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1.
Three 3-month-old Japanese Black calves were experimentally infected with Escherichia coli O157:H7 to define the magnitude (CFU/g) and duration of fecal shedding of the organism. In two of the three calves, fecal shedding of E. coli O157:H7 ceased in 5 and 9 weeks. The remaining calf continued shedding E. coli O157:H7 for more than 31 weeks, and the magnitude of the shedding ranged from 10(1) to 10(4) CFU/g of feces. The possibility is suggested that a percentage of animals naturally infected with E. coli O157:H7 on farms may become long-term shedders, transmitting the organism to other animals in the herd and to the proximate environment.  相似文献   

2.
To assess the duration of fecal shedding upon initial infection, the duration of shedding after subsequent re-infection and the effects of dietary restriction and antibiotic treatment on shedding recrudescence, four, one-week-old calves were orally inoculated on three separate occasions with 5x10(8) cfu of Escherichia coli O157:H7 strain 86-24 Nal-R. Fecal shedding was followed by serial culture three times weekly. Following the first inoculation, the calves shed E. coli O157:H7 in their feces for a mean of 30 days, with a range of 20 to 43 days. Following the second and third inoculations, the calves shed E. coli O157:H7 in their feces for 3-8 days. In each of the three inoculations, feed was withheld from the calves for 24 h after they had become fecal culture negative. Two calves resumed shedding, one for 1 day and the other for 4 days, after food was withheld after the third inoculation, but not in the first two inoculations. In the third inoculation, one calf resumed shedding for one day after treatment with oxytetracycline. No E. coli O157:H7 strain 86-24 Nal-R was found in the calves at necropsy. These calves did not exhibit persistent low-level shedding, and did not appear to be persistently colonized with E. coli O157:H7.  相似文献   

3.
The objective of this study was to compare the concentration and duration of fecal shedding of Escherichia coli O157:H7 between calves fed milk replacer with or without antibiotic (oxytetracycline and neomycin) supplementation. Eighteen 1-wk-old Holstein calves were orally inoculated with a strain of E. coli O157:H7 (3.6 x 10(8) cfu/calf) made resistant to nalidixic acid (NA). Rectal samples were obtained three times weekly for 8 wk following oral inoculation. Fecal shedding of NA-resistant E. coli O157:H7 was quantified by direct plating or detected by selective enrichment procedure. Eight weeks after inoculation, calves were killed, necropsied, and tissues (tonsils, retropharyngeal and mesenteric lymph nodes, and Peyer's patches) and gut contents (rumen, omasum, abomasum, ileum, cecum, colon, and rectum) were sampled to quantify or detect NA-resistant E. coli O157:H7. The percentage of calves shedding NA-resistant E. coli O157:H7 in the feces in the antibiotic-fed group was higher (P < 0.001) early in the study period (d 6 and 10) compared with the control group fed no antibiotics. There was no difference between treatment and control groups in the concentration of E. coli O157 in feces that were positive at quantifiable concentrations. A comparison of the duration of fecal shedding between treated and untreated calves showed no significant difference between groups. At necropsy, E. coli O157:H7 was recovered from the rumen and omasum of one calf in the control group and from retropharyngeal lymph node and Peyer's patch of two calves in the antibiotic group. Supplementation of milk replacer with antibiotics may increase the probability of E. coli O157:H7 shedding in dairy calves, but the effect seems to be of low magnitude and short duration.  相似文献   

