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

Super Shedding in Enteric Pathogens: A Review

Super shedding occurs when a small number of individuals from a given host population shed high levels of a pathogen. Beyond this general definition, various interpretations of the shedding patterns have been proposed to identify super shedders, leading to the description of the super shedding phenomenon in a wide range of pathogens, in particular enteric pathogens, which are of considerable interest. Several underlying mechanisms may explain this observation, including factors related to the environment, the gut microbiota, the pathogen itself (i.e., genetic polymorphism), and the host (including immune factors). Moreover, data suggest that the interplay of these parameters, in particular at the host-pathogen-gut microbiota interface, is of crucial importance for the determination of the super shedding phenotype in enteric pathogens. As a phenomenon playing an important role in the epidemics of enteric diseases, the evidence of super shedding has highlighted the need to develop various control strategies.

Influence of sodium chlorate, ferulic acid, and essential oils on Escherichia coli and porcine fecal microbiota

The influence of sodium chlorate (SC), ferulic acid (FA), and essential oils (EO) was examined on the survivability of two porcine diarrhetic enterotoxigenic Escherichia coli (ETEC) strains (F18 and K88) and populations of porcine fecal bacteria. Fecal bacterial populations were examined by denaturing gradient gel electrophoresis (DGGE) and identification by 16S gene sequencing. The treatments were control (no additives), 10 mM SC, 2.5 mg FA /mL, a 1.5% vol/vol solution of an EO mixture as well as mixtures of EO + SC, EO + FA, and FA + SC at each of the aforementioned concentrations. EO were a commercial blend of oregano oil and cinnamon oil with water and citric acid. Freshly collected porcine feces in half-strength Mueller Hinton broth was inoculated with E. coli F18 (Trial 1) or E. coli K88 (Trial 2). The fecal-E. coli suspensions were transferred to crimp top tubes preloaded with the treatment compounds. Quantitative enumeration was at 0, 6, and 24 h. All treatments reduced (P < 0.05) the counts of E. coli F18 at 6 and 24 h. With the exception of similarity coefficient (%SC), all the other treatments reduced (P < 0.05) the K88 counts at 24 h. The most effective treatments to reduce the F18 and K88 CFU numbers were those containing EO. Results of DGGE revealed that Dice percentage similarity coefficients (%SC) of bacterial profiles among treatment groups varied from 81.3% to 100%SC. The results of gene sequencing showed that, except for SC at 24 h, all the other treatments reduced the counts of the family Enterobacteriaceae, while Lactobacillaceae and Ruminococcaceae increased and Clostridiaceae decreased in all treatments. In conclusion, all treatments were effective in reducing the ETEC, but EO mixture was the most effective. The porcine microbial communities may be influenced by the studied treatments.

Preharvest Food Safety Challenges in Beef and Dairy Production

Foods of animal origin, including beef and dairy products, are nutritious and important to global food security. However, there are important risks to human health from hazards that are introduced to beef and dairy products on the farm. Food safety hazards may be chemical, biological, or physical in nature. Considerations about protecting the safety of beef and dairy products must begin prior to harvest because some potential food safety hazards introduced at the farm (e.g., chemical residues) cannot be mitigated by subsequent postharvest food processing steps. Also, some people have preferences for consuming food that has not been through postharvest processing even though those foods may be unsafe because of microbiological hazards originating from the farm. Because of human fallibility and complex microbial ecologies, many of the preharvest hazards associated with beef and dairy products cannot entirely be eliminated, but the risk for most can be reduced through systematic interventions taken on the farm. Beef and dairy farms differ widely in production practices because of differences in natural, human, and capital resources. Therefore, the actions necessary to minimize on-farm food safety hazards must be farm-specific and they must address scientific, political, economic, and practical aspects. Notable successes in controlling and preventing on-farm hazards to food safety have occurred through a combination of voluntary and regulatory efforts.

Safety of using Escherichia coli bacteriophages as a sanitizing agent based on inflammatory responses in rats

Use of bacteriophages as sanitizing agents has received much attention. However, safety in humans is debatable. To determine inflammatory immune responses against bacteriophages, rats were treated with a 8 log plaque-forming cocktail of 5 bacteriophages for pathogenic Escherichia coli per day for 4 weeks. Food consumption, feeding efficiency, and body weight of rats treated with the cocktail were not different from controls. Phages were not detected in the sera of phage-fed rats with no changes in organ weights. Notable changes were not observed upon histopathological examination of the liver, kidney, and spleen. Pro-inflammatory cytokine mRNA expression, except COX-2 (2.4x increase), remained unaffected after treatment with the phage cocktail. No remarkable changes were observed for levels of 12 pro-inflammatory cytokines in sera. Inflammatory responses in rats orally treated with a phage cocktail were not observed. Bacteriophages for E. coli are indicated as immunologically safe in rats.

