Short-Chain Fatty Acids in diarrhea caused by Diarrheagenic Escherichia coli in Children infections.

Diarrheagenic Escherichia coli (DEC) are a main cause of diarrhea in children under 5 years old. DEC virulence is strongly regulated by environmental signals conditioned by gut microbiota and its produced metabolites. Short-chain fatty acids (SCFAs) are the main metabolic products of anaerobic fermentation in the gut. There is growing evidence of the role that SCFAs might have on the regulation of the virulence of enteric pathogens, however their role on DEC diarrhea has not yet been established. In this work, we sought to determine the levels of acetate, propionate, and butyrate in stool samples from children with diarrhea caused by DEC and to identify the bacteria from gut microbiota associated with the production of SCFA. 40 stool samples obtained from children under 5 years of age with diarrhea and 43 from healthy children attending a daycare center were analyzed. Microbiota was determined using 16S rRNA gene sequences and levels of acetate, propionate and butyrate were determined using HPLC on 83 stool samples. Additionally, shotgun metagenomics was used in a subgroup of samples to evaluate the presence of genes associated with the production of acetate, propionate, and butyrate. Results showed significantly higher levels of all the SCFA tested in diarrheal samples compared to healthy controls. Abundance of Streptococcus sp, Limosilactobacillus, Blautia, Escherichia, Bacteroides, Megamonas, and Roseburia increased in the DEC group compared to healthy individuals. Functional analysis of bacteria and detected SCFA, showed associations of SCFA with specific species in the DEC group. In conclusion, our results highlight the role of SCFA in the crosstalk between the microbiota and DEC pathogens in the gut