R.C. Anderson

Evaluation of bacterial diversity in the rumen and feces of cattle fed different levels of dried distillers grains plus solubles using bacterial tag-encoded FLX amplicon pyrosequencing.

Dietary components and changes cause shifts in the gastrointestinal microbial ecology that can play a role in animal health and productivity. However, most information about the microbial populations in the gut of livestock species has not been quantitative. In the present study, we utilized a new molecular method, bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP) that can perform diversity analyses of gastrointestinal bacterial populations. In the present study, cattle (n = 6) were fed a basal feedlot diet and were subsequently randomly assigned to 1 of 3 diets (n = 2 cows per diet). In each diet, 0, 25, or 50% of the concentrate portion of the ration was replaced with dried distillers grain (DDGS). Ruminal and fecal bacterial populations were different when animals were fed DDGS compared with controls; ruminal and fecal Firmicute:Bacteroidetes ratios were smaller (P = 0.07) in the 25 and 50% DDG diets compared with controls. Ruminal pH was decreased (P < 0.05) in ruminal fluid from cattle fed diets containing 50% compared with 0% DDGS. Using bTEFAP, the normal microbiota of cattle were examined using modern molecular methods to understand how diets affect gastrointestinal ecology and the gastrointestinal contribution of the microbiome to animal health and production.

Probiotics, prebiotics and competitive exclusion for prophylaxis against bacterial disease

Abstract The microbial population of the intestinal tract is a complex natural resource that can be utilized in an effort to reduce the impact of pathogenic bacteria that affect animal production and efficiency, as well as the safety of food products. Strategies have been devised to reduce the populations of food-borne pathogenic bacteria in animals at the on-farm stage. Many of these techniques rely on harnessing the natural competitive nature of bacteria to eliminate pathogens that negatively impact animal production or food safety. Thus feed products that are classified as probiotics, prebiotics and competitive exclusion cultures have been utilized as pathogen reduction strategies in food animals with varying degrees of success. The efficacy of these products is often due to specific microbial ecological factors that alter the competitive pressures experienced by the microbial population of the gut. A few products have been shown to be effective under field conditions and many have shown indications of effectiveness under experimental conditions and as a result probiotic products are widely used in all animal species and nearly all production systems. This review explores the ecology behind the efficacy of these products against pathogens found in food animals, including those that enter the food chain and impact human consumers.

Evaluation of the bacterial diversity in cecal contents of laying hens fed various molting diets by using bacterial tag-encoded FLX amplicon pyrosequencing

Laying hens are typically induced to molt to begin a new egg-laying cycle by withdrawing feed for up to 12 to 14 d. Fasted hens are more susceptible to colonization and tissue invasion by Salmonella enterica serovar Enteritidis. Much of this increased incidence in fasted hens is thought to be due to changes in the native intestinal microflora. An alternative to feed withdrawal involves feeding alfalfa meal crumble to hens, which is indigestible by poultry but provides fermentable substrate to the intestinal microbial population and reduces Salmonella colonization of hens compared with feed withdrawal. The present study was designed to quantify differences in the cecal microbial population of hens (n=12) fed a typical layer ration, undergoing feed withdrawal, or being fed alfalfa crumble by using a novel tag bacterial diversity amplification method. Bacteroides, Prevotella, and Clostridium were the most common genera isolated from all treatment groups. Only the ceca of hens undergoing feed withdrawal (n=4) contained Salmonella. The number of genera present was greatest in the alfalfa crumble-fed group and least in the feed withdrawal group (78 vs. 54 genera, respectively). Overall, the microbial diversity was least and Lactobacillius populations were not found in the hens undergoing feed withdrawal, which could explain much of these hens sensitivity to colonization by Salmonella.

Variation in the faecal shedding of Salmonella and E. coli O157:H7 in lactating dairy cattle and examination of Salmonella genotypes using pulsed‐field gel electrophoresis

Aims:u2002 To examine the variability in faecal shedding of Salmonella and Escherichia coli O157:H7 in healthy lactating dairy cattle and to evaluate the genetic relatedness of Salmonella isolates.

Antimicrobial susceptibility and factors affecting the shedding of E. coli O157:H7 and Salmonella in dairy cattle.