Continuous, low-dose oral exposure to sodium chlorate reduces fecal generic Escherichia coli in sheep feces without inducing clinical chlorate toxicosis

Our objectives were to determine an effective, yet safe, daily dose of sodium chlorate for reducing fecal shedding of generic Escherichia coli in mature ewes. In a completely randomized experimental design, 25 Targhee ewes (age ∼ 18 mo; BW = 62.5 ± 7.3 kg, mean ± SD) were assigned randomly to 1 of 5 sodium chlorate treatments, which were administered in the drinking water for 5 consecutive days. Treatments were control group (no sodium chlorate) and 4 targeted levels of daily sodium chlorate intake: 30, 60, 90, and 120 mg · kg(-1) BW · d(-1) for 5 d. Individual ewe ad libitum intake of water (with treatments) was measured daily, and BW was measured at the beginning of and 15 and 51 d after the 5-d treatment period. Serum chlorate, whole blood methemoglobin and packed-cell volume (PCV), and fecal generic E. coli and general Enterobacteriaceae coliforms were measured from corresponding samples collected at the end of the 5-d treatment period. Average daily intakes of sodium chlorate from drinking water treatments were 95%, 91%, 90%, and 83% of the target treatment intakes of 30, 60, 90, and 120 mg · kg(-1) BW · d(-1), respectively. Daily sodium chlorate intake remained constant for all treatment groups except for ewes offered 120 mg NaClO3 · kg(-1) BW · d(-1), which decreased (quadratic; P = 0.04) over the course of the 5-d treatment period. This decrease in sodium chlorate intake indicated that the 120-mg NaClO3 level may have induced either toxicity and/or an aversion to the drinking water treatment. Serum chlorate concentrations increased (quadratic; P < 0.001) with increasing sodium chlorate intake. At the end of the 5-d treatment period, mean (least squares ± SEM) serum chlorate concentrations for ewes offered 30, 60, 90, and 120 mg NaClO3 · kg(-1) BW · d(-1) were 15.6 ± 14.1, 32.8 ± 15.8, 52.9 ± 14.1, and 90.3 ± 14.1 μg/mL, respectively. Whole blood methemoglobin and PCV were similar (P = 0.31 to 0.81) among the control group and ewes offered sodium chlorate. Likewise, BW was not affected by sodium chlorate (P > 0.27). Ewes consuming approximately 55 mg NaClO3 · kg(-1) BW · d(-1) or more (i.e., ewes offered 60, 90, and 120 mg) had a >1.4 log unit reduction in fecal E. coli and Enterobacteriaceae coliforms compared with control ewes. We suggest that for a short-term, 5-d dosing strategy, 55 to 81 mg NaClO3 · kg(-1) BW · d(-1) is an effective, yet safe, daily oral dose range for mature ewes to achieve a 97% to 99% reduction in fecal shedding of generic E. coli.

Effect of repeated suboptimal chlorate treatment on ruminal and fecal bacterial diversity

The minimal effective dose of sodium chlorate as an intervention to reduce the carriage of pathogenic bacteria in food-producing animals has not been clearly established. The effect of low-level oral chlorate administration to ewes was assessed by comparing the diversity of prominent bacterial populations in their gastrointestinal tract. Twelve lactating crossed Pelibuey and Blackbelly-Dorper ewes (average body weight, 65 kg) were randomly assigned (four per treatment) to receive a control treatment (TC; consisting of 3 g of NaCl per animal per day) or one of two chlorate treatments (T3 or T9; consisting of 1.8 or 5.4 g of NaClO3 per animal per day, respectively). Treatments were administered twice daily via oral gavage for 5 days. Ruminal and fecal samples were collected daily, starting 3 days before and ending 6 days after treatment, and were subjected to denaturing gradient gel electrophoresis of the 16S rRNA gene sequence amplified from total population DNA. For ruminal microbes, percent similarity coefficients (SCs) between groups varied from 23.0 to 67.5% and from 39.4 to 43.3% during pretreatment and treatment periods, respectively. During the treatment period, SCs within groups ranged from 39.4 to 90.3%, 43.3 to 86.7%, and 67.5 to 92.4% for TC, T3, and T9, respectively. For fecal microbes, SCs between groups varied from 38.0 to 85.2% and 38.0 to 94.2% during pretreatment and treatment periods, respectively. SCs for fecal populations during treatment were most varied for TC (38.0 to 67.9%), intermediate for T9 (75.6 to 92.0%), and least varied for T3 (80.6 to 90.6%). Heterogeneity within and between groups provided no evidence of an effect of chlorate treatment on ruminal or fecal microbial populations.

