Spread of marker bacteria from the hides of cattle in a simulated livestock market and at an abattoir

Beef abattoir interventions in a risk-based meat safety assurance system

In risk-based meat safety assurance system, the use of interventions is intended to accomplish the meat safety targets on chilled carcasses, particularly in situations when an abattoir is unable to sufficiently reduce risks arising from specific farms/animal batches by using process hygiene alone. Furthermore, interventions are considered whenever food safety authorities identify meat production processes associated with high risks for consumers. This paper overviews the role of beef interventions in a risk-based, meat safety assurance system. Cattle hide interventions (chemical hide washes and microbial immobilisation treatment with shellac) and beef carcass interventions (pasteurisation treatments with hot water and/or steam and organic (lactic) acid washes), show consistent reduction effects of aerobic bacteria and faecal indicators and reduced prevalences of naturally present VTEC and Salmonella. The review also identified interventions where there was a lack of data and further research was needed, and other contextual factors to inform the risk management decisions for further development of risk-based meat safety assurance system.

A Comparison of 16S rRNA Profiles Through Slaughter in Australian Export Beef Abattoirs

Microbial contamination of beef cattle carcases and subsequent cross-contamination during processing is inevitable and virtually impossible to prevent. The understanding of microbial contamination in the beef industry is currently limited to hypotheses based on traditional microbiological tools. Additionally, the complex structural and functional responses of beef cattle microbial communities to the fragmentation in the supply chain remain unknown. This study used 16S rRNA gene sequencing in combination with traditional microbiology to monitor and compare changes in the microbiota throughout slaughter in an integrated (abattoir A) and a fragmented (abattoir B) beef abattoir in Australia. Briefly, the primary difference between an integrated and a fragmented abattoir is that fragmented abattoirs receive cattle from multiple sources, whereas integrated abattoirs typically receive cattle that has been produced using the same production system and from a limited number of sources. The composition in the bacterial communities varied between the abattoirs, though the presence of the most predominant bacterial species within the microbiota at each abattoir was similar. Lactobacillales (2.4-56.2%) and Pseudomonadales (2.4-59.4%) most notably dominated hides, carcases, and the environment in abattoir B. In abattoir A, Bacteroidales (3.9-43.8%), Lactobacillales (0.0-61.9%), and Pseudomonadales (0.5-72.1%) fluctuated but generally shared the dominance over the rest. Combined results of total viable count (TVC) and 16S rRNA gene profiling indicated that an upward hide pulling system adopted by abattoir B may lead to increased transmission of hide contaminants to post-hide pull carcases. Abattoir B had 3.2 log₁₀CFU/cm² reduction from hide to carcase, where abattoir A had 4.5 log₁₀CFU/cm² reduction. The findings from this study indicated that common beef-associated microbiota exist in varying composition in Australian abattoirs, and 16S rRNA amplicon sequencing is a powerful tool to understand in-depth movement of microbial contaminants.

Presence of pathogenic Escherichia coli is correlated with bacterial community diversity and composition on pre-harvest cattle hides

BACKGROUND

Since 1982, specific serotypes of Shiga toxin-producing Escherichia coli (STEC) have been recognized as significant foodborne pathogens acquired from contaminated beef and, more recently, other food products. Cattle are the major reservoir hosts of these organisms, and while there have been advancements in food safety practices and industry standards, STEC still remains prevalent within beef cattle operations with cattle hides implicated as major sources of carcass contamination. To investigate whether the composition of hide-specific microbial communities are associated with STEC prevalence, 16S ribosomal RNA (rRNA) bacterial community profiles were obtained from hide and fecal samples collected from a large commercial feedlot over a 3-month period. These community data were examined amidst an extensive collection of prevalence data on a subgroup of STEC that cause illness in humans, referred to as enterohemorrhagic E. coli (EHEC). Fecal 16S rRNA gene OTUs (operational taxonomic units) were subtracted from the OTUs found within each hide 16S rRNA amplicon library to identify hide-specific bacterial populations.

RESULTS

Comparative analysis of alpha diversity revealed a significant correlation between low bacterial diversity and samples positive for the presence of E. coli O157:H7 and/or the non-O157 groups: O26, O111, O103, O121, O45, and O145. This trend occurred regardless of diversity metric or fecal OTU presence. The number of EHEC serogroups present in the samples had a compounding effect on the inverse relationship between pathogen presence and bacterial diversity. Beta diversity data showed differences in bacterial community composition between samples containing O157 and non-O157 populations, with certain OTUs demonstrating significant changes in relative abundance.

CONCLUSIONS

The cumulative prevalence of the targeted EHEC serogroups was correlated with low bacterial community diversity on pre-harvest cattle hides. Understanding the relationship between indigenous hide bacterial communities and populations may provide strategies to limit EHEC in cattle and provide biomarkers for EHEC risk assessment.

