|CARLSON, STEVE - ISU
Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/2008
Publication Date: N/A
Technical Abstract: Salmonella is a foodborne pathogen that is persistently present in some cattle herds. Some animals are carriers while other animals appear resistant to colonization, despite their constant exposure to this pathogen. One explanation for this phenomenon may be that the microbiota of resistant animals effectively excludes Salmonella from the intestinal tract, a concept known as competitive exclusion. Competitive exclusion bacteria presumably prevent colonization of the gastrointestinal tract by pathogenic organisms through antibacterial agents, immune exclusion, or competitive adhesion. The objective of this work was to isolate an anti-Salmonella bacterium that may control pathogen load in persistently-infected cattle herds. To achieve this objective, we tested 19 fecal samples from Salmonella-positive (11 samples) and Salmonella-negative (8 samples) cattle for anti-Salmonella activity. An Escherchia coli designated as P8E5 was isolated from a Salmonella-negative fecal sample that possessed anti-Salmonella activity. The inhibitory affect of P8E5 was demonstrated by a 5 log reduction in viability of Salmonella enterica serovar Typhimurium (S. Typhimurium) that was co-incubated with P8E5 for 8 days. Similarly, quantitative PCR analysis of fecal samples collected over several days from neonatal Holstein calves that were co-administered S. Typhimurium and P8E5 showed a 3 to 4 log decrease in fecal shedding of S. Typhimurium. Furthermore, in vitro exposure of E. coli O157:H7 and Klebsiella pneumoniae to P8E5 also resulted in reduced viability of these two important human pathogens. In conclusion, E. coli P8E5 possesses a putative bacteriocin-like activity that effectively reduced both the in vitro and in vivo viability of Salmonella. This suggests that the presence of this E. coli, as a member of the native microbiota, dampens gastrointestinal colonization of Salmonella.