Campylobacter spp. in Irish Feedlot Cattle: A Longitudinal Study Involving Pre‐harvest and Harvest Phases of the Food Chain

The aim of this study was to investigate faecal shedding and transmission of Campylobacter spp. in cohorts of cattle within a feedlot, to assess subsequent contamination of carcasses with this pathogen and to identify risk factors associated with faecal shedding of Campylobacter spp. A cohort of 133 heifers housed in four adjacent pens was examined over a five and a half month period, from entering the feedlot to slaughter. A parallel investigation of individual rectal faecal samples and pen environmental samples were taken at monthly intervals from November to February. The entire outer and inner surfaces of a carcass side of each animal were swabbed immediately following slaughter. Campylobacter spp. were isolated from 322 (54%) of the 600 rectal faecal samples. Campylobacter jejuni and C. coli accounted for 69 and 29.7% of the isolate recovered, respectively. A total of 159 environmental samples were examined, of these Campylobacter spp. was isolated from 46 samples (29%). Campylobacter jejuni and C. coli accounted for 35 and 59% of these isolates, respectively. Campylobacter spp. was not isolated from any of the dressed carcasses. Logistic regression indicated prevalence of Campylobacter spp. faecal shedding within pens was positively correlated to the pen, the month of sampling and the Campylobacter spp. contamination status of the pen dividing bars and the water trough surface. Campylobacter spp. should be considered as a pathogen shed in the faeces of a substantial proportion of feedlot cattle. However, with good hygienic practice during harvest, a very low level of this pathogen can be achieved on dressed carcasses.     

An investigation on the effect of transport and lairage on the faecal shedding prevalence of Escherichia coli O157 in cattle

The aim of the study was to investigate the effect of transport and lairage on the prevalence of Escherichia coli O157 faecal shedding and the subsequent contamination of beef carcasses. Individual rectal faecal samples were taken from two cohorts of cattle (109 and 59) at the farm before transport and at the abattoir post-transport and lairage. The entire outer and inner surfaces of the carcass of each animal were swabbed immediately following slaughter and dressing. The prevalence of E. coli O157 shedding in cattle sampled at farm, post-transport and lairage was 18% (20), 13% (14) and 12% (13) for cohort A and 1.7% (1), 1.7% (1) and 0 for cohort B, respectively. No E. coli O157 was recovered from the 168 dressed carcasses. In total, 98% (46 of 47) of the E. coli O157 isolates from cohort A were potentially pathogenic to man. Transport and lairage do not cause an increase in the prevalence of E. coli O157 faecal shedding in cattle. This study demonstrates that even positive cohorts of cattle may be slaughtered and processed to produce clean carcasses by following good hygienic practices.     

Prevalence of Campylobacter spp. and Yersinia spp. in the pig production

The aim of this study was to determine the prevalence of Campylobacter spp. and Yersinia spp. in a total of 1,040 faecal samples taken from animals at different ages from four farrowing and twelve fattening herds. In the farrowing unit, faeces were collected from 68 sows (faecal samples) and 256 suckling piglets (rectal swab samples). Further samples were collected from 362 growing and 354 finishing pigs (rectal swab samples). Additionally, 56 feed and environmental samples were collected. During the slaughtering process, 122 pigs and their carcasses respectively, were sampled three times. Finally, 86 meat and minced meat samples were taken from 34 retail stores. Campylobacter spp. were isolated in sows (33.8 %), piglets (80.9 %), growing (89.2 %) and finishing (64.7 %) pigs. Yersinia spp. were detected in growing (15.2 %) and finishing (13.3 %) pigs only. After twelve hours of chilling neither Campylobacter spp. nor Yersinia spp. were detected. In raw meat samples, Campylobacter spp. were isolated from one liver sample and Yersinia enterocolitica from two meat samples. Common slaughter techniques and hygiene procedures may be effective tools to reduce the risk of contamination and recontamination of meat products since Campylobacter spp. and Yersinia spp. were found only sporadically in raw meat samples.     