Peri- and Postharvest Factors in the Control of Shiga Toxin-Producing Escherichia coli in Beef

Certain Shiga toxin-producing Escherichia coli (STEC) strains are important causes of food-borne disease, with hemorrhagic colitis and, in some cases, hemolytic-uremic syndrome as the clinical manifestations of illness. Six serogroups and one serotype of STEC (O26, O45, O103, O111, O121, O145, and O157:H7) are responsible for the vast majority of cases in the United States. Based on recent data for all food commodities combined, 55.3% and 50.0% of the outbreaks of STEC O157 and non-O157 in the United States, respectively, are attributable to beef as a food source. Consequently, the U.S. Department of Agriculture, Food Safety and Inspection Service declared these organisms as adulterants in raw, nonintact beef. In North America, cattle are a major reservoir of STEC strains, with organisms shed in the feces and contaminated hides of the animals being the main vehicle for spread to carcasses at slaughter. A number of peri- and postharvest interventions targeting STEC have been developed, and significant progress has been made in improving the microbiological quality of beef in the past 20 years as a result. However, continued improvements are needed, and accurate assessment of these interventions, especially for non-O157 STEC, would greatly benefit from improvements in detection methods for these organisms.

Distribution and decline of human pathogenic bacteria in soil after application in irrigation water and the potential for soil-splash-mediated dispersal onto fresh produce

AIMS

To improve our understanding of the survival and splash-mediated transfer of zoonotic agents and faecal indicator bacteria introduced into soils used for crop cultivation via contaminated irrigation waters.

METHODS AND RESULTS

Zoonotic agents and an Escherichia coli marker bacterium were inoculated into borehole water, which was applied to two different soil types in early-, mid- and late summer. Decline of the zoonotic agents was influenced by soil type. Marker bacteria applied to columns of two soil types in irrigation water did not concentrate at the surface of the soils. Decline of zoonotic agents at the surface was influenced by soil type and environmental conditions. Typically, declines were rapid and bacteria were not detectable after 5 weeks. Selective agar strips were used to determine that the impact of water drops 24-87 μl could splash marker bacteria from soil surfaces horizontal distances of at least 25 cm and heights of 20 cm.

CONCLUSIONS

Soil splash created by rain-sized water droplets can transfer enteric bacteria from soil to ready-to-eat crops. Persistence of zoonotic agents was reduced at the hottest part of the growing season when irrigation is most likely.

SIGNIFICANCE AND IMPACT OF THE STUDY

Soil splash can cause crop contamination. We report the penetration depths and seasonally influenced declines of bacteria applied in irrigation water into two soil types.

Effects of long- or short-haul transportation of slaughter heifers and cattle liner microclimate on hide contamination with Escherichia coli O157

Effects of cattle transportation on hide contamination with Escherichia coli O157 have been variable, and the present study was designed to clarify relationships among duration of transport, microclimate, and environment within the trailer and contamination of hides with E. coli O157. Crossbred Angus heifers from a feedlot in southern Alberta were sorted into 10 replicate loads containing 45 animals (short haul, 621.5 ± 2.1 kg of body weight) or 46 animals (long haul, 576.0 ± 1.7 kg of body weight). Long-haul trips (n = 5) were made in July and August to slaughter plant A, whereas short-haul trips (n = 5) were made in October to slaughter plant B. The same trailer unit and driver were used for all loads. Data loggers were located in the ceiling of each compartment of the trailers to record ambient temperature and relative humidity. Each heifer was swabbed on the perineum on-farm prior to loading and immediately after stunning at the slaughter plant (an average 12-h transport for long haul and 1-h transport for short haul). Swabs were transported on ice before immunomagnetic separation for detection of E. coli O157. Transportation did not affect prevalence of hide contamination with E. coli O157, although 80% of long-haul swabs were positive on-farm compared with 26% of short-haul swabs, due to seasonality of shedding E. coli O157. Cattle transported in the nose compartment had fewer positive hide swabs (P < 0.05) than cattle in the deck or belly compartments during long-haul trips, even though the nose had a higher (P < 0.05) temperature-humidity index than the other compartments. Prevalence of hide contamination varied widely among loads even when the organism was at seasonally low levels. This suggests that the feedlot pen has a greater effect on hide contamination at the slaughter plant than transportation factors including temperature-humidity index, loading density, and duration of transport.

