首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 984 毫秒
1.
Manipulation of cattle diets has been proposed as a possible preharvest control measure for Escherichia coli O157. Altering hindgut fermentation through diet changes may be a means to reduce fecal shedding of E. coli O157. In Exp. 1, the objective was to determine whether fecal shedding of E. coli O157 was related to fecal starch concentration. Beginning on d 20, and every week thereafter until d 61, steers in 54 pens (6 to 7 steers per pen) were sampled (n = 122) by fecal collection and rectoanal mucosal swabs (RAMS) for E. coli O157 and fecal starch concentration determinations. Escherichia coli O157 prevalence was 3.3% in fecal samples, 4.1% as measured by RAMS, and 4.9% by fecal or RAMS samples. Steers positive for E. coli O157 contained 21% more (P < 0.05) fecal starch than steers that were negative for E. coli O157. In Exp. 2, we attempted to alter the concentration of starch escaping rumen fermentation by feeding finishing diets based on steam-flaked corn (SFC) and dry-rolled corn (DRC) to 30 heifers prescreened for being culture positive for fecal E. coli O157. Beginning on d 13, heifers were sampled (feces and RAMS) weekly to monitor fecal pH and starch concentration, and prevalence of E. coli O157. Prevalence of E. coli O157 remained above 30% for the first 13 d, but declined (P < 0.05) over the entire 7-wk period. Based on RAMS, the prevalence of E. coli O157 tended to be greater (P = 0.08) for heifers fed SFC than for those fed the DRC diet. After d 20, heifers fed DRC had greater (P < 0.05) fecal starch and lower (P < 0.05) fecal pH than heifers fed SFC. Fecal pH was negatively correlated (r = - 0.34; P < 0.05; n = 143) with fecal starch concentration. Fecal starch concentration and pH were not different (P > 0.05) for heifers that were positive or negative for E. coli O157. Our data suggest that fecal shedding of E. coli O157 was not related to fecal pH or starch concentration in cattle fed grain-based diets.  相似文献   

2.
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   

3.
Crossbred beef steers (n = 615) were used in a 152-d experiment to compare steam-flaked corn (SFC) diets containing 0, 30, or 60% wet corn gluten feed (WCGF). On d 114 to 118, ruminal and fecal samples were collected from 180 steers and analyzed for pH, VFA, and total and acid-resistant Escherichia coli and coliforms. Acid resistance of E. coli and coliform populations was determined by exposure of the samples for 1 h in pH 2, 4, and 7 citric acid/sodium phosphate buffers. Increasing levels of WCGF linearly decreased total ruminal VFA (P = 0.01) and total fecal VFA (P = 0.06), but linearly increased ruminal and fecal acetate:propionate (P < 0.01) ratio and ruminal and fecal pH (P < 0.05). Feeding increasing WCGF levels resulted in a quadratic response (P < 0.05) with respect to numbers of ruminal E. coli and total coliform populations resistant to pH 4 exposure. Steers fed 30% WCGF had higher (0.7 log units) ruminal E. coli and total coliforms after exposure at pH 4 compared to steers fed 0 or 60% WCGF. Populations of E. coli and total coliforms at pH 2 and 7 were similar for all dietary treatments. Dietary WCGF linearly increased DMI (P = 0.07) and liver abscesses (P = 0.03) and linearly decreased dietary NEg (P = 0.02). Average daily gain and feed efficiencies were greatest when steers were offered 30% WCGF (quadratic, P < 0.05). Dietary manipulations that reduce acid concentrations may not correspond to changes in acid resistance of E. coli and total coliform populations detected in the gastrointestinal tracts of cattle. Moderate levels of WCGF complement SFC finishing diets.  相似文献   

4.
There has been strong debate as to whether feeding cattle hay prior to slaughter will reduce the number and/or virulence of Escherichia coli O157:H7 in the bovine gastrointestinal tract (GIT). This study addressed this issue by comparing numbers, persistence, and acid resistance of generic coliforms and E. coli O157:H7 from various gastrointestinal tract sites of cattle fed grain or hay. Mature Angus steers, doubly cannulated into the rumen and duodenum were inoculated with E. coli O157:H7. Aliquots of digesta from the rumen, duodenum, and rectum were cultured directly or acid shocked (pH 2.0) and then cultured to determine acid resistance. The culture technique used was as sensitive as standard immunomagnetic bead separation protocols. E. coli O157:H7 from hay-fed or grain-fed cattle were similarly acid resistant in all GIT locations. In contrast, generic coliforms from the rumen and rectum of hay-fed animals were more sensitive to an acid shock than coliforms from those GIT locations in grain-fed animals. E. coli O157:H7 colonized the most distal region of the GIT and was not consistently cultured from the rumen or the duodenum. Numbers in the upper GIT did not predict numbers or persistence of E. coli O157:H7 in rectal samples. Grain-feeding or hay-feeding did not affect survival of E. coli O157:H7 in the rumen, nor its passage through the abomasum (pH 2.0) to the duodenum. These data show that generic coliforms behave differently in the bovine host than E. coli O157:H7 and that E. coli O157:H7 acid resistance was independent of animal diet.  相似文献   