Aims: To examine factors affecting faecal shedding of the foodborne pathogens Escherichia coli O157:H7 and Salmonella in dairy cattle and evaluate antimicrobial susceptibility of these isolates.

Effect of oral sodium chlorate administration on Escherichia coli O157:H7 in the gut of experimentally infected pigs

Strategies are sought to reduce pathogenic Escherichia coli concentrations in food animals. Because E. coli possess respiratory nitrate reductase activity, which also reduces chlorate to cytotoxic chlorite, we tested and found that oral sodium chlorate administration reduced gut concentrations of E. coli O157:H7 in experimentally infected pigs and wildtype E. coli concentrations in nonchallenged pigs. Mean +/- S.E. concentrations (log10 CFU/g) of E. coli O157:H7 in ileal, cecal, colonic and rectal contents from placebo-treated pigs were 4.03 +/- 0.66, 3.82 +/- 0.24, 4.42 +/- 0.25 and 4.03 +/- 0.16, respectively. In contrast, E. coli O157:H7 concentrations were reduced (P < 0.05) in ileal (1.56 +/- 0.22) cecal (2.65 +/- 0.38), colonic (3.05 +/- 0.38) and rectal (3.00 +/- 0.29) contents from pigs orally administered three successive (8 h apart) 10-ml doses of 100 mM chlorate. Wildtype E. coli concentrations in gut contents of non-E. coli O157:H7-challenged pigs likewise treated with chlorate were reduced by 1.1 to 4.5 log10 units compared to concentrations in placebo-treated pigs, which exceeded 6.0 log10 CFU/g. As before, the reductions were greater in anterior regions of the gut than regions more caudal. Similar treatment of E. coli O157:H7-challenged pigs with 200 mM chlorate caused reductions in gut concentrations of E. coli O157:H7; however, the reductions were not necessarily greater than those achieved with the 100 mM chlorate treatment.

Recent pre-harvest supplementation strategies to reduce carriage and shedding of zoonotic enteric bacterial pathogens in food animals

Abstract Food-borne bacterial illnesses strike more than 76 million North Americans each year. Many of these illnesses are caused by animal-derived foodstuffs. Slaughter and processing plants do an outstanding job in reducing bacterial contamination after slaughter and during further processing, yet food-borne illnesses still occur at an unacceptable frequency. Thus, it is imperative to widen the window of action against pathogenic bacteria. Attacking pathogens on the farm or in the feedlot will improve food safety all the way to the consumer’s fork. Because of the potential improvement in overall food safety that pre-harvest intervention strategies can provide, a broad range of preslaughter intervention strategies are currently under investigation. Potential interventions include direct anti-pathogen strategies, competitive enhancement strategies and animal management strategies. Included in these strategies are competitive exclusion, probiotics, prebiotics, antibiotics, antibacterial proteins, vaccination, bacteriophage, diet, and water trough interventions. The parallel and simultaneous application of one or more preslaughter strategies has the potential to synergistically reduce the incidence of human food-borne illnesses by erecting multiple hurdles, thus preventing entry of pathogens into the food chain. This review emphasizes work with Escherichia coli O157:H7 to illustrate the various strategies.

Reduction of E. coli O157:H7 populations in sheep by supplementation of an experimental sodium chlorate product

