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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #412063

Research Project: Intestinal Microbial Ecology and Non-Antibiotic Strategies to Limit Shiga Toxin-Producing Escherichia coli (STEC) and Antimicrobial Resistance Transmission in Food Animals

Location: Food Safety and Enteric Pathogens Research

Title: The starvation-inducible sipoprotein (Slp) plays a role in Escherichia coli O157:H7 adherence to the bovine rectoanal junction

item BIERNBAUM, ERIKA - Oak Ridge Institute For Science And Education (ORISE)
item Cassmann, Eric
item Palmer, Mitchell
item EDISON, LEKSHMI - University Of Florida
item KARIYAWASAM, SUBHASHINIE - University Of Florida
item Kudva, Indira

Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Shiga toxin-producing Escherichia coli O157:H7 (O157) is a foodborne human pathogen. Cattle are asymptomatic O157 reservoirs; O157 persists at the rectoanal junction (RAJ) of the bovine intestinal tract. Identifying mechanisms used by O157 for initial adherence before persistence at the RAJ could help develop more effective O157 control modalities. We recently established the role of carbon starvation-inducible lipoprotein (Slp) in initial adherence of O157 to Caco-2 cells, with the human polymeric immunoglulin receptor (pIgR) protein as the Slp-receptor. Here we evaluated the role of Slp in O157 adherence to the bovine RAJ using in vitro assays with either the RAJ squamous epithelial (RSE) cells alone or including the columnar epithelial cells, namely the (i) RSE and (ii) RAJ-In vitro Organ Culture (IVOC) adherence assays. The wild-type O157 strain EDL932 (EDL932-WT), it’s isogenic Slp mutant (EDL932 'slp) and the mutant with Slp complementation (EDL932 'slp-p:slp), were tested; E. coli strain K12 and no bacteria controls were included. Adherence was evaluated by (i) non-enrichment and selective-enrichment culture and/or (ii) immunofluorescent (IF) staining of frozen tissue sections or RSE cells for O157. Tissue integrity was evaluated using the nucleus staining RedDot2 dye assay and histopathological examination of hematoxylin and eosin-stained tissue sections. A PCR-based DNA fingerprinting method was used for isolate verification during assays. All test strains adhered in a diffuse-moderate pattern on RSE cells. However, differential adherence was observed on the RAJ-IVOC, especially at the 107 cfu/ml inoculum concentration, with the strains preferentially adhering the columnar cells. Additionally, EDL932-WT and EDL932 'slp-p:slp strains adhered in slightly greater numbers than the mutant EDL932 'slp strain to the RAJ-IVOC. This distinction was better observed by IF microscopy. The RAJ-IVOC tissue integrity was maintained through out the assays with strain related disruption predominantly in the columnar/glandular region of the RAJ-IVOC; additional histological evaluations are ongoing. Interestingly, pIGR was detected by IF microscopy close to the mucosal surface of the columnar region of the RAJ-IVOC tissue where the test strains adhered. Further investigations into this observation are being planned. In conclusion, the RAJ-IVOC adherence assay results support the role for O157 Slp in initial adherence to the columnar cells at the bovine RAJ, unlike the squamous cells where the loss of Slp did not alter O157 adherence.