Distribution and genetic characterization of porcine Campylobacter coli isolates

The aim of this study was to evaluate the impact of the slaughter process on the Campylobacter (C.) coli prevalence on pig carcasses and finally pork. To detect C. spp., faecal samples, organ samples and surfaces of slaughter pigs were sampled. Additionally, various abattoir surfaces (n=208) and 227 pork and minced meat samples were included in our study.Whereas a high C. spp. prevalence (64.0%) was detectable in the faeces of slaughter pigs (all isolates were identified as C. coli), low detection rates were observed on pig carcasses after the slaughter process before the chilling period (21.1%).The impact of chilling reduced the detection rate of C spp. on pig carcasses even further to 0.8%. Only C. jejuni strains were isolated after the chilling process. Chilling and the associated drying of the skin are responsible for that massive reduction of C. spp prevalence. Significantly more C. spp. were isolated from livers compared to the corresponding carcasses. Only 5 out of 208 swab samples from different surfaces of the abattoir were C. coli positive. Bacteriological investigation could not detect any C. spp. strains from pork and minced pork meat.The low detection rates at the end of the slaughter and processing line indicate that pork may only play a minor role in the transmission of C. coli infections to humans. By genotyping C. coli-isolates from selected animals we were able to demonstrate three possible ways of contamination of the slaughter carcass surface. Genetically highly related strains were detectable on carcass surfaces of consecutively slaughtered animals. Faecal isolates and isolates from the carcass surface showed occasional high similarities. C. coli-genotypes from tonsils and genotypes from the corresponding slaughter carcasses formed a close cluster.     

Escherichia coli O157:H7 vaccine field trial in 9 feedlots in Alberta and Saskatchewan

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.     

The characterisation of E. coli O157:H7 isolates from cattle faeces and feedlot environment using PFGE

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.     

Effects of using retention-pond water for dust abatement on performance of feedlot steers and carriage of Escherichia coli O157 and Salmonella spp

OBJECTIVE: To evaluate the effects of using retention-pond water for dust abatement on performance of feedlot steers and carriage of Escherichia coli O157 and Salmonella spp. DESIGN: Matched cohort studies. ANIMALS: 2 groups of feedlot steers comprising 3,510 (pathogen carriage) and 3,737 (performance) animals housed in a large commercial feedlot in the Texas Panhandle. PROCEDURE: Steers were systematically allocated to treatment pens approximately 60 days after arrival (pathogen carriage) or at arrival (performance). For evaluation of pathogen carriage, feces and hide swab specimens were collected from 25 animals in each pen within 10 days of slaughter. Samples were submitted for bacterial culture for E. coli O157 and were tested with a polymerase chain reaction-based assay for Salmonella spp. For evaluation of performance, pen weights of animals were obtained at arrival and slaughter and feed delivered to each pen was recorded. The exposure of interest for both studies was application of retention-pond water through fixed high-pressure sprinklers. RESULTS: Carriage of E. coli O157 and Salmonella spp and animal performance were not adversely affected by exposure to retention-pond water. Prevalences of E. coli O157 in feces, on hides, and either in feces or on hides for those exposed to retention-pond water were 8.3%, 8.9%, and 15.4%, respectively; prevalences for those unexposed to retention-pond water were 11.4%, 15.4%, and 22.6%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that use of retention-pond water for dust abatement in feedlot pens does not adversely affect pathogen carriage or animal performance.     

Comparison of fecal samples collected per rectum and off the ground for estimation of environmental contamination attributable to beef cattle

