolepis nana, and Ascaris lumbricoides. Sequencing of bacterial 16S rRNA and eukaryotic 18S rRNA genes showed a significant effect of parasite exposure on bacterial beta-diversity, which explained between 5.2% and 15.0% of the variation of the bacterial community structure in the cohort. Additionally, exposure to parasites was associated with significant changes in the relative abundances of multiple bacterial taxa, characterized by an increase in Clostridiales and decreases in Actinobacteria and Bacteroidales. Parasite exposure was not associated with changes in intestinal eukaryote relative abundances. However, we found several significant positive correlations between intestinal bacteria and eukaryotes, including Oscillospira with Entamoeba coli and Prevotella stercorea with Entamoeba hartmanni, as well as the co-occurrence of the fungus Candida with Bacteroides and Actinomyces, Bifidobacterium, and Prevotella copri and the fungus Pichia with Oscillospira. The parasitic exposure-associated changes in the bacterial community structure suggest effects on microbial metabolic routes, host nutrient uptake abilities, and intestinal immunity regulation in host-parasite interactions. IMPORTANCE The impact of intestinal eukaryotes on the prokaryotic microbiome composition of asymptomatic carriers has not been extensively explored, especially in infants and mothers with multiple parasitic infections. In this work, we studied the relationship between protist and helminth parasite colonization and the intestinal microbiota structure in an asymptomatic population of mother-child binomials from a semirural community in Mexico. We found that the presence of parasitic eukaryotes correlated with changes in the bacterial gut community structure in the intestinal microbiota in an age-dependent way. Parasitic infection was associated with an increase in the relative abundance of the class Clostridia and decreases of Actinobacteria and Bacteroidia. Parasitic infection was not associated with changes in the eukaryote community structure. However, we observed strong positive correlations between bacterial and other eukaryote taxa, identifying novel relationships between prokaryotes and fungi reflecting interkingdom interactions within the human intestine.

Prevalent HLA Class II Alleles in Mexico City Appear to Confer Resistance to the Development of Amebic Liver Abscess.

Amebiasis is an endemic disease and a public health problem throughout Mexico, although the incidence rates of amebic liver abscess (ALA) vary among the geographic regions of the country. Notably, incidence rates are high in the northwestern states (especially Sonora with a rate of 12.57/100,000 inhabitants) compared with the central region (Mexico City with a rate of 0.69/100,000 inhabitants). These data may be related to host genetic factors that are partially responsible for resistance or susceptibility. Therefore, we studied the association of the HLA-DRB1 and HLA-DQB1 alleles with resistance or susceptibility to ALA in two Mexican populations, one each from Mexico City and Sonora. Ninety ALA patients were clinically diagnosed by serology and sonography. Genomic DNA was extracted from peripheral blood mononuclear cells. To establish the genetic identity of both populations, 15 short tandem repeats (STRs) were analyzed with multiplexed PCR, and the allelic frequencies of HLA were studied by PCR-SSO using LUMINEX technology. The allele frequencies obtained were compared to an ethnically matched healthy control group (146 individuals). We observed that both affected populations differed genetically from the control group. We also found interesting trends in the population from Mexico City. HLA-DQB1*02 allele frequencies were higher in ALA patients compared to the control group (0.127 vs 0.047; p= 0.01; pc= NS; OR= 2.9, 95% CI= 1.09-8.3). The less frequent alleles in ALA patients were HLA-DRB1*08 (0.118 vs 0.238 in controls; p= 0.01; pc= NS; OR= 0.42, 95% CI= 0.19-0.87) and HLA-DQB1*04 (0.109 vs 0.214; p= 0.02; pc= NS; OR= 0.40, 95% CI= 0.20-0.94). The haplotype HLA-DRB1*08/-DQB1*04 also demonstrated a protective trend against the development of this disease (0.081 vs. 0.178; p=0.02; pc=NS; OR= 0.40, 95% CI= 0.16-0.93). These trends suggest that the prevalent alleles in the population of Mexico City may be associated with protection against the development of ALA.

Worldwide genealogy of Entamoeba histolytica: an overview to understand haplotype distribution and infection outcome.

Although Entamoeba histolytica is one of the most prevalent intestinal parasites, how the different strains of this species are distributed all over the world and how different genotypes are associated with the infection outcome are yet to be fully understood. Recently, the use of a number of molecular markers has made the characterization of several genotypes in those regions with high incidence of amoebiasis possible. This work proposes the first genealogy of E. histolytica, with an haplotype network based on two tRNA gene-linked array of Short Tandem Repeats (STRs) reported until today, and 47 sequences from 39 new isolates of Mexican Amoebic Liver Abscesses (ALA) samples. One hundred and three sequences were obtained from D-A locus, their information about the geographic region of isolation as well as clinical diagnosis were also collected. One hundred and five sequences from N-K2 locus were also obtained as well as the region of isolation, but the information about clinical diagnosis was not available in all cases. The most abundant and widely distributed haplotype in the world is the one of E. histolytica HM1:IMSS strain. This was found in Mexico, Bangladesh, Japan, China and USA and is associated to symptomatic patients as well as asymptomatic cyst passers. Many other haplotypes were found only in a single country. Both genealogies suggest that there are no lineages within the networks that may be related to a particular geographic region or infection outcome. A concatenated analysis of the two molecular markers revealed 12 different combinations, which suggests the possibility of genetic recombination events. The present study is the first to propose a global genealogy of this species and suggests that there are still many genotypes to be discovered. The genotyping of new isolates will help to understand the great diversity and genetic structure of this parasite.