Biotic and Abiotic Factors Influencing In Vitro Growth of Escherichia coli O157:H7 in Ruminant Digestive Contents

Abstract

The gastrointestinal tract (GIT) of ruminants is the main reservoir of enterohemorrhagic Escherichia coli, which is responsible for food-borne infections in humans that can lead to severe kidney disease. Characterization of biotic and abiotic factors that influence the carriage of these pathogens by the ruminant would help in the development of ecological strategies to reduce their survival in the GIT and to decrease the risk of contamination of animal products. We found that growth of E. coli O157:H7 in rumen fluid was inhibited by the autochthonous microflora. Growth was also reduced when rumen fluid came from sheep fed a mixed diet composed of 50% wheat and 50% hay, as opposed to a 100% hay diet. In fecal suspensions, E. coli O157:H7 growth was not suppressed by the autochthonous flora. However, a probiotic strain of Lactobacillus acidophilus inhibited E. coli O157:H7 growth in fecal suspensions. The inhibitory effect was dose dependent. These lactic acid bacteria could be a relevant tool for controlling O157:H7 development in the terminal part of the ruminant GIT, which has been shown to be the main site of colonization by these pathogenic bacteria.Enterohemorrhagic Escherichia coli (EHEC) is a food-borne pathogen that causes human diseases ranging from uncomplicated diarrhea to hemorrhagic colitis and life-threatening complications, such as the hemolytic-uremic syndrome. Cattle and other ruminants appear to be the main reservoir of EHEC strains. Human contamination occurs mainly through consumption of undercooked ground beef, water, or dairy products contaminated by bovine feces (2). It is clear that on-farm strategies that decrease the carriage of EHEC strains by ruminants would help to reduce the risk of food-borne disease in humans (51).Experimental infections of ruminants have shown that the shedding of EHEC O157:H7 is a relatively transient event, with a mean duration of 14 days to 1 month (3,7,22,46). Dietary factors can influence the resistance of cattle to transient E. coli O157:H7 colonization. However, studies investigating the effect of diet on the fecal shedding of E. coli O157:H7 are in some conflict due to considerable individual variability (see reference 9 for a review). In some studies, it appeared that hay-fed sheep or cattle shed E. coli O157:H7 longer than grain-fed animals (25, 33, 54). However, high-fiber diets have been reported to clear E. coli O157:H7 completely from the gastrointestinal tract (GIT), in contrast to low-fiber diets (32). Studies that have investigated the digestive location of EHEC in ruminants are also controversial. However, most studies have identified the lower GIT as the site of E. coli O157:H7 persistence and proliferation (34, 54). In experimentally inoculated calves, as well as in naturally infected animals, recent reports describe E. coli O157:H7 colonization at the terminal rectum in an area rich in lymphoid follicles (37, 38).In vitro studies have shown that E. coli O157:H7 grows poorly in rumen fluid collected from recently fed cattle (within 4 h) and sup...

Effects of Dried Distillers’ Grain on Fecal Prevalence and Growth of Escherichia coli O157 in Batch Culture Fermentations from Cattle

“…In the intestine of ruminants, the microbial counts in the colon and rectum were higher than the counts at any other location (39). Fecal microbial suspensions used during in in vitro fermentation studies of sheep were shown to have microbial counts representative of the counts in the colon and rectum (7). In addition, the fermentation processes and microbial populations in the rumen differ from those in the hindgut (29), so fecal microbial fermentations may represent hindgut fermentation better than ruminal fermentations.…”

Effects of direct-fed microbial supplementation on digestibility and fermentation end-products in horses fed low- and high-starch concentrates1

“…al., 2002). It tolerates low pH and has antibiotic activity against E. coli O157:H7 (Ogawa et al, 2001;Chaucheyras-Durand et al, 2006).…”

“…Amylolytic bacteria are effective in inhibiting pathogens. Amylolytic LAB eliminated intestinal Escherichia coli 0157:H7 through competitive attachment of the intestinal epithelium (Jones and Rutter, 1972, Muralidhara et al, 1977, Zhao et al, 1998Ohya et al, 2000;Chaucheyras-Durand et al, 2006) and exhibited antibacterial activity against pathogens such as E. coli, Salmonella typhimurium, Staphylococcus aureus, and…”

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

“…During the HW diet feeding period, rumen samples were collected once a week from the midventral sac 3 h after the morning feeding. These samples were processed under strictly anaerobic conditions as previously described (13), with minor modifications. Briefly, rumen digesta were collected in O 2 -free N 2 -saturated sterile flasks.…”

“…These conditions (temperature, oxygenation, and duration) were chosen to reflect the in vivo conditions for each digestive compartment. For the rumen samples, ground feed (40% hay, 60% wheat) was added (25 mg of mixed ground feed for 5 ml of rumen contents) to mimic a fermentation cycle, as previously described (13). Because probiotics need to be administered daily, they were added to the incubation tubes containing the digestive fluids from animals fed probiotics as previously described (13) to obtain a final concentration close to 3 ϫ 10 5 cells ml Ϫ1 of digestive contents.…”