Cattle Production Systems: Ecology of Existing and Emerging Escherichia coli Types Related to Foodborne Illness

Shiga toxin–producing Escherichia coli (STEC), particularly STEC O157, cause rare but potentially serious human infections. Infection with STEC occurs by fecal-oral transmission, most commonly through food. Cattle are the most important reservoir for human STEC exposure, and efforts to control the flow of STEC through beef processing have reduced rates of human illness. However, further reduction in human incidence of STEC may require control of the pathogen in cattle populations. The ecology of STEC in cattle production systems is complex and explained by factors that favor (a) colonization in the gut, (b) survival in the environment, and (c) ingestion by another cattle host. Although nature creates seasonal environmental conditions that do not favor STEC transmission in cattle, human efforts to control STEC by environmental manipulation have not succeeded. Vaccines and direct-fed microbial products have reduced the carriage of STEC by cattle, and other interventions are under investigation.

Effects of repeated-low level sodium chlorate administration on ruminal and fecal coliforms in sheep

Abstract The objective of this study was to evaluate the efficacy of oral sodium chlorate administration on reducing total coliform populations in ewes. A 30% sodium chlorate product or a sodium chloride placebo was administered to twelve lactating Dorper X Blackbelly or Pelibuey crossbred ewes averaging 65 kg body weight. The ewes were adapted to diet and management. Ewes were randomly assigned (4/treatment) to one of three treatments which were administered twice daily by oral gavage for five consecutive days: a control (TC) consisting of 3 g sodium chloride/animal/d, a T3 treatment consisting of 1.8 g of sodium chlorate/animal/d, and a T9 treatment consisting of 5.4 g sodium chlorate/animal/d; the latter was intended to approximate a lowest known effective dose. Ruminal samples collected by stomach tube and freshly voided fecal samples were collected daily beginning 3 days before treatment initiation and for 6 days thereafter. Contents were cultured quantitatively to enumerate total coliforms. There were no significant differences in total coliform numbers (log10 cfu/g) in the feces between treatments (P = 0.832). There were differences (P < 0.02) in ruminal coliform counts (log10 cfu/mL) between treatments (4.1, 4.3 and 5.0 log10/mL contents in TC, T3 and T9 Treatments, respectively) which tended to increase from the beginning of treatment until the 5th day of treatment (P < 0.05). Overall, we did not obtain the expected results with oral administration of sodium chloride at the applied doses. By comparing the trends in coliform populations in the rumen contents in all treatments, there was an increase over the days. The opposite trend occurred in the feces, due mainly to differences among rumen contents and feces in ewes administered the T9 treatment (P = 0.06). These results suggest that the low chlorate doses used here were suboptimal for the control of coliforms in the gastrointestinal tract of ewes.

Effect of intravenous or oral sodium chlorate administration on the fecal shedding of Escherichia coli in sheep

The effect of gavage or intravenous (i.v.) administration of sodium chlorate salts on the fecal shedding of generic Escherichia coli in wether lambs was studied. To this end, 9 lambs (27 ± 2.5 kg) were administered 150 mg NaClO3/kg BW by gavage or i.v. infusion in a crossover design with saline-dosed controls. The crossover design allowed each animal to receive each treatment during 1 of 3 trial periods, resulting in 9 observations for each treatment. Immediately before and subsequent to dosing, jugular blood and rectal fecal samples were collected at 4, 8, 16, 24, and 36 h. Endpoints measured were fecal generic E. coli concentrations, blood packed cell volume (PCV), blood methemoglobin concentration, and serum and fecal sodium chlorate concentrations. Sodium chlorate had no effects (P > 0.05) on blood PVC or methemoglobin. Fecal generic E. coli concentrations were decreased (P < 0.05) approximately 2 log units (99%) relative to controls 16 and 24 h after sodium chlorate infusion and 24 h after sodium chlorate gavage. Within and across time and treatment, fecal chlorate concentrations were highly variable for both gavage and i.v. lambs. Average fecal sodium chlorate concentrations never exceeded 100 µg/g and were typically less than 60 µg/g from 4 to 24 h after dosing. Times of maximal average fecal sodium chlorate concentration did not correspond with times of lowered average generic E. coli concentrations. Within route of administration, serum sodium chlorate concentrations were greatest (P < 0.01) 4 h after dosing; at the same time point, serum chlorate was greater (P< 0.01) in i.v.-dosed lambs than gavaged lambs but not at 16 or 24 h (P > 0.05). At 8 h, serum chlorate concentrations of gavaged lambs were greater (P < 0.05) than in i.v.-dosed lambs. Serum chlorate data are consistent with earlier studies indicating very rapid transfer of orally dosed chlorate to systemic circulation, and fecal chlorate data are consistent with earlier data showing the excretion of low to marginal concentrations of sodium chlorate in orally dosed animals. Efficacy of sodium chlorate at reducing fecal E. coli concentrations after i.v. infusion suggests that low concentrations of chlorate in gastrointestinal contents, delivered by biliary excretion, intestinal cell sloughing, or simple diffusion, are effective at reducing fecal E. coli levels. Alternatively, chlorate could be eliciting systemic effects that influence fecal E. coli populations.

