Fates of Acid-Resistant and Non-Acid-Resistant Shiga Toxin-Producing Escherichia coli Strains in Ruminant Digestive Contents in the Absence and Presence of Probiotics

Abstract

Healthy ruminants are the main reservoir of Shiga toxin-producing Escherichia coli (STEC). During their transit through the ruminant gastrointestinal tract, STEC encounters a number of acidic environments. As all STEC strains are not equally resistant to acidic conditions, the purpose of this study was to investigate whether acid resistance confers an ecological advantage to STEC strains in ruminant digestive contents and whether acid resistance mechanisms are induced in the rumen compartment. We found that acid-resistant STEC survived at higher rates during prolonged incubation in rumen fluid than acidsensitive STEC and that they resisted the highly acidic conditions of the abomasum fluid, whereas acid-sensitive strains were killed. However, transit through the rumen contents allowed acid-sensitive strains to survive in the abomasum fluid at levels similar to those of acid-resistant STEC. The acid resistance status of the strains had little influence on STEC growth in jejunal and cecal contents. Supplementation with the probiotic Saccharomyces cerevisiae CNCM I-1077 or Lactobacillus acidophilus BT-1386 led to killing of all of the strains tested during prolonged incubation in the rumen contents, but it did not have any influence in the other digestive compartments. In addition, S. cerevisiae did not limit the induction of acid resistance in the rumen fluid. Our results indicate that the rumen compartment could be a relevant target for intervention strategies that could both limit STEC survival and eliminate induction of acid resistance mechanisms in order to decrease the number of viable STEC cells reaching the hindgut and thus STEC shedding and food contamination.

A study on gastrointestinal tract characteristics of ram lambs at the same weights from six Turkish sheep breeds

“…Therefore the feed efficiency of lambs from KY and MK breeds may be higher than those of the KV breed. On the other hand, volatile fatty acid concentrations are high in the rumen of grain-fed animals, and the pH may vary from 5.0 to 6.5, whereas in hay-fed animals, less fermentation occurs in the rumen, and the pH remains between 6.5 and 7 (Chaucheyras-Durand et al, 2010). Accordingly, less fermentation in the rumen of TM and AK ram lambs might have occurred than in the KY and MK lambs.…”

“…There has been insufficient information on some GIT characteristics such as absolute and relative (to body weight) weights of the whole GIT, reticulo-rumen and intestine, length of intestine and on the development of the GIT in these breeds when they were reared under the same feeding conditions (high-energy diet). The pH in the GIT content was 6.9, 7.3, 7.0 and 7.2 for the rumen, ileum, caecum and terminal colon, respectively, and the pH values of digesta from ruminants fed hay diets remained near neutrality in all segments of the GIT except the abomasum (Wheeler, 1980;Chaucheyras-Durand et al, 2010). However, a search of the literature indicated a lack of information on the pH of ingesta in the lower GIT of ram lambs fed high-energy diets.…”

Influence of rumen contents’ processing method on microbial populations in the fluid and subsequent in vitro fermentation of substrates of variable composition

“…F. succinogenes is a particularly important species for fiber digestion in the rumen, being metabolically active on less digestible fiber tissues (Koike and Kobayashi, 2009), and its greater abundance in STO inoculum could help to explain the observed increase in the DMD and TDMD of the substrates when they were incubated with STO inoculum. Among the major cellulolytic communities, ruminococci are major contributors to H 2 production (Chaucheyras-Durand et al, 2010), and the greater proportion of R. albus in STO inoculum agrees with the higher methane production after 8 and 24 h of incubation. The lack of significant differences between SQ and FL inoculum in any of the microbial populations analysed might indicate that those associated to the small feed particles added with SQ inoculum did not represent a significant contribution to total microbial populations.…”

An evaluation of the use of probiotics and manure composting as strategies to reduce levels of Shiga toxin-producing Escherichia coli in sheep

“…Importantly, STECs are zoonotic pathogens that can cause food-borne diseases in humans, ranging from diarrhea to hemorrhagic colitis (HC) and severe cases such as hemolytic uremic syndrome (HUS) (World Health Organization, 1998). Worldwide, sheep have been shown to be a major reservoir for STEC, including countries such as Norway (Urdahl et al, 2001), Russia (Kudva et al, 1998), Germany (Beutin et al, 2004), Spain (Rey et al, 2003) and Brazil (Vettorato et al, 2003) Probiotics may be used as an alternative for decreasing the number of pathogenic bacteria, thereby decreasing the spread of these strains on a farm (Lema et al, 2001;Chaucheyras-Durand et al, 2010). The mechanisms by which probiotics cause microbial interference in the gut include nutrient competition, generation of an unfavorable environment and competition for attachment or adhesion sites resulting in reduced colonization by pathogenic bacteria (Caplice and Fitzgerald, 1999).…”

“…The use of probiotic strains to supplement the ration of livestock (Lema et al, 2001;Chaucheyras-Durand et al, 2010) and the use of composting to decrease the population of pathogenic microbes (Pourcher et al, 2005;Murkherjee et al, 2006;Gonçalves and Marin, 2007) have both been reported as efficient alternatives to decrease the spread of pathogenic strains on a farm. However, these studies were done separately, and there is little information about the combined use of the two practices to decrease the STEC population present on a sheep farm.…”