|Mir, Raies - Orise Fellow|
|Schaut, Robert - Orise Fellow|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2018
Publication Date: N/A
Technical Abstract: Introduction: Cattle are the asymptomatic reservoirs of Escherichia coli O157:H7 (O157) that tend to preferentially colonize the bovine recto-anal junction (RAJ). Therefore, understanding the taxonomic profile, microbial diversity, and microbiota-O157 interactions at the RAJ could give insights into O157 colonization in cattle and their persistence at this site. Purpose: In this pilot study, we sought to determine if O157 colonization was associated with microbiota changes at the RAJ of cattle experimentally challenged with O157 in comparison to non-challenged cattle. Methods: Four Jersey steers were orally challenged with 10 to the power of 10 CFU of a streptomycin-resistant O157 strain 86-24, and four steers were mock-challenged. RAJ mucosal swab (RAMS) samples were collected from all steers at 20 different time points and plated on sorbitol-MacConkey agar containing streptomycin and potassium tellurite, directly or after enrichment, to detect O157 colonization. DNA was also extracted from RAMS (n equals 160) and used for sequencing the V4 region of microbial 16S rRNA gene on Miseq platform (Illumina®) to determine taxonomic profiles and assess microbial diversity using the CLC microbial genomics module (Qiagen®). Results: The Chao1 species richness (but not the Shannon Index) increased in samples collected after O157 challenge. The Firmicutes to Bacteroidetes (F: B) ratio and relative abundance of Proteobacteria were not associated with O157 colonization. Analysis of taxonomic assignments indicated significantly higher representation of the families Fusobacteriaceae and Paenibacillaceae in O157 shedding cattle. We also observed increased representation of Solibacillus and Eubacterium genera in non-shedding cattle. There was no difference in the beta-diversity between control and test samples before O157 challenge but the microbial diversity was significantly different between the two groups after O157 challenge. Significance: This study explores changes in microbiota composition at the bovine RAJ after O157 colonization, and understanding these changes may help develop strategies to reduce O157 colonization in cattle.