Effects of short-term sodium chlorate exposure on pigs

The present study evaluated the effects of exposure to different doses of sodium chlorate in 10-week-old pigs. Twenty pigs were divided into four equal groups and treated with different doses of sodium chlorate: 0, 125, 250 and 500 mg kg-1 body weight per day via the drinking water for 7 consecutive days. The results showed a significant decrease (P < 0.05) in red blood cell and white blood cell counts, packed cell volume, haemoglobin, blood urea nitrogen (P < 0.001) and creatinine levels, and an increase in aspartate aminotransferase and alanine aminotransferase (P < 0.05) activities in swine administered sodium chlorate at a dose of 500 mg kg-1 body weight per day. The histopathological study revealed increased numbers of vacuoles in the convoluted tubules, tubular necrosis and degeneration of the renal tubular epithelial cells, depletion of nuclei and lobular necrosis of the liver in all pigs treated with sodium chlorate at 500 mg kg-1 body weight per day. Thus, 7-day administration of sodium chlorate at 500 mg kg-1 body weight per day to pigs affects the liver and kidney tissues as well as the haematologic and serum biochemical parameters.

Sodium chlorate reduces the presence of Escherichia coli in feces of lambs and ewes managed in shed-lambing systems

Our objective was to establish doses of orally administered NaClO(3) that reduced the presence of generic Escherichia coli in intestines of ewes and neonatal lambs managed in a shed-lambing system. Neonatal lambs (n = 32; age = 7.1 ± 1.2 d; BW = 6.8 ± 1.0 kg) and yearling ewes (n = 44; BW = 74.8 ± 5.6 kg) were used in 2 experiments. In both experiments, lambs and ewes were randomly assigned to 1 of 4 groups, and groups were randomly assigned to 1 of 4 treatments. In Exp. 1, neonatal lambs were given single, aqueous, oral doses of saline (control; NaCl, 30 mg·kg of BW(-1)) or 30, 60, or 90 mg of NaClO(3)·kg(-1) of BW. At 25.9 ± 1.3 h after treatment, lambs were euthanized, and intestinal contents were collected aseptically. In Exp. 2, ewes were given single, aqueous, oral doses of saline (NaCl, 150 mg·kg of BW(-1)) or 150, 300, or 450 mg of NaClO(3)·kg(-1) of BW. At 24.0 ± 0.8 h after treatment, fecal samples were collected aseptically from the rectum of each ewe. For both experiments, generic E. coli were enumerated from intestinal contents and feces within 4 to 12 h after collection. In Exp. 1, the effect (P = 0.08) of NaClO(3) on the presence of generic E. coli in colon contents was dose-dependent. This effect was linear (P < 0.01) and negative, which indicated that as NaClO(3) dose increased, generic E. coli that could be isolated from colon contents decreased. Specifically, lambs dosed with 60 and 90 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of content than control lambs (P < 0.06). Lambs dosed with 90 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of content than lambs dosed with 30 mg of NaClO(3)·kg(-1) of BW (P = 0.09). Sodium chlorate dose did not influence (P = 0.58) the presence of generic E. coli in contents collected from the cecum. In Exp. 2, the effect (P < 0.0001) of NaClO(3) on the presence of E. coli in fecal contents from ewes was dose-dependent. This effect was quadratic (P < 0.0001) and negative; ewes dosed with 150, 300, and 450 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of feces than control ewes. No differences in E. coli cfu·g(-1) of feces were detected between NaClO(3) treatments (P = 0.88 to 0.97). Based on these results, a single oral dose of at least 60 and 150 mg of NaClO(3)·kg(-1) of BW in neonatal lambs and yearling ewes, respectively, significantly decreased the presence of generic E. coli in contents from the lower intestine.