Ruminant animals are naturally infected with the pathogen Escherichia coli O157:H7, annually responsible for numerous meat recalls, foodborne illnesses and deaths. E. coli are equipped with the enzyme nitrate reductase, which not only enables this bacteria to respire anaerobically, but also converts chlorate to the toxic metabolite chlorite. This enzyme system is particular to only a few intestinal bacteria, therefore the vast majority are not affected by chlorate. Sodium chlorate has been shown to effectively decrease foodborne pathogens in several livestock species, including ruminants. However, because infection and proliferation of E. coli occurs primarily in the lower intestine, there is interest in “by-passing” the rumen, thereby, delivering chlorate directly to the largest population of pathogens. The objective of the current study was to evaluate the ability of an experimental sodium chlorate product (ECP II), designed to by-pass the rumen, in reducing fecal shedding and gut concentrations of E. coli O157:H7. Twenty crossbred mature ewes were adapted to a high grain ration and experimentally inoculated with E. coli O157:H7. Thirty-six hours following inoculation, sheep received in their feed one of the following ECP treatments: (1) control (CON), no chlorate; (2) 1X (LOW); (3) 2X (MED); and (4) 4X (HIGH) where X=1.1 g chlorate ion equivalents/kg BW (five sheep per treatment). Fecal samples were collected every 12 h following inoculation and 24 h following the feeding of chlorate, all animals were euthanized and tissue samples and their respective contents collected from the rumen, cecum and rectum. The MED and HIGH chlorate treatments significantly reduced fecal shedding of E. coli O157:H7 compared to the CON treatment [1.53, 1.11, and 3.89 CFU/g feces (log10), respectively]. Ruminal contents were similar among treatments, while chlorate tended to decrease (P=0.08) and reduced (P<0.05) E. coli O157:H7 populations in the cecum and rectum, respectively. Populations of generic E. coli in the cecal contents were numerically lower (P=0.11) in the LOW treatment and tended to decrease (P=0.06) in the MED and HIGH chlorate treatments, respectively. Fermentation profiles through the gastrointestinal tract were unaffected as indicated by slight, but not significant, changes in volatile fatty acids (VFA) profiles in sheep fed chlorate. Results from this study indicate that this experimental chlorate product, administered in the feed, was effective in reducing E. coli O157:H7 from the lower gut of sheep as evidenced by the lower cecal and rectal but not ruminal concentrations. Feeding chlorate may be an effective method to decrease E. coli O157:H7 populations in ruminant animals prior to slaughter.

Citrus Products Decrease Growth of E. coli O157:H7 and Salmonella Typhimurium in Pure Culture and in Fermentation with Mixed Ruminal Microorganisms In Vitro

Orange peel and orange pulp are by-products that are included in feedlot and dairy cattle diets because of their low cost and high nutritional quality. The antimicrobial activity of citrus oils has been reported previously. The present study was carried out to determine whether these citrus by-products exert antimicrobial effects on Escherichia coli O157:H7 and Salmonella Typhimurium populations that are found in cattle gastrointestinal tracts. The growth of pure cultures (n = 3) of E. coli O157:H7 and Salmonella Typhimurium were reduced (p < 0.05) by addition of 2% (w/v) orange pulp and orange peel. Ruminal fluid was collected from cattle (n = 2) and E. coli O157:H7 or Salmonella Typhimurium were added. The addition of orange pulp and peel to in vitro mixed ruminal microorganism fermentations (n = 3) demonstrated that both orange pulp and peel reduced E. coli O157:H7 and Salmonella Typhimurium populations at least 2 log(10) in mixed ruminal fluid fermentations. Addition of orange pulp reduced (p < 0.05) E. coli O157:H7 populations from 10(5) to 10(2) colony-forming units (CFU)/mL and Salmonella Typhimurium populations (p < 0.05) from 10(4) to 10(2) CFU/mL. These results indicate that orange pulp and/or peel included in ruminant diets could decrease ruminal populations of foodborne pathogenic bacteria. Further research is needed to determine whether the antimicrobial activity of orange products against E. coli O157:H7 or Salmonella Typhimurium is expressed in the lower gastrointestinal tract.

Investigation into the seasonal salmonellosis in lactating dairy cattle

Sporadic salmonellosis has been reported in mature lactating dairy cattle in the southwestern United States and is an intriguing problem in that Salmonella can be cultured from faecal samples of these cattle throughout the year. However, it is pathogenic only during late summer/early autumn and in certain years. We sampled apparently healthy (n=10) and diarrhoeic (n=10) cattle during an outbreak on a 2000 head dairy in 2003. The following year, monthly faecal (from the same 30 head), total mixed ration, water, and pen soil samples were collected for Salmonella culture. No serogroup, serotype, genetic, or antimicrobial susceptibility differences were observed in comparison of isolates from healthy and sick cattle. During year 2 of the study, Salmonella was routinely cultured (although highly variable from month to month) from the cattle and the environment, although no outbreak of salmonellosis was observed.