Transcriptional analysis reveals specific niche factors and response to environmental stresses of enterohemorrhagic Escherichia coli O157:H7 in bovine digestive contents

Background Enterohemorrhagic Escherichia coli (EHEC) are responsible for severe diseases in humans, and the ruminant digestive tract is considered as their main reservoir. Their excretion in bovine feces leads to the contamination of foods and the environment. Thus, providing knowledge of processes used by EHEC to survive and/or develop all along the bovine gut represents a major step for strategies implementation. Results We compared the transcriptome of the reference EHEC strain EDL933 incubated in vitro in triplicate samples in sterile bovine rumen, small intestine and rectum contents with that of the strain grown in an artificial medium using RNA-sequencing (RNA-seq), focusing on genes involved in stress response, adhesion systems including the LEE, iron uptake, motility and chemotaxis. We also compared expression of these genes in one digestive content relative to the others. In addition, we quantified short chain fatty acids and metal ions present in the three digestive contents. RNA-seq data first highlighted response of EHEC EDL933 to unfavorable physiochemical conditions encountered during its transit through the bovine gut lumen. Seventy-eight genes involved in stress responses including drug export, oxidative stress and acid resistance/pH adaptation were over-expressed in all the digestive contents compared with artificial medium. However, differences in stress fitness gene expression were observed depending on the digestive segment, suggesting that these differences were due to distinct physiochemical conditions in the bovine digestive contents. EHEC activated genes encoding three toxin/antitoxin systems in rumen content and many gene clusters involved in motility and chemotaxis in rectum contents. Genes involved in iron uptake and utilization were mostly down-regulated in all digestive contents compared with artificial medium, but feo genes were over-expressed in rumen and small intestine compared with rectum. The five LEE operons were more expressed in rectum than in rumen content, and LEE1 was also more expressed in rectum than in small intestine content. Conclusion Our results highlight various strategies that EHEC may implement to survive in the gastrointestinal environment of cattle. These data could also help defining new targets to limit EHEC O157:H7 carriage and shedding by cattle.

Metals Accumulation in Muscle Tissues and Digestive Contents of Periglypta reticulata (Kerang Geton) from Lancang Island, Jakarta

The concentration of nineteen metals (Hg, As, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Mo, Ni, Pb, Se, Sr, Ti, Tl, V, and Zn) were determined in muscle tissues and digestive contents of Periglypta reticulata (Kerang Geton), collected from Lancang Island part of Seribu Islands, Jakarta. An interaction between toxic and essential metal in a clam is also studied. The results showed high concentrations of As (4.56), V (1.20), and Zn (4.91) mg/kg wet weight in muscle tissues and As (7.16), Ti (2.53), and Zn (8.68) mg/kg wet weight in digestive contents. Average concentrations of metals in muscle tissues and digestive contents were below regulation limit from permissible standard National Agency of Drug and Food Control except for Arsenic (As). The average concentration of metals in muscle tissues was significantly (P < 0.05) lower than in digestive contents except As, Co, Cr, Mg, and Tl, respectively. Toxic metals (Pb, Hg, Cd, and As) showed a strong correlation with several essential metals so that these metals can be a threat to the main function of a particular metal. The present study showed digestive contents could accumulate in higher metals; therefore, we suggested removing it before consuming this clam.

The Effects of Age and Adiposity on the Digestibility of Micellar Casein in Rats

Objectives The aim of this study was to evaluate the digestibility of casein and its amino acids (AA) in rats of different ages (2 months vs 11 months) and adiposity levels (normal vs high). Methods Wistar rats of 1 month (n = 15) and 10 months (n = 15) at their arrival were fed ad libitum for 28 days either with a standard diet (14% P/E, 75% C/E, 11% L/E) or a Western diet (14% P/E, 51% C/E, 35% L/E) in order to obtain respectively rats of normal and high adiposity levels. Four groups were constituted (n = 7/8): 2 months/normal adiposity (2 M/NA), 2 months/high adiposity (2 M/HA), 11 months/normal adiposity (11 M/NA) and 11 months/high adiposity (11 M/HA). After a week on the standard diet, the rats consumed a 4 g meal containing 15N labeled casein (Prodiet® 85B). Blood samples were taken at t = 0, t = 1 h, t = 3 h after meal consumption, and the rats were euthanized at t = 6 h. Digestive contents were collected and body composition was determined. Nitrogen quantity and 15N enrichment were analyzed in the meal and digestive contents by EA-IRMS, allowing for the estimation of casein digestibility. Concentrations in AA and their 15N enrichments were determined respectively by UHPLC and GC-C-IRMS to obtain the digestibility of individual AA. Results Weight did not differ between groups of the same age, but body composition analysis showed a significant difference in adiposity (P = 0.0008 between the 2 M groups; P = 0.0004 between the 11 M groups). Nitrogen fecal digestibility of casein increased significantly in rats with higher adiposity levels (2 M/NA = 94.1 ± 1.1%; 2 M/HA = 95.2 ± 1.7%; 11 M/NA = 94.5 ± 2.2% for 11 M/HA = 95.9 ± 0.7%; P = 0.0339). No difference was found in the digestibility of individual AA. 6 hours after meal ingestion, there was significantly more exogenous nitrogen in the stomach of rats aged 11 months compared to those of 2 months (3,9 ± 6,9% for the 2 M groups and 11,3 ± 9,2% for the 11 M groups P = 0.0188;). Except for methionine, there was no difference in plasma concentration levels of essential AA over time between the groups. Conclusions Our results suggest that age slows down digestion, in accordance with the literature. We showed that adiposity increased casein digestibility but without any effect at the level of individual AA digestibility. Funding Sources Ingredia.