5.
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   

6.
The aims of the study were to determine the prevalence of enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) and other Shiga toxin-producing E. coli (STEC) in feces of white veal calves in an operation in Ontario, to evaluate exposure of the calves to EHEC O157, and to investigate the milk replacer diet and antimicrobial resistance as factors that might influence the prevalence of EHEC O157. Feces from three cohorts of 20-21 calves were collected weekly for 20 weeks and processed for isolation of EHEC O157:H7 and detection of STEC by an ELISA. Exposure to EHEC O157 was also investigated by measuring IgG and IgM antibodies to the O157 lipopolysaccharide (O157 Ab) in sera by ELISA. The prevalences of EHEC O157 were 0.17% of 1151 fecal samples and 3.2% of 62 calves, and for STEC were 68% of 1005 fecal samples and 100% of 62 calves. Seroconversion to active IgG and IgM O157 Ab responses in some calves was not associated with isolation of EHEC O157. The milk replacer contained low levels of antibodies to EHEC antigens and without antimicrobial drugs, it did not inhibit the growth of EHEC O157 in vitro. Two E. coli O157:H7 that were isolated were totally drug sensitive whereas 60 commensal E. coli isolates that were examined were highly resistant. Antibodies in milk replacer that might be protective in vivo, and susceptibility to antimicrobial agents in the milk replacer may contribute to the low prevalence of EHEC O157 in white veal calves.  相似文献   

7.
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   

8.
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   

9.
A feedlot trial was conducted to assess the efficacy of an Escherichia coli O157:H7 vaccine in reducing fecal shedding of E. coli O157:H7 in 218 pens of feedlot cattle in 9 feedlots in Alberta and Saskatchewan. Pens of cattle were vaccinated once at arrival processing and again at reimplanting with either the E. coli O157:H7 vaccine or a placebo. The E. coli O157:H7 vaccine included 50 microg of type III secreted proteins. Fecal samples were collected from 30 fresh manure patties within each feedlot pen at arrival processing, revaccination at reimplanting, and within 2 wk of slaughter. The mean pen prevalence of E. coli O157:H7 in feces was 5.0%; ranging in pens from 0% to 90%, and varying significantly (P < 0.001) among feedlots. There was no significant association (P > 0.20) between vaccination and pen prevalence of fecal E. coli O157:H7 following initial vaccination, at reimplanting, or prior to slaughter.  相似文献   

10.
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   

11.
Cattle have been recognized as a principal reservoir of Escherichia coli O157:H7. This organism appears to be confined to the gastrointestinal tract and is shed in feces. A probiotic product containing lactic acid-producing Streptococcus bovis LCB6 and Lactobacillus gallinarum LCB 12 isolated from adult cattle was developed, and a preliminary experiment was conducted to evaluate its effect on the elimination of E. coli O157 from experimentally infected calves. Eight 4-month-old Holstein calves were orally challenged with E. coli O157 and the probiotic product was administered against four calves continued fecal shedding of E. coli O157 by the 7th day after infection. Fecal shedding of E. coli O157 was completely inhibited and re-shedding was not detected in any of the animals. Remarkable increase of VFAs, especially that of acetic acid in feces after the administration of probiotic bacteria correlated with the diminution of E. coli O157. Four calves that had spontaneously ceased fecal shedding of E. coli O157 by the 7th day exhibited a high concentration of VFAs in feces before and after experimental infection. Although our results are preliminary and obtained from calves under limited conditions, the possible application of probiotic product to reduce fecal shedding of E. coli O157 from cattle is suggested.  相似文献   