OBJECTIVES: To determine whether sampling feces off the ground replicates prevalence estimates for specific pathogens obtained from fecal samples collected per rectum of adult cows, and to determine characteristics of feces on the ground (fecal pats) that are associated with subsequent identification of Campylobacter spp, Cryptosporidium parvum, and Giardia duodenalis. ANIMALS: A random sample of adult beef cattle from 25 herds located throughout California. PROCEDURE: 1,115 rectal and ground fecal samples were obtained. Samples were submitted for culture of Campylobacter spp and examined, using a direct fluorescent antibody assay, to detect C parvum oocysts and G duodenalis cysts. Characteristics of fecal pats, such as volume and consistency, were recorded. RESULTS: Prevalence of Campylobacter spp was 5.0% (20/401) for rectal fecal samples, which was significantly greater than prevalence determined for ground fecal samples (2/402; 0.5%). Most isolates were C jejuni subsp jejuni. Prevalence of C parvum was higher in rectal fecal samples (6/557; 1.1%) than in ground fecal samples (1/558; 0.2%), but this difference was not significant. Prevalence of G duodenalis did not differ for rectal (36/557; 6.5%) versus ground (26/558; 4.7%) fecal samples. CONCLUSIONS AND CLINICAL RELEVANCE: Evaluation of ground fecal samples may not accurately indicate the prevalence of Campylobacter spp or C parvum in cattle but may reflect prevalence of G duodenalis. Differences in prevalence estimates between the 2 methods suggest inactivation of pathogens in feces after cattle have defecated. Prevalence estimates generated by evaluation of ground fecal samples, however, may more accurately estimate environmental pathogen burden.     

Prevalence of Campylobacter jejuni and Salmonella during pig slaughtering

It was found that 79% of healthy pigs, slaughtered in three different slaughterhouses in the Netherlands, were intestinal carriers of Campylobacter jejuni (mean number 4000 cfu per g), and 21% of the same pigs had Salmonella in the intestinal tract (mean number 10 cfu per g). Immediately after slaughter, Campylobacter was swabbed from 9% of the carcasses and Salmonella from 13%. It is concluded from these data that most of the contamination on carcasses does not originate directly from the intestinal tracts of the animals but rather from surfaces, equipment, and utensils in the slaughter hall. It was demonstrated that Salmonella could survive in the slaughter hall, whereas Campylobacter died off, probably due to its vulnerability to drying conditions and its inability to grow at temperatures below 30 degrees C. Campylobacter was not isolated from the carcasses after cooling. It had been shown earlier that this again was caused by dry conditions, brought about by the use of forced ventilation in the cooling rooms. In an additional investigation, Campylobacter was not isolated from 248 samples of minced pork (10 g each), whereas Salmonella was found in 13% of these samples.     

Occurrences of thermophilic <Emphasis Type="Italic">Campylobacter</Emphasis> in cattle slaughtered at Morogoro municipal abattoir,Tanzania

An investigation was conducted in Morogoro municipality to assess the likelihood of slaughter cattle posing public health risk of contaminating carcasses with thermophilic Campylobacter. Butchers and meat shopkeepers were interviewed on source of slaughter cattle, method of animal and carcass transportation, carcass dressing, meat storage facilities, access to clean water and availability of food hygiene practices. Faecal samples were collected from 107 slaughter cattle and after slaughter; four different parts of dressed carcasses (i.e. from ham, neck, pelvis and thigh muscles) were also sampled. In addition 107 cattle meat samples for Campylobacter culture were collected in different meat shops. The samples were subjected to standard bacteriological examination using Skirrows protocol. It was found that cattle slaughter, dressing and meat handling in meatshops was done under unhygienic condition. Thermophilic Campylobacter prevalence in slaughter cattle was 5.6% while contamination rate of dressed carcasses and cattle meat at shops was 9.3% and 1.9%, respectively. The majority of thermophilic Campylobacter isolated were C. jejuni (88.9%) while C. coli was isolated at 11.1%. Findings of this study suggest possibility of humans acquiring zoonotic Campylobacter infections from cattle meat particularly when meat preparation and processing is not done properly. More work is required to establish the magnitude of zoonotic enteric Campylobacteriosis in humans and epidemiological role of cattle and other animals in the study area.     