Temporal and ontogenic variations of diet of the goldblotch grouper Epinephelus costae (Serranidae) in the eastern coast of Algeria

The diet of the goldblotch grouper Epinephelus costae of the eastern coast of Algeria was studied from March 2011 to February 2012. A total of 275 individuals, whose total length varied between 21.1 and 79.79 cm and weight between 103.13 and 5390.00 g, were examined. The index of relative importance (%IRI) combining the three main descriptors of the presence of different ingested prey (%F, %N, %W) was used to characterize the relative importance of different food taxa. Qualitative and quantitative variations in diet were studied according to sexual maturity (immature and mature), sex (male and female), size (small, medium and large) and seasons. The average annual digestive vacuity is 17.82%. It does not vary according to sex, size or maturity, but is different between summer and winter. Qualitative analysis of digestive contents reveals a fairly diverse range of predation with 319 prey counted for a total weight of 934.85 g, which corresponds to an average number (Nm) and weight (Wm) of 1.4 and 4.14 g respectively. This species feeds on benthopelagic prey composed mainly of bony fish (%IRI = 76.16), pancrustacea (%IRI = 16.14) and molluscs (%IRI = 6.24). All other prey were accessory (plants) or accidental (annelids). Significant differences in feeding habits occur according to seasons and fish size.

Alternatives to antibiotic growth promoters for weanling pigs

An experiment was conducted to evaluate the addition of sodium butyrate, plant extracts and nucleotides on weanling pig performance, digestive content pH, organ morphometry, and intestinal epithelial histology. A total of 90 piglets at 21 days of age and an average initial weight of 6.35±0.34kg were used. The piglets were distributed in a randomized complete block design with five treatments, six replicates, and three animals per experimental unit. The treatments consisted of the following: Control: basal diet without antibiotic; Antibiotic: basal diet with 40mg kg-1 colistin sulfate and Additive: 1000, 1500 and 2000mg kg-1 of a combination of sodium butyrate + plant extracts + nucleotides. The experiment lasted 35 days, at which time one animal was slaughtered to assess pH of the digestive contents, morphometry of the organs and histology of the intestinal epithelium. No differences were found (P>0.05) in the performance, pH of the digestive contents, morphometry of the organs or histology of the intestinal epithelium by the analysis of orthogonal polynomials or contrasts. The combination of sodium butyrate, plant extracts and nucleotides not improved the productive characteristics of weanling pigs.

Diagnose of the ingestion of Asclepias mellodora St. Hil. by sheep through microhistological analysis of their digestive contents

Asclepias mellodora St. Hil. is a native acute toxic species frequent in the grasslands of the Buenos Aires province, Argentina, whose toxicity had not been assessed until now. This study evaluates the minimal lethal dose of this species for sheep, and the possibility of microscopically recognizing its fragments in gastrointestinal contents as a complementary diagnostic tool in necropsies. Three Frisona sheep (average LW=55±4.5 kg) were dosed via an esophageal tube with each one of the following doses of asclepias: 8.0, 5.0, 2.0 and 0.8 g DM.kg LW-1. Sheep poisoned with the three higher doses died between 10 and 85 h after intoxication, but those receiving the lower dose did not. During necropsies we: 1) determined the dry weight of the contents of rumen+reticulum, omasum+abomasum, and large intestine, 2) estimated the percentages of asclepias fragments by microanalysis correcting for digestion effects on fragment recognition, and 3) calculated the total mass of asclepias in the digestive tract of each animal. For the three higher doses, the mass of asclepias identified in the total ingesta was 12.3±3.4% of the amount supplied, possibly because of the strong diarrhea its ingestion produced. The percentages of asclepias in rumen+reticulum did not differ from the average quantified for the entire tract. The results of this study indicate that the minimal lethal doses of asclepias for sheep is between 2.0 and 0.8g DM·kg LW-1, and that the microhistological analysis of the rumen+reticulum, the easiest region to sample, can be used to confirm the ingestion of this toxic species, although the estimated percentage will be not a good estimator of the ingested percentage.

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 acid-sensitive 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.