Chlorate analyses in matrices of animal origin

Sodium chlorate is being developed as a potential food-safety tool for use in the livestock industry because of its effectiveness in decreasing concentrations of certain Gram-negative pathogens in the gastrointestinal tracts of food animals. A number of studies with sodium chlorate in animals have demonstrated that concentrations of chlorate in meat, milk, wastes, and gastrointestinal contents range from parts per billion to parts per thousand, depending upon chlorate dose, matrix, and time lapse after dosing. Although a number of analytical methods exist for chlorate salts, very few were developed for use in animal-derived matrices, and none have anticipated the range of chlorate concentrations that have been observed in animal wastes and products. To meet the analytical needs of this development work, LC-MS, ion chromatographic, and colorimetric methods were developed to measure chlorate residues in a variety of matrices. The LC-MS method utilizes a Cl(18)O(3)(-) internal standard, is applicable to a variety of matrices, and provides quantitative assessment of samples from 0.050 to 2.5 ppm. Due to ion suppression, matrix-matched standard curves are appropriate when using LC-MS to measure chlorate in animal-derived matrices. A colorimetric assay based on the acid-catalyzed oxidation of o-tolidine proved valuable for measuring ≥20 ppm quantities of chlorate in blood serum and milk, but not urine, samples. Ion chromatography was useful for measuring chlorate residues in urine and in feces when chlorate concentrations exceeded 100 ppm, but no effort was made to maximize ion chromatographic sensitivity. Collectively, these methods offer the utility of measuring chlorate in a variety of animal-derived matrices over a wide range of chlorate concentrations.

Fate of chlorate present in cattle wastes and its impact on Salmonella Typhimurium and Escherichia coli O157:H7

Chlorate salts are being developed as a feed additive to reduce the numbers of pathogens in feedlot cattle. A series of studies was conducted to determine whether chlorate, at concentrations expected to be excreted in urine of dosed cattle, would also reduce the populations of pathogens in cattle wastes (a mixture of urine and feces) and to determine the fate of chlorate in cattle wastes. Chlorate salts present in a urine-manure-soil mixture at 0, 17, 33, and 67 ppm had no significant effect on the rates of Escherichia coli O157:H7 or Salmonella Typhimurium inactivation from batch cultures. Chlorate was rapidly degraded when incubated at 20 and 30 degrees C with half-lives of 0.1 to 4 days. Chlorate degradation in batch cultures was slowest at 5 degrees C with half-lives of 2.9 to 30 days. The half-life of 100 ppm chlorate in an artificial lagoon system charged with slurry from a feedlot lagoon was 88 h. From an environmental standpoint, chlorate use in feedlot cattle would likely have minimal impacts because any chlorate that escaped degradation on the feedlot floor would be degraded in lagoon systems. Collectively, these results suggest that chlorate administered to cattle and excreted in wastes would have no significant secondary effects on pathogens present in mixed wastes on pen floors. Lack of chlorate efficacy was likely due to low chlorate concentrations in mixed wastes relative to chlorate levels shown to be active in live animals, and the rapid degradation of chlorate to chloride at temperatures of 20 degrees C and above.

Nutrition-based health in animal production

Events such as BSE, foot and mouth disease and avian influenza illustrate the importance of animal health on a global basis. The only practical solution to deal with such problems has usually been mass culling of millions of animals at great effort and expense. Serious consideration needs to be given to nutrition as a practical solution for health maintenance and disease avoidance of animals raised for food. Health or disease derives from a triad of interacting factors; diet–disease agent, diet–host and disease agent–host. Various nutrients and other bioactive feed ingredients, nutricines, directly influence health by inhibiting growth of pathogens or by modulating pathogen virulence. It is possible to transform plant-based feed ingredients to produce vaccines against important diseases and these could be fed directly to animals. Nutrients and nutricines contribute to three major factors important in the diet–host interaction; maintenance of gastrointestinal integrity, support of the immune system and the modulation of oxidative stress. Nutrition-based health is the next challenge in modern animal production and will be important to maintain economic viability and also to satisfy consumer demands in terms of food quality, safety and price. This must be accomplished largely through nutritional strategies making optimum use of both nutrients and nutricines.

Pre-harvest Interventions to Reduce the Shedding of E. coli O157 in the Faeces of Weaned Domestic Ruminants: A Systematic Review

Our objective was to use formal systematic review methods to evaluate the efficacy of interventions to reduce faecal shedding of Escherichia coli O157 in post-weaned ruminants by increasing animal resistance. The methodology consisted of an extensive search to identify all potentially relevant research, screening of titles and abstracts for relevance to the research question, quality assessment of relevant research, extraction of data from research of sufficient quality, and qualitative summarization of results. The interventions evaluated included probiotics, vaccination, antimicrobials, sodium chlorate, bacteriophages and other feed additives. There was evidence of efficacy for the probiotic combination Lactobacillus acidophilus NP51 (NPC 747) and Propionibacterium freudenreichii and for sodium chlorate in feed or water. The effectiveness of vaccination varied among studies and among vaccine protocols and there was no consistent evidence to suggest that antibiotic use was associated with a decrease in faecal shedding of E. coli O157, or that current industry uses of antimicrobials were associated with increased faecal shedding. There were an insufficient number of studies available to address the effectiveness of bacteriophages and several other feed additives. In general, few of the primary studies evaluated the interventions under commercial housing conditions with a natural disease challenge, there were inconsistencies in the results among study designs and in some cases among studies within study designs, and a relatively large proportion of publications were excluded based on quality assessment criteria. Few studies reported on associations between the proposed intervention and production parameters, such as average daily gain and feed: gain ratio. While the results suggest that some interventions may be efficacious, there are knowledge gaps in our understanding of the efficacy of pre-harvest interventions to increase animal resistance to E. coli O157 that require further targeted research.

