Comparative Effect of Direct-Fed Microbials on Fecal Shedding of Escherichia coli O157:H7 and Salmonella in Naturally Infected Feedlot Cattle

Abstract

The effect of direct-fed microbials (DFM) on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle was evaluated in a clinical trial involving 138 feedlot steers. Following standard laboratory methods, fecal samples collected from steers were evaluated for change in the detectable levels of E. coli O157:H7 and Salmonella shed in feces after DFM treatment. Sampling of steers was carried out every 3 weeks for 84 days. A significant reduction (32%) in fecal shedding of E. coli O157:H7 (P < 0.001), but not Salmonella (P = 0.24), was observed among the treatment steers compared with the control group during finishing. The probability of recovery of E. coli O157:H7 from the feces of treated and control steers was 34.0 and 66.0%, respectively. Steers placed on DFM supplement were almost three times less likely to shed E. coli O157:H7 (odds ratio, 0.36; 95% confidence interval, 0.25 to 0.53; P < 0.001) in their feces as opposed to their control counterparts. The probability of recovery of Salmonella from the feces of the control (14.0%) and the treated (11.3%) steers was similar. However, the DFM significantly reduced probability of new infections with Salmonella among DFM-treated cattle compared with controls (nontreated ones). It appears that DFM as applied in our study are capable of significantly reducing fecal shedding of E. coli O157:H7 in naturally infected cattle but not Salmonella. The factors responsible for the observed difference in the effects of DFM on E. coli O157:H7 and Salmonella warrants further investigation.

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

“…S. cerevisiae I-1077 has also been shown to affect the growth and activities of rumen microbial communities (14), so STEC inhibition could also be associated with a modified balance of the resident microbiota. L. acidophilus BT-1386 has been reported to limit the prevalence of O157:H7 in naturally infected feedlot cattle (40), and it inhibits the in vitro growth of E. coli O157:H7 in fecal suspensions (13). In this study, we found high concentrations of lactate in the rumen contents incubated with L. acidophilus, which presumably led to the observed decrease in pH.…”

“…Several studies have demonstrated the capacity of certain lactic acid bacteria or yeast to reduce E. coli O157:H7 counts in vitro (1,34) or in vivo (5,40). The mechanisms of action of probiotics are not well characterized but could involve competition for nutrients and adhesion sites in the GIT, an increase in the VFA concentration and a decrease in the pH, production of antimicrobial molecules, or interference with quorum-sensing signaling (27)(28)(29).…”

Survival of Escherichia coli in the environment: fundamental and public health aspects

“…Some organisms could be direct competitors by occupying the same niche, whereas others might have antagonistic or predatory activities. Isolation and identification of microorganisms that promote the decline of the invader may pinpoint inhibitory species, which might be applied as probiotics to reduce the survivability of pathogenic E. coli (Tabe et al, 2008). Conversely, the presence of cellulose-and lignindegrading organisms might provide E. coli with easily available carbon sources.…”

In vitro evaluation of celluloytic Bacillus amyloliquefaciens AMS1 isolated from traditional fermented soybean (Churpi) as an animal probiotic

“…Probiotics exert beneficial effects on the host by providing nutrients and enzymatic contribution to digestion, improving water quality, enhancing growth, inhibiting pathogenic microorganisms and enhancing immune responses (Balcazar et al, 2006;Verschuere et al, 2000). The supplementation of Lactic Acid Bacteria (LAB) as probiotics in ruminants has been extensively studied as compared with Bacillus probiotics (Brashears et al, 2003;Maragkoudakis et al, 2010;Peterson et al, 2007;Tabe et al, 2008;Younts-Dahl et al, 2004). However there are very few reports on cellulolytic activities of LAB.…”