4.
Grazing-fed cattle were previously demonstrated to be reservoir of non-O157 Shigatoxigenic Escherichia coli (STEC) serotypes in Argentina. The acid-resistance of some STEC strains makes it reasonable to assume the presence in feedlot of particular STEC serotypes. Fifty-nine animals were sampled every 2 weeks during 6 months by rectal swabs. Twenty-seven of 59 animals (45.8%) were shown to be Stx2(+); 3/59 (5.1%) carried Stx1(+) and 7/59 (11.9%) were Stx1(+) Stx2(+). Among 44 STEC isolates, 31 isolates were associated to 10 O serogroups (O2, O15, O25, O103, O145, O146, O157, O171, O174, O175) and 13 were considered non-typable (NT). Six H antigens (H2, H7, H8, H19, H21, H25) were distributed in 21 isolates whereas 23 were non-mobile (H-). Seventeen of 44 strains (38.6%) were eaeA(+) and 14 (31.8%) harbored the 60MDa plasmid. The megaplasmid (Mp) and eaeA gene were simultaneously found in a limited number of serotypes belonging to the enterohaemorrhagic E. coli (EHEC). E. coli O157:H7 strains, isolated from four (6.8%) animals, corresponded to the Stx2(+), eaeA(+), Mp(+) pattern. Three O157:H7 strains belonged to phage type 4 and the other strain was atypical. Many serotypes isolated from grain-fed cattle (O2:H25, O15:H21, O25:H19, O145:H-, O146:H-, O146:H21, O157:H7, O175:H8) also differed from those isolated by us previously from grazing animals. The serotypes O15:H21, O25:H19 and O175:H8 had not been identified at present as belonging to STEC. This work provides new data for the understanding of the ecology of STEC in grain-fed cattle and confirms that cattle are an important reservoir of STEC.  相似文献   

5.
Isolation of Shiga-toxin (Stx) positive Escherichia coli O157:H7 from commercially grown pigs has been reported. Furthermore, experimental infection studies have demonstrated that Stx-positive E. coli O157:H7 can persist in 12-week-old experimentally orally inoculated conventional pigs for up to 2 months and that persistence was not dependent upon intimin. We have shown that the flagellum of Stx-negative E. coli O157:H7 does not have a role to play in pathogenesis in ruminant models whereas, in poultry, the flagellum of E. coli O157:H7 was important for long-term persistent infection. The contribution of the flagellum of Stx-negative E. coli O157 in the colonisation of pigs was investigated by adherence assays on a porcine (IPI-21) cell line, porcine in vitro organ culture (IVOC) and experimental oral inoculation of conventional 14-week-old pigs. E. coli O157:H7 NCTC12900nal(r) and isogenic aflagellate and intimin deficient mutants adhered equally well to IPI-21 cells. In porcine IVOC association assays, E. coli O157:H7 NCTC12900nal(r) was associated in significantly higher numbers to tissues from the caecum and the terminal rectum than other sites. The aflagellate and intimin deficient mutants significantly adhered in greater numbers to more IVOC gastrointestinal tissues than the parent. Groups of 14-week-old pigs were dosed orally with 10(10)CFU/10ml of either E. coli O157:H7 NCTC12900nal(r) or isogenic aflagellate and intimin deficient mutants and recovery of each test strain was similar. Histological analysis of pig tissues at post mortem examination revealed that E. coli O157 specifically stained bacteria were associated with the mucosa of the ascending and spiral colon. These data suggest that colonisation and persistence of Stx-negative E. coli O157:H7 in pigs, involves mechanisms that do not require the flagellum or intimin.  相似文献   

6.
Inclusion of distillers grains (DG) in cattle diets has been shown to increase fecal shedding of Escherichia coli O157:H7. It is hypothesized that altered gut fermentation by DG may be responsible for the positive association. Therefore, feed additives affecting ruminal or hindgut fermentation of DG also may affect fecal shedding of E. coli O157:H7. The objectives of the study were to evaluate effects of monensin (33 or 44 mg/kg of DM), supplemental urea (0, 0.35, or 0.70% of DM), and ractopamine (0 or 200 mg/steer daily administered during the last 42 d of finishing) in a steam-flaked corn grain-based diet containing 30% wet sorghum DG on fecal shedding of E. coli O157:H7. Seven hundred twenty crossbred beef steers, housed in 48 pens (15 steers/pen), were assigned to dietary treatments in a randomized complete block design with a 2 × 3 × 2 factorial treatment arrangement. Fresh pen floor fecal samples (10 per/pen) were collected every 2 wk for 14 wk (July through November) and cultured for E. coli O157:H7. Isolation of E. coli O157:H7 was by selective enrichment of fecal samples in an enrichment broth, immunomagnetic separation, followed by plating onto a selective medium. Samples that yielded sorbitol-negative colonies, which were positive for indole production, O157 antigen agglutination, and contained rfbE, fliC, and stx2 were considered positive for E. coli O157:H7. Fecal prevalence data were analyzed as repeated measures using negative binomial regression to examine effects and interactions of sampling day, urea, monensin, and ractopamine. Mean fecal prevalence of E. coli O157:H7 was 7.6% and ranged from 1.6 to 23.6%. Cattle fed monensin at 44 mg/kg of feed had less (P = 0.05) fecal E. coli O157:H7 prevalence than cattle fed 33 mg/kg (4.3 vs. 6.8%). Although the reason for the reduction is not known, it is likely because of changes in the microbial ecosystem induced by the greater amount of monensin in the hindgut. Supplemental urea at 0.35 or 0.70% had no effect (P = 0.87) on fecal shedding of E. coli O157:H7. Fecal prevalence of E. coli O157:H7 were 5.3, 5.7, and 5.9% for groups fed 0, 0.35, and 0.7% urea, respectively. The inclusion of ractopamine at 0 or 200 mg/(animal?d) had no effect (P = 0.89) on fecal prevalence of E. coli O157:H7 (4.4 vs. 4.0%). Additional research is needed to confirm the reduction in fecal shedding of E. coli O157:H7 in cattle fed monensin at 44 mg/kg of feed compared with cattle fed 33 mg/kg of feed.  相似文献   