HPLC determination of chlorate metabolism in bovine ruminal fluid

Salmonella and Escherichia coli are two bacteria that are important causes of human and animal disease worldwide. Chlorate is converted in the cell to chlorite, which is lethal to these bacteria. An HPLC procedure was developed for the rapid analysis of chlorate (ClO(3)(-)), nitrate (NO(3)(-)), and nitrite (NO(2)(-)) ions in bovine ruminal fluid samples. Standard curves for chlorite, nitrite, nitrate, and chlorate were well defined linear curves with R(2) values of 0.99846, 0.99106, 0.99854, and 0.99138, respectively. Concentrations of chlorite could not be accurately determined in bovine ruminal fluid because chlorite reacts with or binds a component(s) or is reduced to chloride in bovine ruminal fluid resulting in low chlorite measurements. A standard curve ranging from 25 to 150 ppm ClO(3)(-) ion was used to measure chlorate fortified into ruminal fluid. The concentration of chlorate was more rapidly lowered (P < 0.01) under anaerobic compared to aerobic incubation conditions. Chlorate alone or chlorate supplemented with the reductants sodium lactate or glycerol were bactericidal in anaerobic incubations. In anaerobic culture, the addition of sodium formate to chlorate-fortified ruminal fluid appeared to decrease chlorate concentrations; however, formate also appeared to moderate the bactericidal effect of chlorate against E. coli. Addition of the reductants, glycerol or lactate, to chlorate-fortified ruminal fluid did not increase the killing of E. coli at 24 h, but may be useful when the reducing equivalents are limiting as in waste holding reservoirs or composting systems required for intense animal production.

Effects of nitrate or nitro supplementation, with or without added chlorate, on Salmonella enterica serovar Typhimurium and Escherichia coli in swine feces

The effects of coincubating the active agent of an experimental chlorate product with nitrate or select nitro compounds, possible inducers and competing substrates for the targeted respiratory nitrate reductase, on concentrations of experimentally inoculated Salmonella enterica serovar Typhimurium and indigenous Escherichia coli were determined. Studies were completed in swine fecal suspensions as a prelude to the administration of these inhibitors to pigs. Results confirmed the bactericidal effect of chlorate (5 to 10 mM) against these fecal enterobacteria, reducing (P < 0.05) concentrations by > 2 log CFU ml(-1) after 3 to 6 h of incubation. An effect (P < 0.05) of pH was observed, with considerable regrowth of Salmonella and E. coli occurring after 24 h of incubation in suspensions buffered to pH 7.1 but not in suspensions buffered to pH 6.5 or 5.6. A 24-h coincubation of fecal suspensions with 5 to 10 mM chlorate and as little as 2.5 mM nitrate or 10 to 20 mM 2-nitro-1-propanol, 2-nitroethanol, and, sometimes, nitroethane decreased (P < 0.05) Salmonella but not necessarily E. coli concentrations. 2-Nitro-1-propanol and 2-nitroethanol exhibited inhibitory activity against Salmonella and E. coli by an undetermined mechanism, even in the absence of added chlorate.

Zoonotic bacterial populations, gut fermentation characteristics and methane production in feedlot steers during oral nitroethane treatment and after the feeding of an experimental chlorate product