12.
本试验旨在研究高谷物日粮对山羊瘤胃上皮形态结构及单羧酸转运蛋白(monocarboxylate transporter, MCT)和钠钾ATP酶mRNA表达的影响。将10头装有永久性瘤胃瘘管的健康阉割公山羊随机分为饲喂全粗料日粮的对照组(Hay,0%谷物,n=5)和饲喂高谷物日粮的处理组(HG,65%谷物,n=5),试验期为7周。试验开始后,于每周晨饲后的0、2、3、4、6、8和12 h连续采集瘤胃液监测瘤胃pH值的变化,收集其中第0、3、6和12 h的瘤胃液待测挥发性脂肪酸(volatile fatty acid, VFA)浓度。试验的第50天,屠宰采集瘤胃上皮用于形态学及基因定量分析。研究结果显示:与全粗料组山羊相比,高谷物组山羊瘤胃pH值、乙酸浓度及乙丙比都显著下降(P<0.001),而瘤胃丙酸浓度、丁酸浓度及其他VFA浓度都显著升高(P<0.001);高谷物日粮组的瘤胃乳头长度显著高于对照组(P=0.001),瘤胃乳头宽度显著低于对照组(P<0.001),但是两组间的瘤胃乳头表面积并无显著差异;透射电镜结果显示,长期饲喂高谷物日粮导致瘤胃上皮细胞线粒体发生降解;实时定量PCR结果表明,与对照组相比,高谷物日粮显著升高了MCT1(P<0.001)和钠钾ATP酶(P=0.001)的mRNA表达量,显著降低了MCT4的mRNA表达量(P=0.041),但对MCT2的表达没有显著影响(P=0.305);进一步分析这些基因的mRNA表达量与pH值和VFA浓度之间的相关性,结果显示,MCT1和钠钾ATP酶的mRNA表达量与瘤胃pH值和乙酸浓度呈显著负相关,与总VFA、丙酸、丁酸的含量呈显著正相关,而MCT4的mRNA表达量与pH值呈显著正相关,与总VFA、丙酸、丁酸的含量呈显著负相关。以上结果提示:高精料引起的瘤胃pH值下降和VFA的变化可能与瘤胃上皮MCT和钠钾ATP酶表达量的变化相关。研究结果对深入认识高谷物饲喂引发的瘤胃功能紊乱具有重要意义。  相似文献   

13.
To assess the effect of pooling fecal samples on the sensitivity of detection of E. coli O157:H7, 12 calves, inoculated orally with 10(8)cfu per calf of nalidixic acid resistant E. coli O157:H7, were used to provide positive fecal samples. After inoculation, calves were sampled twice weekly. Negative fecal samples were from calves at a local dairy. Samples from inoculated calves were incubated without pooling or were mixed with known negative fecal samples in a 1:4 ratio or a 2:3 ratio (positive:negative) for detection of E. coli O157:H7. Samples were enriched 6h in Gram negative broth with vancomycin, cefixime, and cefsoludin, underwent immunomagnetic separation with Dynabeads, and were plated onto sorbitol MacConkey agar with cefixime, and tellurite (SMACct). Morphologically typical colonies were plated onto blood agar, incubated overnight at 37 degrees C and an indole test was performed on each colony. Indole positives colonies were plated on SMAC agar with 20 microg/ml nalidixic acid (SMACnal). Colonies that grew on SMACnal were confirmed by O157 agglutination. Sensitivity of detection in non-pooled samples was 77%. Samples pooled 1:4 and 2:3 with negative samples were 55 and 52% sensitive, respectively. Pooling decreased sensitivity of detection for E. coli O157:H7 in bovine fecal samples (P<0.01). A deterministic binomial probability model was developed to assess the probability of detecting pens of cattle shedding E. coli O157 using a pooling protocol or individual samples. Pooling decreased sensitivity of detection at low pen prevalence compared to individual samples but was similar at high prevalence.  相似文献   