7.
The prevalence of Escherichia coli O157:H7 infection in birds is low but several deliberate inoculation studies show that poultry are readily and persistently infected by this organism indicating a possible threat to public health. The mechanisms of colonisation of poultry are not understood and the aim is to establish models to study the interaction of E. coli O157:H7, at the cellular and whole animal levels. A non-toxigenic E. coli O157:H7 (NCTC 12900) was used in adherence assays with an avian epithelial cell line (Div-1) and used to inoculate 1-day-old SPF chicks. In vitro, NCTC 12900 induced micro-colonies associated with cytoskeletal arrangements and pedestal formation with intimate bacterial attachment. In the 1-day-old SPF chick, a dose of 1 x 10(5) cfu resulted in rapid and extensive colonisation of the gastrointestinal tract and transient colonisation of the liver and spleen. The number of E. coli O157:H7 organisms attained approximately 10(8) cfu/ml caecal homogenate 24h after inoculation and approximately 10(7) cfu/ml caecal homogenate was still present at day 92. Faecal shedding persisted for 169 days, ceasing 9 days after the birds came into lay and 6% of eggs were contaminated on the eggshell. Histological analysis of tissue samples from birds dosed with 1x10(7) cfu gave evidence for E. coli O157:H7 NCTC 12900 induced micro-colonies on the caecal mucosa, although evidence for attaching effacing lesions was equivocal. These models may be suitable to study those factors of E. coli O157:H7 that mediate persistent colonisation in avian species.  相似文献   

8.
A longitudinal study was conducted on two dairy farms to investigate the pattern of shedding of verotoxin-producing Escherichia coli (VTEC) in goats. Faecal samples were taken from 20 goat kids once weekly during the first 4 weeks of life and then once every month for the next 5 months of life, and from 18 replacement animals and 15 adults once every month for 12 months. The proportion of samples containing VTEC was higher for replacement animals and adults (85.7% and 78.7%, respectively) than for goat kids (25.4%). About 90% of the VTEC colonies isolated from healthy goats belonged to five serogroups (O33, O76, O126, O146 and O166) but the most frequent serogroups of these isolates, except one, were different in the two herds studied. E. coli O157:H7 was found in three goat kids on only one occasion. None of the VTEC isolates, except the three E. coli O157:H7 isolates, was eae-positive. The patterns of shedding of VTEC in goat kids were variable, but, in contrast, most of the replacement animals and adults were persistent VTEC shedders. Our results show that isolates of VTEC O33, O76, O126, O146 and O166 are adapted for colonising the intestine of goats but that, in contrast, infection with VTEC O157:H7 in goats seems to be transient.  相似文献   

9.
OBJECTIVE: To determine the prevalence of fecal shedding of Escherichia coli O157:H7 in white-tailed deer (Odocoileus virginianus) with access to cattle pastures. DESIGN: Survey study. SAMPLE POPULATION: 212 fecal samples from free ranging white-tailed deer. PROCEDURE: Fresh feces were collected on multiple pastures from 2 farms in north central Kansas between September 1997 and April 1998. Escherichia coli O157:H7 was identified by bacterial culture and DNA-based methods. RESULTS: Escherichia coli O157:H7 was identified in 2.4% (5/212) of white-tailed deer fecal samples. CONCLUSIONS AND CLINICAL RELEVANCE: There is considerable interest in the beef industry in on-farm control of E coli O157:H7 to reduce the risk of this pathogen entering the human food chain. Results of our study suggest that the design of programs for E coli O157:H7 control in domestic livestock on pasture will need to account for fecal shedding in free-ranging deer. In addition, the results have implications for hunters, people consuming venison, and deer-farming enterprises.  相似文献   