Nitroethane inhibits the growth of certain zoonotic pathogens such as Campylobacter and Salmonella spp., foodborne pathogens estimated to cause millions of human infections each year, and enhances the Salmonella- and Escherichia coli-killing effect of an experimental chlorate product being developed as a feed additive to kill these bacteria immediately pre-harvest. Limited studies have shown that nitroethane inhibits ruminal methane production, which represents a loss of 2-12% of the host's gross energy intake and contributes to global warming and destruction of the ozone layer. The present study was conducted to assess the effects of 14-day oral nitroethane administration, 0 (0X), 80 (1X) or 160 (2X)mg nitroethane/kg body weight per day on ruminal and fecal E. coli and Campylobacter, ruminal and fecal methane-producing and nitroethane-reducing activity, whole animal methane emissions, and ruminal and fecal fermentation balance in Holstein steers (n=6 per treatment) averaging 403+/-26 (SD) kg BW. An experimental chlorate product was fed the day following the last nitroethane administration to determine effects on E. coli and Campylobacter. The experimental chlorate product decreased (P<0.001) fecal, but not ruminal (P>0.05) E. coli concentrations by 1000- and 10-fold by 24 and 48 h, respectively, after chlorate feeding when compared to pre-treatment concentrations (>5.7 log(10) colony forming units/g). No effects (P>0.05) of nitroethane or the experimental chlorate product were observed on fecal Campylobacter concentrations; Campylobacter were not recovered from ruminal contents. Nitroethane treatment decreased (P<0.01) ruminal (8.46, 7.91 and 4.74+/-0.78 micromol/g/h) and fecal (3.90, 1.36 and 1.38+/-0.50 micromol/g/h) methane-producing activity for treatments 0X, 1X and 2X, respectively. Administration of nitroethane increased (P<0.001) nitroethane-reducing activity in ruminal, but not fecal samples. Day of study affected ruminal (P<0.0001) but not fecal (P>0.05) methane-producing and nitroethane-reducing activities (P<0.01); treatment by day interactions were not observed (P>0.05). Ruminal accumulations of acetate decreased (P<0.05) in 2X-treated steers when compared with 0X- and 1X-treated steers, but no effect (P>0.05) of nitroethane was observed on propionate, butyrate or the acetate to propionate ratio. Whole animal methane emissions, expressed as L/day or as a proportion of gross energy intake (%GEI), were unaffected by nitroethane treatment (P>0.05), and were not correlated (P>0.05) with ruminal methane-producing activity. These results demonstrate that oral nitroethane administration reduces ruminal methane-producing activity but suggest that a microbial adaptation, likely due to an in situ enrichment of ruminal nitroethane-reducing bacteria, may cause depletion of nitroethane, at least at the 1X administration dose, to concentrations too low to be effective. Further research is warranted to determine if the optimization of dosage of nitroethane or related nitrocompouds can maintain the enteropathogen control and anti-methanogen effect in fed steers.

The Effect of an Experimental Chlorate Product on Salmonella Recovery of Turkeys when Administered Prior to Feed and Water Withdrawal

Previously, an experimental chlorate product (ECP) has been observed to reduce Escherichia coli and Salmonella infections in swine, cattle, and broilers. The following studies were performed to investigate the effects of different concentrations and durations of administering ECP on crop and ceca Salmonella typhimurium (ST) colonization of turkeys. In 2 separate trials, each conducted with 2 replicates, 15-wk-old turkey toms were challenged with 10(7) to 10(9) cfu of ST. In Experiment 1, toms were administered 0, 0.5, 1.0, 2.0, or 4.0x of ECP (a 1.0x concentration is equivalent to a 15 mM chlorate ion concentration) in the drinking water for 38 h. In Experiment 2, toms were administered a 2x concentration of ECP in the drinking water for 0, 14, 26, or 38 h prior to water withdrawal. All treatments were followed by a 10-h water withdrawal and an 8-h feed withdrawal prior to organ sampling. In Experiment 1, turkeys provided ECP had significantly (P < 0.05) lower populations and incidences of crop (>1.4 log reduction) and ceca (>0.6 log reduction) ST as compared with control birds (2.1 and 0.94 log ST average for all trials, respectively), with little or no additional benefit from administration of higher ECP concentrations. In Experiment 2, toms provided ECP had lower populations of crop (>2.2 log reduction) and ceca (>1.5 log reduction) ST when compared with controls (3.1 and 1.8 log ST, respectively). Again, there appeared to be little benefit in longer administration intervals on quantitative reduction of ST. These experiments suggest that the ECP significantly reduces Salmonella colonization in commercial turkeys when administered prior to feed and water withdrawal.

Evaluation of Salmonella enteritidis in molting hens after administration of an experimental chlorate product (for nine days) in the drinking water and feeding an alfalfa molt diet

The method most commonly used to induce molting and stimulate multiple egg-laying cycles in laying hens for commercial egg production is to fast the hens. Unfortunately, increased risk of Salmonella enteritidis (SE) infection may result from the use of this method. Methods to stimulate multiple egg-laying cycles without increasing the risk of SE infection are needed. Hens over 50 wk of age were divided into 12 groups of 11 hens each and placed in individual laying cages. One week prior to dietary changes, hens were placed on an 8-h light and 16-h dark photoperiod that continued for the 9-d molt. All hens were challenged orally with 10(6) cfu of SE on the fourth day of the molt. Treatments were nonfed hens with distilled water (NFD), nonfed hens with the experimental chlorate product (ECP, which provided 15 mM chlorate ion) water (NFECP), alfalfa diets with distilled water (ALD), and alfalfa diets with ECP water (ALECP). In the NFD hens, 67% (log10 2.74) of the crops and 94% (log10 5.62) of the ceca were colonized, whereas for the NFECP hens significant reductions to 22% (log10 1.05) of the crops and 61% (log10 2.44) of the ceca were observed. In the ALD hens, 61% (log10 2.52) of the crops and 94% (log10 4.06) of the ceca were colonized. In the ALECP hens, highly significant reductions to 11% (log10 1.26) of the crops and 39% (log10 1.12) of the ceca were observed. When compared with the NFD hens, significant reductions in SE invasion of the ovary, liver, and spleen occurred in all other treatments, except the ovary in the ALD hens. The low alfalfa intake is probably a factor in our lowered protection against SE when compared with previous results. For several parameters, these results suggest that ECP or the combination of ECP and alfalfa may be a useful tool to reduce the risk of SE during an induced molt.