Antimicrobial resistance in Campylobacter spp. isolated from Ontario sheep flocks and associations between antimicrobial use and antimicrobial resistance

The objectives of this study were to determine the prevalence of antimicrobial resistance (AMR) in faecal Campylobacter spp. from lambs and adult sheep and associations between antimicrobial use (AMU) and AMR. A total of 275 faecal samples collected during initial and final visits from 51 sheep flocks, including one feedlot, across southern Ontario were tested for the presence of Campylobacter spp. Campylobacter jejuni was detected in 52% (143/275) of the faecal samples, Campylobacter coli in 7% (19/275), Campylobacter lari in 1% (2/275) and 2% (4/275) were non-speciated Campylobacter. Broth microdilution was used to test antimicrobial susceptibility of 162 isolates to nine antimicrobials. Campylobacter jejuni isolates (n = 142) were resistant to tetracycline (39%), ciprofloxacin (4%), nalidixic acid (4%) and telithromycin (1%). C. coli isolates (n = 19) were resistant to tetracycline (74%), and azithromycin, clindamycin, erythromycin, and telithromycin (5%). The C. lari isolate displayed resistance to nalidixic acid. No statistically significant associations were found between AMU and AMR during multivariate modelling in this study.     

Presence of non-O157 Shiga toxin-producing Escherichia coli in feces from feedlot cattle in Alberta and absence on corresponding beef carcasses.

The study objectives were to determine the prevalence and serotypes of non-O157 Shiga toxin-producing Escherichia coli (STEC) in pens of feedlot cattle and on corresponding beef carcasses. We collected 25 fecal samples from 84 pens in 21 Alberta feedlots and 40 carcass swabs from each preslaughter pen for analysis by culture and polymerase chain reaction (PCR). Non-O157 STEC were recovered from feces from 12 (14%) of the 84 pens and 12 (57%) of the 21 feedlots by examination of 1 E. coli isolate positive for 4-methylumbelliferyl-beta-beta-glucuronide per sample. Twelve non-O157 serotypes were detected, but 7 of the 15 STEC isolates lacked the accessory virulence genes eae and hlyA. Although 115 (7%) of the carcass broths were PCR-positive, no STEC isolates were recovered from the 1650 carcasses sampled. Our data indicate that multiple non-O157 STEC serotypes may be present in cattle feces, yet are unlikely to be recovered from the corresponding beef carcasses when 20 colonies per sample from PCR-positive broth cultures are analyzed.     

Management and nutritional factors associated with the detection of Salmonella sp. from cattle fecal specimens from feedlot operations in the United States

In a convenience sample of 100 feedlot operations (included in the United States Department of Agriculture: Animal and Plant Health Inspection Service 1994 Cattle on Feed Evaluation), up to 25 cattle fecal samples were collected and tested for the presence of Salmonella from each of two pens (the pen which contained the most-recent arrivals, and the pen with cattle that had been on feed the longest). One or more Salmonella spp. were recovered from 38 (38.0%) of the 100 feedlots, 52 (26.0%) of the 200 pens and 273 (5.5%) of the 4977 fecal samples collected. Multivariable logistic regression indicated that feeding tallow and feeding whole cottonseed or cottonseed hulls within seven days prior to fecal sample collection was associated with an increased risk of finding Salmonella in a pen. Variables not found to be significantly associated with the detection of Salmonella in a pen included region, operation size, use of sprinklers, time on feed, type of cattle in the pen, number and concentration of cattle in a pen, feeding probiotics, and various other feeds.     

Comparison of sampling techniques for measuring the antimicrobial susceptibility of enteric Escherichia coli recovered from feedlot cattle