10.
The objectives of this study were to investigate the diversity of Escherichia coli O157:H7 isolates obtained over a 3-month period from a cattle feedlot in order to assess the relationship between environmental and faecal isolates and to determine the pattern of transmission of E. coli O157:H7 between groups of cattle. Faecal samples were obtained from cattle housed in four adjacent feedlot pens at monthly intervals, with environmental pen samples collected simultaneously. All E. coli O157:H7 isolates obtained were examined by pulsed field gel electrophoresis (PFGE), polymerase chain reaction (PCR) to detect eaeA, ehxA, stx1 and stx2 genes and antibiotic sensitivity profiling. Ten isolates were subjected to acid shock to imitate conditions in the acidic cattle abomasum and assess the effect on PFGE profiles. E. coli O157:H7 was isolated from 69 faecal samples and 26 environmental samples. All isolates (n=95) carried the genes for eaeA, ehxA and stx2 and were sensitive to all antibiotics tested. The PFGE profiles of all isolates differed by no more than two bands and clustered within 80% similarity following dendrogram analysis. Acid shock had no effect on the subsequent PFGE patterns. A total of 8.7% (6/69) of cattle were shedding E. coli O157:H7 in the first month with faecal shedding increasing to 52% (36/69) by the third month of the study. A single isolate of E. coli O157:H7 may be passed rapidly through cattle pens, with the environment acting as a significant reservoir for transmission. PFGE is a useful tool for tracking the direct and indirect transmission of E. coli O157:H7 isolates on the farm.  相似文献   

11.
Distillers dried grains with solubles (DDGS) are a coproduct of the ethanol industry and are often used as a replacement for grain in livestock production. Feeding corn DDGS to cattle has been linked to increased fecal shedding of Escherichia coli O157:H7, although in Canada, DDGS are often produced from wheat. This study assessed the effects of including 22.5% wheat or corn DDGS (DM basis) into barley-based diets on performance, carcass characteristics, animal health, and fecal E. coli O157:H7 shedding of commercial feedlot cattle. Cattle (n = 6,817) were randomly allocated to 10 pens per treatment group: WDDGS (diets including 22.5% wheat DDGS), CDDGS (diets including 22.5% corn DDGS), or CTRL (barley substituted for DDGS). Freshly voided fecal pats (n = 588) were collected and pooled monthly for fecal pH measurement and screened for naturally occurring E. coli O157:H7 by immunomagnetic separation (IMS) and direct plating (DP). Hide swabs (n = 367) were collected from randomly selected cattle from each pen before slaughter. Pen-floor fecal samples (n = 18) were collected from treatment groups at entry to the feedlot (<14 d on the finishing diet) and after adapting to the finishing diet for ≥14 d, inoculated (10(9) cfu of a 5 strain naldixic acid-resistant E. coli O157:H7 mixture), incubated (20°C) and evaluated weekly (IMS and DP) to assess fecal E. coli O157:H7 persistence. The WDDGS group had 3.0% poorer ADG (P = 0.007), 5.3% poorer G:F (P < 0.001), and a decreased proportion of Canada Quality Grade AAA carcasses (P = 0.022) compared with CTRL cattle. The CDDGS group had a similar ADG (P = 0.06), a decreased proportion of Canada Yield Grade (YG) 1 (P < 0.001), and greater proportions of Canada YG 2 (P = 0.003) and YG 3 (P < 0.001) carcasses compared with the CTRL group. There were no differences among groups in any of the animal health parameters assessed. Inclusion of DDGS in cattle finishing diets had no effect on fecal shedding (P = 0.650) or persistence (P = 0.953) of E. coli O157:H7. However, feces from cattle on starter diets <14 d had longer persistence of E. coli O157:H7 (week) than cattle on finishing diets ≥14 d (P < 0.003). Inclusion of DDGS in feedlot diets depends on commodity pricing relative to that of barley and for WDDGS must also include the risk of feedlot performance and carcass grading disadvantages. Feeding cattle barley based-diets with 22.5% corn or wheat DDGS did not affect fecal shedding of E. coli O157:H7.  相似文献   

