|MIR, RAIES - Orise Fellow|
|SCHAUT, ROBERT - Orise Fellow|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/22/2018
Publication Date: N/A
Technical Abstract: Cattle are primary reservoir of Shiga toxin-producing Escherichia coli (STEC). Field studies indicate STEC colonization influences gut microbiota composition in beef and dairy cattle. In this pilot study, we evaluated the bovine gut microbiota after STEC O157 (O157) challenge under experimental conditions. Four Jersey steers were orally challenged with10**10 CFU of a streptomycin-resistant O157 strain 86-24, and four were not challenged. To evaluate shedding, ten-fold serial dilutions of feces (collected by rectal palpation of cattle at 20 different time points) were plated on sorbitol-MacConkey agar containing streptomycin and potassium tellurite directly or after enrichment in trypticase soy-bile salts (0.1 percent) broth. To evaluate changes in intestinal microbiota total DNA was extracted from feces (n equals 160) using PowerSoil DNA extraction kit (Qiagen®) and the V4 region of microbial 16S rRNA gene sequenced on Miseq platform (Illumina®). Sequences were analyzed using the CLC microbial genomics module (Qiagen®). A total of 4.89 million reads generated by this analysis (average 30618 reads/sample) allowed prediction of 4931 Operational Taxonomic Units (OTU). Alpha diversity (combined over time) was not significantly different in the challenged versus non-challenged cattle. However, the alpha diversity (species richness and Shannon Entropy) was significantly different between sampling time points in the challenged cattle before and after challenge (P less than 0.05); but not in the non-challenged cattle (P greater than 0.3). The Firmicutes: Bacteroidetes ratio varied significantly between animals in both groups (ANOVA, P less than 0.05) but the time effect was significant only in the control group (P equals 0.001). The relative abundance of Proteobacteria increased over time among all animals independent of O157 challenge (P greater than 0.05). Differential abundance analysis (DAA) of the family-level OTUs indicated that Paenibacillaceae was higher in O157 shedding cattle and Planococcaceae was higher in non-shedding cattle. DAA also indicated higher abundance of Gardnerella in O157 shedding and Lysinibacillus in non-shedding cattle. Permanova analysis showed significant differences in microbial diversity (beta-diversity) between O157-shedding and non-shedding animals (P-value less than 0.001). We are presently analyzing genera that contribute to differences in microbial diversity in response to O157 colonization; analyzing such potential correlations could help develop strategies to reduce O157 colonization of the bovine gut in the future.