OBJECTIVE: To evaluate the effectiveness of various sampling techniques for determining antimicrobial resistance patterns in Escherichia coli isolated from feces of feedlot cattle. SAMPLE POPULATION: Fecal samples obtained from 328 beef steers and 6 feedlot pens in which the cattle resided. PROCEDURE: Single fecal samples were collected from the rectum of each steer and from floors of pens in which the cattle resided. Fecal material from each single sample was combined into pools containing 5 and 10 samples. Five isolates of Escherichia coli from each single sample and each pooled sample were tested for susceptibility to 17 antimicrobials. RESULTS: Patterns of antimicrobial resistance for fecal samples obtained from the rectum of cattle did not differ from fecal samples obtained from pen floors. Resistance patterns from pooled samples differed from patterns observed for single fecal samples. Little pen-to-pen variation in resistance prevalence was observed. Clustering of resistance phenotypes within samples was detected. CONCLUSIONS AND CLINICAL RELEVANCE: Studies of antimicrobial resistance in feedlot cattle can rely on fecal samples obtained from pen floors, thus avoiding the cost and effort of obtaining fecal samples from the rectum of cattle. Pooled fecal samples yielded resistance patterns that were consistent with those of single fecal samples when the prevalence of resistance to an antimicrobial was > 2%. Pooling may be a practical altemative when investigating patterns of resistance that are not rare. Apparent clustering of resistance phenotypes within samples argues for examining fewer isolates per fecal sample and more fecal samples per pen.     

Effects of wheat or corn distillers dried grains with solubles on feedlot performance, fecal shedding, and persistence of Escherichia coli O157:H7

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.     

Behavior of feedlot cattle affects voluntary oral and physical interactions with manila ropes

Providing cattle with access to manila ropes has shown promise as a means of monitoring zoonotic bacteria in pens of feedlot cattle. Studies were conducted to determine the impacts of climate, animal age and BW, number of ropes, duration of placement, and previous rope access on efficacy of ropes as a sampling technique for feedlot cattle. Eight pens of commercial finishing cattle (average 196 +/- 19 animals per pen, 536.7 +/- 22.9 kg) were monitored for a total of 7 d in October of 2003 (commercial study). One rope was tied on the pen railing adjacent to the feed bunk in each pen, and the proportion of animals within the pen contacting the rope was recorded. In a second study, 80 cattle housed in 8 pens (each 270 m(2); 10 animals/pen) were monitored for 1 d/wk using video cameras (video study). Video images were collected for 8 consecutive weeks immediately after weaning (average BW = 252.7 +/- 30.6 kg) and for 6 wk at the end of the finishing period (average BW 541.2 +/- 42.8 kg). In the commercial study, the proportion of cattle contacting the rope per pen increased over the first 6 h to 70% (P < 0.05), although approximately 50% of the cattle contacted the rope within 2 h after placement. A 40 degrees C reduction in ambient temperature on d 6 caused cattle to cease contact with the ropes, although after 6 d of acclimation to reduced ambient temperature, interactions with ropes recovered to 47% of previous values. In the video study, weaned calves required 2 wk of acclimation to the feedlot environment before contact with the rope was maximized. Contact with the rope was most frequent 3 to 8 wk after entry into the feedlot and decreased (P < 0.05) as cattle approached slaughter weight. It is likely that ropes will be most effective at monitoring zoonotic bacteria in pens of cattle during the mid-feeding period where the pen environment is stable and cattle are inquisitive but not highly reactive.     

Stochastic Simulation Model Comparing Distributions of STEC O157 Faecal Shedding Prevalence Between Cattle Vaccinated With Type III Secreted Protein Vaccines and Non‐Vaccinated Cattle

Pens of cattle with high Escherichia coli O157:H7 (STEC O157) prevalence at harvest may present a greater risk to food safety than pens of lower prevalence. Vaccination of live cattle against STEC O157 has been proposed as an approach to reduce STEC O157 prevalence in live cattle. Our objective was to create a stochastic simulation model to evaluate the effectiveness of pre‐harvest interventions. We used the model to compare STEC O157 prevalence distributions for summer‐ and winter‐fed cattle to summer‐fed cattle immunized with a type III secreted protein (TTSP) vaccine. Model inputs were an estimate of vaccine efficacy, observed frequency distributions for number of animals within a pen, and pen‐level faecal shedding prevalence for summer and winter. Uncertainty about vaccine efficacy was simulated using a log‐normal distribution (mean = 58%, SE = 0.14). Model outputs were distributions of STEC O157 faecal pen prevalence of summer‐fed cattle unvaccinated and vaccinated, and winter‐fed cattle unvaccinated. The simulation was performed 5000 times. Summer faecal prevalence ranged from 0% to 80% (average = 30%). Thirty‐six per cent of summer‐fed pens had STEC O157 prevalence >40%. Winter faecal prevalence ranged from 0% to 60% (average = 10%). Seven per cent of winter‐fed pens had STEC O157 prevalence >40%. Faecal prevalence for summer‐fed pens vaccinated with a 58% efficacious vaccine product ranged from 0% to 52% (average = 13%). Less than one per cent of vaccinated pens had STEC O157 prevalence >40%. In this simulation, vaccination mitigated the risk of STEC O157 faecal shedding to levels comparable to winter, with the major effects being reduced average shedding prevalence, reduced variability in prevalence distribution, and a reduction in the occurrence of the highest prevalence pens. Food safety decision‐makers may find this modelling approach useful for evaluating the value of pre‐harvest interventions.     