12.
In order to evaluate the prevalence of Shiga toxin-producing Escherichia coli (STEC) strains, 197 fecal samples of healthy cattle from 10 dairy farms, four beef farms and one slaughterhouse at Rio de Janeiro State, Brazil, were examined for Shiga toxin (Stx) gene sequences by polymerase chain reaction (PCR). For presumptive isolation of O157:H7 E. coli, the Cefixime-potassium tellurite-sorbitol MacConkey Agar (CT-SMAC) was used. A high occurrence (71%) of Stx was detected, and was more frequently found among dairy cattle (82% vs. 53% in beef cattle), in which no differences were observed regarding the age of the animals. Dot blot hybridization with stx1 and stx2 probes revealed that the predominant STEC type was one that had the genes for both stx1 and stx2 in dairy cattle and one that had only the stx1 gene for beef cattle. Three (1.5%) O157:H7 E. coli strains were isolated from one beef and two dairy animals by the use of CT-SMAC. To our knowledge, this is the first report of O157:H7 isolation in Brazil. A PCR-based STEC detection protocol led to the isolation of STEC in 12 of 16 randomly selected PCR-positive stool samples. A total of 15 STEC strains belonging to 11 serotypes were isolated, and most of them (60%) had both stx1 and stx2 gene sequences. Cytotoxicity assays with HeLa and Vero cells revealed that all strains except two of serotype O157:H7 expressed Stx. The data point to the high prevalence of STEC in our environment and suggest the need for good control strategies for the prevention of contamination of animal products.  相似文献   

13.
OBJECTIVE: To describe the frequency and distribution of Escherichia coli O157:H7 in the feces and environment of cow-calf herds housed on pasture. SAMPLE POPULATION: Fecal and water samples for 10 cow-calf farms in Kansas. PROCEDURE: Fecal and water samples were obtained monthly throughout a 1-year period (3,152 fecal samples from 2,058 cattle; 199 water samples). Escherichia coli O157:H7 in fecal and water samples was determined, using microbial culture. RESULTS: Escherichia coli O157:H7 was detected in 40 of 3,152 (1.3%) fecal samples, and 40 of 2,058 (1.9%) cattle had > or = 1 sample with E coli. Fecal shedding by specific cattle was transient; none of the cattle had E coli in more than 1 sample. Significant differences were not detected in overall prevalence among farms. However, significant differences were detected in prevalence among sample collection dates. Escherichia coli O157:H7 was detected in 3 of 199 (1.5%) water samples. CONCLUSIONS AND CLINICAL RELEVANCE: Implementing control strategies for E coli O157:H7 at all levels of the cattle industry will decrease the risk of this organism entering the human food chain. Devising effective on-farm strategies to control E coli O157:H7 in cow-calf herds will require an understanding of the epidemiologic characteristics of this pathogen.  相似文献   

14.
A strain of Escherichia coli O157:H7 was isolated from goat faeces during a surveillance study on the prevalence of this serotype of E. coli in farm animals in Greece. Three hundred and fifty one faecal samples were collected from goat, sheep and cattle breeding farms in the area of Epirus, Northwestern Greece. The E. coli O157:H7 isolate was nonsorbitol-fermenter, produced only VT2 and showed a beta-glucuronidase positive activity, a rather unusual biochemical feature for the E. coli O157:H7 serotype. No other strain of E. coli O157:H7 was isolated from the faecal samples of the rest farm animals examined, thus the overall prevalence of animal carriage was found to be 0.2%. The findings also indicate that goats can be a reservoir of E. coli O157:H7 and goat milk, dairy products and meat may serve as a vehicle for the pathogen transmission to humans.  相似文献   

15.
We have previously shown that rectally inoculated sheep excrete Escherichia coli O157:H7 during weeks to months without developing a clear antibody response. However, antibodies against this bacterium were observed in naturally infected sheep, which most likely became orally infected. To understand this difference, sheep were orally inoculated with the same Shiga toxin-negative E. coli O157:H7 strain that was used for the rectal inoculation. A primary oral inoculation resulted in shedding of E. coli O157:H7 in the faeces and detection of antibody responses against intimin, EspA and EspB. The antibody titres waned as shedding decreased. A secondary inoculation resulted in longer shedding, even though a booster antibody response occurred. Cellular responses followed a similar pattern as the antibody levels, albeit with a lower secondary response. The presence of antigen-specific antibody-secreting cells indicates involvement of both a systemic response in the spleen and a local immune response in the terminal rectum. These results suggest that E. coli O157:H7 has to pass the small intestine to evoke antibody responses.  相似文献   