14.
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   

15.
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   

16.
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   

17.
Fecal samples collected from cattle at processing during a 1-year period were tested for verotoxins (VT1, VT2), Escherichia coli O157:H7, and Salmonella. Verotoxins were detected in 42.6% (95% CI, 39.8% to 45.4%), E. coli O157:H7 in 7.5% (95% CI, 6.1% to 9.1%), and Salmonella in 0.08% (95% CI, 0.004% to 0.5%) of the fecal samples. In yearling cattle, the median within-lot prevalence (percentage of positive samples within a lot) was 40% (range, 0% to 100%) for verotoxins and 0% for E. coli O157:H7 (range, 0% to 100%) and Salmonella (range, 0% to 17%). One or more fecal samples were positive for verotoxins in 80.4% (95% CI, 72.8% to 86.4%) of the lots of yearling cattle, whereas E. coli O157:H7 were detected in 33.6% (95% CI, 26.0% to 42.0%) of the lots. In cull cows, the median within-lot prevalence was 50% (range, 0% to 100%) for verotoxins and 0% (range, 0% to 100%) for E. coli O157:H7 and Salmonella (range, 0% to 0%). Verotoxins were detected in one or more fecal samples from 78.0% (95% CI, 70.4% to 84.2%) of the lots of cull cows, whereas E. coli O157:H7 were detected in only 6.0% (95% CI, 3.0% to 11.4%) of the lots of cull cows. The prevalence of verotoxins in fecal samples was lower in yearling cattle than in cull cows, whereas the prevalence of E. coli O157:H7 in fecal samples was higher in yearling cattle than in cull cows. The prevalence of E. coli O157:H7 in fecal samples was highest in the summer months. Rumen fill, body condition score, sex, type of cattle (dairy, beef), and distance travelled to the plant were not associated with the fecal prevalence of verotoxins or E. coli O157:H7. The prevalence of verotoxins in fecal samples of cull cows was associated with the source of the cattle. It was highest in cows from the auction market (52%) and farm/ranch (47%) and lowest in cows from the feedlot (31%). In rumen samples, the prevalence of verotoxins was 6.4% (95% CI, 4.2% to 9.4%), and it was 0.8% (95% CI, 0.2% to 2.3%) for E. coli O157:H7, and 0.3% (95% CI, 0.007% to 1.5%) for Salmonella.  相似文献   

18.
Six ruminally cannulated Angus-cross steers (362 kg) were used in a replicated 3 x 3 Latin square design to determine effects of supplementing Maillard reaction products (MRP) on acid-resistant E. coli and coliform populations. Steers were fed roughage-based diets supplemented (DM basis) with either 10% soybean meal (SBM), 10% nonenzymatically browned SBM (NESBM), or 10% SBM top-dressed with 45 g of a lysine-dextrose Maillard reaction product (LD-MRP). Equal weights of dextrose, lysine hydrochloride, and deionized water were refluxed to produce the LD-MRP. The NESBM was manufactured by treating SBM with invertase enzyme, followed by heating to induce nonenzymatic browning. Steers were allowed slightly less than ad libitum access to diets fed twice daily and were adapted to their respective treatments within 10 d. On d 11, ruminal and fecal samples were collected at 0, 2, 4, 6, 8, and 12 h after feeding from each of the steers and transported to the laboratory for microbial analysis. Ruminal samples and feces were analyzed for pH and VFA, and both ruminal fluid and feces were tested for acid-resistant E. coli and total coliforms by incubating samples in tryptic soy broth adjusted to pH 2, 4, and 7. Ruminal pH and total VFA concentrations did not differ among treatments. The molar proportion of ruminal acetate was higher (P < 0.05) for steers receiving NESBM than for steers receiving SBM and LD-MRP. At pH 4, steers that received NESBM had lower (P < 0.05) ruminal populations of E. coli and total coliforms than steers that received SBM. No differences were observed for ruminal E. coli and total coliforms at pH 2 and 7. Fecal pH was lower (P < 0.05) for steers fed NESBM than for steers fed SBM or LD-MRP. Molar proportions of fecal acetate were lower (P < 0.05) and proportions of butyrate and isovalerate were higher (P < 0.05) for steers fed NESBM compared with steers fed SBM. Fecal E. coli at pH 4 was lower (P < 0.05) for steers fed NESBM than for steers fed LD-MRP. Fecal E. coli and total coliforms at pH 2 and 7 did not differ among treatments. Dietary MRP had limited effectiveness at decreasing acid-resistant coliforms in the rumen and feces of cattle. Acid resistance in coliforms may depend on protein availability.  相似文献   

19.
Feed has been reported as a vehicle for transmission of Salmonella enterica in cattle and several lines of evidence suggest that feed can be a vehicle for transmitting Escherichia coli O157:H7 as well. To show whether microbial contamination of feeds could contribute to the populations of S. enterica and E. coli O157:H7 on a farm, we compared isolates from feed samples to bovine fecal isolates from the same farm using pulsed-field gel electrophoresis (PFGE). Four of 2365 component feed samples (0.2%) and 1 of 226 feed mill samples (0.4%) were positive for E. coli O157:H7. Twenty of 2405 (0.8%) component feed samples and none of 226 feed mill samples were positive for Salmonella. PFGE profiles from E. coli O157:H7 isolated from a component feed sample closely resembled that from a fecal isolate collected later from the same farm, and a similar observation was made of a Salmonella Tyhpimurium isolate from component feed on another farm. There were indistinguishable PFGE profiles from component feed Salmonella Tyhpimurium DT104 isolates and fecal isolates from the same farm. These results provide evidence for a role of cattle feed in transmission of E. coli O157:H7; S. enterica; cattle-bacteria.  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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号