Isolation of Listeria monocytogenes from the skin of slaughtered beef cattle

We attempted to isolate Listeria monocytogenes from skin, contents of large intestines and carcasses of cattle introduced to a slaughterhouse in order to identify source of contamination for this pathogen. Sixty skin samples, 60 samples of the contents of large intestines and 30 carcass samples were colleted in June, August and November 2003 for use in this study. Listeria spp. and L. monocytogenes were isolated from 30 (50%) and 3 (5%) of the cattle skin samples, respectively. However, no Listeria spp., including L. monocytogenes, were isolated from intestinal contents or carcasses. Seven isolates were obtained, of which five and two strains were serotypes 1/2a and 1/2b, respectively. Genetic analysis suggested that there was persistent inhabitation of the pathogen around the area investigated in this study.     

Factors associated with the presence of Escherichia coli O157 in feedlot-cattle water and feed in the Midwestern USA

Our objective was to generate hypotheses about associations between management, climate, and the presence of Escherichia coli O157 in feedlot–cattle water tanks and in feedlot–cattle feed. Water samples from 710 tanks on 73 feedlots, and feed-samples from a subset of 504 pens on 54 feedlots, in four US states were tested for E. coli O157. Management and climate factors were ascertained by survey and observation. Escherichia coli O157 were isolated from 13% of the water tanks and at least one water tank was positive on 60% of the feedlots. The factors significantly associated with E. coli O157 in water were greater percentage of cattle shedding E. coli O157 in faeces within the same pen, higher concentration of total E. coli in the water, lack of the clarity of the water, the use of fly traps, the reported frequency of rodent sightings in the pen or alley area, and the weather at the time of sampling. Escherichia coli O157 were isolated from 14.9% of the feed samples obtained from the feedbunks. Factors positively associated with E. coli O157 in feed were higher heat index at the time of sampling, the presence of cottonseed meal in the ration, and the feedlot location (state). Coliform counts in feed, presence of E. coli O157 in water tanks and faecal prevalence of E. coli O157 were not associated with the presence of E. coli O157 in feed.     

Serum agglutinin titers against somatic and flagellar antigens of Campylobacter jejuni and isolation of Campylobacter spp in chickens

From June 1983 to June 1984, two hundred twenty-five 3- to 30-month-old chickens (hens) on 10 different farms were examined for Campylobacter spp. Watering trays and fly vectors also were examined for Campylobacter spp on 6 of the 10 farms. Campylobacter jejuni was isolated from fecal specimens from 64 hens (28.4%), C coli was isolated from 6 hens (2.7%), and C laridis was isolated from 9 hens (4%). The isolation rate of C jejuni was 6.7% to 46.7% for 9 of the 10 farms. On 2 farms, agglutinin titers greater than or equal to 1:40 against somatic and flagellar antigen of C jejuni were detected in hens from which the bacteria were isolated. Hens having titers greater than or equal to 1:40 against C jejuni or hens from which C jejuni had been isolated often occupied adjacent pens. Campylobacter jejuni was isolated from a watering tray on 1 farm and from fly vectors on 2 farms.