16.
Enterohaemorrhagic Escherichia coli O157:H7 are zoonotic pathogens associated with haemorrhagic colitis (HC) and the haemolytic uremic syndrome (HUS). Ruminants are the main reservoir of this organism and most outbreaks of E. coli O157:H7 infections are food borne. Food contamination by ruminant manure has been reported as the primary source of human infection, therefore inhibition of E. coli O157:H7 colonization and shedding in ruminants could control the risk of human exposure to this pathogen. In the present study a vaccine based on the translocon proteins EspA and EspB and the outer membrane adhesion factor intiminγ significantly reduced faecal shedding of E. coli O157:H7 by orally infected sheep. Protection correlates with serum antibody responses to the defined antigens and validates the targeting of these colonization factors. Whereas vaccination has been described in cattle, this is the first study describing a significant decrease in faecal shedding following systemic immunization of sheep.  相似文献   

17.
Cattle are a major reservoir of Escherichia coli 0157:H7, an important zoonotic pathogen that causes hemorrhagic colitis and hemolytic uremic syndrome (HUS). Colonization of cattle occurs predominantly in the large intestine, and may especially target follicle-associated epithelium (FAE) in the terminal rectum. Bacterial colonization involves induction of attaching-effacing (A/E) lesions, mediated by type III secreted proteins and an outer membrane protein called intimin. ToxB, encoded on plasmid pO157, contributes to adherence of E. coli O157:H7 through promotion of the production and/or secretion of type III secreted proteins. Production of type III secreted proteins and intestinal colonization appear to involve quorum-sensing mechanisms. In the human host, E. coli O157:H7 may have a preference for FAE in the distal small intestine. The H7 flagellum induces production of chemokines such as interleukin 8, and neutrophilic infiltration of the intestinal mucosa, which in turn may enhance Shiga toxin (Stx) uptake across the intestinal epithelium. Both Stx and cytokine responses play critical roles in the induction of the vascular lesions that underlie hemorrhagic colitis and HUS. In cattle, Stx binds to intestinal crypt cells and submucosal lymphocytes but not vascular endothelium. The role played by Stx in cattle may be to suppress mucosal immunity, yet enhance other effects that promote intestinal colonization.  相似文献   

18.
Escherichia coli O157:H7 and Salmonella are widely recognized as important agents of foodborne disease with worldwide distribution. The use of ionophores in feeding growing ruminants is widespread in the United States and has attracted recent interest due to the apparent temporal relationship between initial ionophore use and the increase in human E. coli O157:H7 cases. Two experiments were conducted to evaluate the effects of short-term feeding of ionophores on fecal shedding, intestinal concentrations, and antimicrobial susceptibility of E. coli O157:H7 and S. typhimurium in growing lambs. Sixteen lambs were used in each experiment, four lambs per treatment group: monensin, laidlomycin propionate, bambermycin, and a control treatment. Lambs were fed a grain and hay (50:50) diet with their respective ionophore for 12 d before experimental inoculation with E. coli O157:H7 or S. typhimurium. Animals were maintained on their respective diets an additional 12 d, and fecal shedding of inoculated pathogens was monitored daily. Lambs were killed and tissues and contents were sampled from the rumen, cecum, and rectum. No differences (P > 0.05) in fecal shedding of Salmonella or E. coli O157:H7 were observed due to treatment. Occurrence of Salmonella or E. coli in luminal contents and tissue samples from the rumen, cecum, and rectum did not differ (P > 0.05) among treatments. Feeding monensin decreased (P < 0.05) the incidence of scours in sheep infected with Salmonella compared with the other treatments. No differences in antimicrobial susceptibility were found in any of Salmonella or E. coli O157:H7 isolates. Results from these studies indicate that short-term ionophore feeding had very limited effects on E. coli and Salmonella shedding or on antimicrobial susceptibility in experimentally infected lambs.  相似文献   

