Microbiome Profiling of Enterotoxigenic Escherichia coli (ETEC) Carriers Highlights Signature Differences between Symptomatic and Asymptomatic Individuals

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea in children in low- and middle-income countries (LMICs). However, large-scale pathogen burden studies in children have identified ETEC in the guts of both symptomatic patients and controls. The factors that influence this balance are poorly understood, but it is postulated that the gut microbiome may play a role in either resistance or progression to disease. In this study, we profiled the microbiomes of children and adults from Bangladesh who were asymptomatically or symptomatically infected with ETEC. Symptomatic patients had significantly higher numbers of sequenced reads mapping to both E. coli and two ETEC toxins, suggesting higher bacterial burden. They were also significantly more likely to be coinfected with enteroaggregative E. coli (EAEC) and had higher proportions of other Gammaproteobacteria, including Klebsiella, Salmonella, and Haemophilus. Colonization with ETEC was also associated with increased prevalence of antimicrobial resistance (AMR) genes, most notably those of the b-lactamase class. Taxonomic profiles were distinctly different between all groups in both species richness and composition, although the direction of these changes was different in adults and children. As seen previously, children with high E. coli burdens also had higher proportions of Streptococcus spp., while healthy children were more heavily colonized by Bifidobacterium spp. Our study provides insight into the microbiome changes that occur upon infection with ETEC in an endemic setting and provides rationale for future studies investigating how the microbiome may protect or predispose individuals to symptomatic infections with gastrointestinal pathogens.