Novel preharvest strategies involving the use of experimental chlorate preparations and nitro-based compounds to prevent colonization of food-producing animals by foodborne pathogens

Foodborne diseases caused by enterohemorrhagic Escherichia coli, Salmonella, and Campylobacter species are of public health and economic significance. Shedding of these pathogens during production and slaughter are risks for contamination of products for human consumption. Consequently, strategies are sought to prevent or reduce the carriage of these pathogens in food animals before slaughter. Experimental products containing chlorate salts have been proven efficacious in reducing concentrations of E. coli and Salmonella Typhimurium in the gut of cattle, sheep, swine, and poultry when administered as feed or water additives. Mechanistically, chlorate selectively targets bacteria expressing respiratory nitrate reductase activity, such as most members of the family Enterobacteriaceae, as this enzyme catalyzes the reduction of chlorate to lethal chlorite. Most beneficial gut bacteria lack respiratory nitrate reductase activity, and thus the technology appears compatible with many bacteria exhibiting competitive exclusion capabilities. More recently, select nitrocompounds have been investigated as potential feed additives, and although these nitrocompounds significantly reduce pathogens on their own, evidence indicates that they may most effectively be used to complement the bactericidal activity of chlorate. A particularly attractive aspect of the nitrocompound technology is that, as potent inhibitors of ruminal methanogenesis, they may allow producers the opportunity to recoup costs associated with their use. At present, neither chlorate nor the nitrocompounds have been approved as feed additives by the US Food and Drug Administration, and consequently they are not yet available for commercial use.

The Shiga toxin-producing Escherichia coli, their ruminant hosts, and potential on-farm interventions: a review

The emergence of Shiga toxin-producing Escherichia coli serotype O157:H7 as a major human pathogen over the last 2 decades has focused attention on this organism’s ruminant hosts. Despite implementation of conventional control methods, people continue to become seriously ill from contaminated meat or other food products, manure-contaminated drinking and recreational water, and direct contact with ruminants. E. coli O157:H7 can cause life-threatening disease, and is a particular threat to children, through acute and chronic kidney damage. Compared with other food-borne bacteria, E. coli O157:H7 has a remarkably low infectious dose and is environmentally robust. Cattle are largely unaffected by this organism and have been identified as the major source of E. coli O157:H7 entering the human food chain. Other Shiga toxin-producing E. coli can be pathogenic to humans and there is increasing evidence that their significance has been underestimated. Governments around the world have acted to tighten food safety regulations, and to investigate animal sources and on-farm control of this and related organisms. Potential intervention strategies on-farm include: feed and water hygiene, altered feeding regimes, specific E. coli vaccines, antibacterials, antibiotics, probiotics, and biological agents or products such as bacteriophages, bacteriocins, or colicins.

Utilization of the nitrate reductase enzymatic pathway to reduce enteric pathogens in chickens

Previous reports have shown that some bacteria, including Salmonella, use a dissimilatory nitrate reductase enzyme pathway (NREP) in anaerobic environments. This enzyme reduces nitrate to nitrite and has been shown to cometabolize chlorate to cytotoxic chlorite. The present investigations were performed to evaluate the susceptibility of a competitive exclusion culture (CE) to the experimental chlorate product (ECP). A commercially available CE product was evaluated for its nitrate reductase activity and therefore its chlorate sensitivity. Individual isolates (in triplicate) were cultured in 10 mL of Viande Levure broth containing 5 mM sodium nitrate or 10 mM sodium chlorate. Bacterial growth (optical density at 625 nm) was measured and 1-mL aliquots were removed concurrently for colorimetric determination of nitrate content at 0, 3, 6, and 24 h. Of the 15 different facultative strains, 11 had slight NREP utilization, 3 had moderate NREP utilization, and the remainder were NREP negative (with slight and moderate NREP utilization: >0.1 to <1.0 mM and >1.0 mM nitrate used within 6 h, respectively). Of the obligate anaerobes evaluated, 3 had slight NREP utilization and the remainder were NREP negative. In vivo studies utilizing both products (CE and ECP) in a horizontal transmission challenge model (seeders + contacts) showed significant reductions in Salmonella from 5.37 to 1.76 log10 cfu/g and 3.94 to 0.07 log10 cfu/g, respectively. The combined effect of the CE culture and an ECP are effective in killing these food-borne pathogens.