19.
The objectives were to determine the effects of short-term feeding of a toxic endophyte (Neotyphodium coenophialum)-infected tall fescue seed (Festuca arundinacea, cultivar 'Kentucky 31') on fecal shedding and intestinal concentrations of Escherichia coli O157:H7 and the concentrations of prolactin, cortisol, and NEFA in experimentally inoculated ewes. Twelve ewes (mean BW = 46 +/- 2 kg) were fed a diet containing either high endophyte-infected (HI-E) or low endophyte-infected (LO-E) tall fescue seed for 7 d. Each diet consisted of 50% (as-fed basis) tall fescue seed. Ewes were experimentally inoculated with antibiotic resistance-selected E. coli O157:H7 on d 1 of the feeding treatment, and fecal shedding of inoculated pathogens was monitored daily on d 2 to 6. On d 7, ewes were weighed and euthanized, and tissues and contents were sampled from the ileum, cecum, and rectum for quantitative enumeration of E. coli O157:H7. Urine was collected at euthanization to determine total ergot alkaloid concentrations. Ewes fed HI-E had lower (P < 0.001) DMI than did ewes fed LO-E (0.8 and 1.6 +/- 0.1 kg/d of DMI for HI-E and LO-E ewes, respectively); consequently, there was a tendency (P = 0.06) for HI-E ewes to lose 0.3 +/- 0.4 kg of BW/d and LO-E ewes to gain 0.2 +/- 0.4 kg of BW/d during the 7 d. Urinary ergot alkaloids were increased (P < 0.001) in ewes fed HI-E (47.8 +/- 9.4 ng/mg of creatinine) compared with those fed LO-E (6.2 +/- 9.4 ng/mg of creatinine). Prolactin tended (P = 0.06) to be decreased in ewes fed HI-E (7.2 +/- 7.0 ng/mL) compared with those fed LO-E (27.7 +/- 7.0 ng/mL). Fecal shedding of E. coli O157:H7 tended (P = 0.06) to be increased in HI-E ewes [5.4 cfu (log10)/g of feces] compared with LO-E ewes [4.5 cfu (log10)/g of feces]. The population of E. coli O157:H7 in luminal contents from the ileum, cecum, and rectum did not differ (P > 0.36) between treatments. Treatment did not influence (P = 0.30) the occurrence of E. coli O157:H7 in cecal or rectal tissues; however, ileal tissues from HI-E ewes tended (P = 0.12) to have an increased incidence of E. coli O157:H7. Concentrations of NEFA tended (P = 0.12) to be greater in HI-E ewes than in LO-E ewes, whereas cortisol was similar (P = 0.49) for HI-E and LO-E ewes. We conclude that short-term feeding of HI-E tall fescue seed may alter the concentrations of prolactin and NEFA, and may increase fecal shedding of E. coli O157:H7 in experimentally inoculated ewes.  相似文献   

20.
Escherichia coli O157:H7 is an important food-borne pathogen and cause of hemorrhagic colitis and hemolytic uremic syndrome in humans. Cattle are an important reservoir of E. coli O157:H7, in which the organism colonizes the intestinal tract and is shed in the feces. Vaccination of cattle has significant potential as a pre-harvest intervention strategy for E. coli O157:H7; however, basic information about the bovine immune responses to important bacterial colonization factors resulting from infection has not been reported. The serum and fecal IgG and IgA antibody responses of adult cattle to E. coli O157:H7 intimin, translocated intimin receptor (Tir), E. coli-secreted proteins (Esp)A, EspB and O157 lipopolysaccharide (LPS) in response to infection were determined. All animals were seropositive for all five antigens prior to inoculation, with antibody titers to EspB and O157 LPS significantly higher (P<0.05) than those to Tir, intimin and EspA. After inoculation, the cattle became colonized and developed significant increases in their serum antibody titers to intimin, Tir, EspB, EspA and O157 LPS (P<0.05); however, by 42 days post-inoculation the titers to all except EspB were on the decline. In contrast, pre- and post-inoculation fecal IgG and IgA antibodies to these same antigens were not detected (<1:5). These results indicate that cattle respond serologically to E. coli O157:H7 type III secreted proteins, intimin and O157 LPS during the course of infection and the response is correlated with the extent of fecal shedding.  相似文献   

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