Use of model super-shedders to define the role of pen floor and hide contamination in the transmission of Escherichia coli O157:H7

Super-shedders, cattle shedding at least 10(4) cfu of Escherichia coli O157:H7 per gram of feces, increase the risks of contaminating the food chain and disseminating the organism through cattle populations. Because detecting super-shedders in cattle populations is laborious and time-consuming, a study was conducted to evaluate the role of hide and pen-floor contamination by model super shedders (MSS) in transmission of E. coli O157:H7. Steers (n = 48) negative for E. coli O157:H7 were allocated to 6 pens, with 2 replicate pens per treatment. Treatment A consisted of 3,000 g of feces inoculated with 10(6) cfu/g of a 5-strain mixture of nalidixic acid-resistant E. coli O157:H7 and spread in simulated fecal pats on the pen floor for d 0 through 4 and d 14 through 18. For treatment B, 100 g of the feces per day was spread on the perineum of 1 MSS per pen, and the remaining feces was placed on the pen floor as fecal pats similar to treatment A. Treatment C differed from B in that 50 g of feces was spread on the perineum and 50 g on the brisket of the MSS steer. Fecal samples, perineal swabs (500-cm(2) area around the anus), freshly voided fecal pats and manila rope samples were collected during a 56-d experimental period. More positive rope samples were found in treatments B and C compared with A (P = 0.05), and steers within treatments B and C were 1.3 times more likely (P = 0.05) to shed E. coli O157:H7 in their feces than steers in treatment A. Even though the number of E. coli O157:H7 introduced into pens was similar, results indicate an increased importance of hide compared with pen-floor contamination for transmission of this organism to cattle. Because cattle within treatment B were persistently colonized with E. coli O157:H7, this design should prove suitable for future studies investigating the role of super-shedders in the transmission of E. coli O157:H7.

The occurrence of Escherichia coli O157 in/on faeces, carcasses and fresh meats from cattle

The aim of this study was to investigate whether Escherichia coli O157 is present in/on raw beef in Serbia. Correlated faecal and carcasses samples from 115 slaughtered cattle plus 26 uncorrelated carcass samples were examined. E. coli O157 detection and identification was performed using selective enrichment and immunomagnetic separation followed by selective media-plating and biochemical tests. The E. coli O157 occurrences were 2.6% in faeces and 2.8% on carcasses. The E. coli O157 occurrences were 0%, 6.2% and 2.1%, respectively, in 106 samples of beef trimmings, 48 samples of minced beef and 48 samples of batter intended for production of raw, fermented sausages. The results confirmed that faecal contamination is very important for the occurrence of E. coli O157 on beef carcasses. Furthermore, the present study revealed occasional presence of the pathogen in raw materials used for producing raw, fermented beef sausages.

Factors associated with cross-contamination of hides of Scottish cattle by Escherichia coli O157

The putative source of hide contamination for 236 cattle in Scotland followed from the farm through to slaughter was determined using phage and verocytotoxin type data. The majority of cattle (84%) were found to have subtypes of Escherichia coli O157 on their hide that had not been found previously in any animal from the farm of origin, strongly suggesting that contamination occurred once animals had left the farm of origin. Using logistic regression analysis, several variables and factors were found to be strongly associated (P < 0.01) with cross-contamination of cattle hides at the univariate level; commercial transport to slaughter, transport with other animals, use of a crush, line automation, and increasing slaughterhouse throughput were all risk factors, while feeding hay in lairage, processing an animal earlier in a slaughter cohort, and cleaning the landing area poststunning were protective. In the multivariable model, with the slaughterhouse and the farm group included as random effects, factors associated with the cross-contamination of cattle hides were identified. Transport to the slaughterhouse by a commercial hauler had a borderline-significant association with increased odds of an animal having a cross-contaminated hide (odds ratio [OR] [95% confidence interval (CI)] = 5.7 [0.99, 33.0]; P = 0.05). At the slaughterhouse, providing hay to cattle waiting in lairage (OR [95% CI] = 0.04 [<0.01, 1.04]; P = 0.05) and cleaning the landing area (OR [95% CI] = 0.03 [<0.01, 1.15,]; P = 0.06) also had a borderline-significant association with decreased odds of an animal having a cross-contaminated hide. Although the prevalence of carcass contamination remains very low, targeted intervention at the preslaughter stage may have the potential to reduce further the risk to public health.

Source tracking of Escherichia coli O157:H7 and Salmonella contamination in the lairage environment at commercial U.S. beef processing plants and identification of an effective intervention

Transportation from the feedlot and lairage at the processing plant have been identified as potential sources of Escherichia coli O157:H7 and Salmonella hide contamination. The objective of this study was to perform a comprehensive tracking analysis of E. coli O157:H7 and Salmonella associated with beef cattle from the feedlot through processing. Cattle (n = 581) were sampled in a feedlot, then transported in multiple lots to three commercial, fed beef processing plants in the United States, where they were sampled again. Samples were collected from the tractor trailers prior to loading cattle and from the lairage environment spaces prior to entry of the study cattle. Pathogen prevalence on cattle hides increased on every lot of cattle between exiting the feedlot and beginning processing. Prior to loading cattle, E. coli O157:H7 was found in 9 (64%) of 14 tractor trailers. E. coli O157:H7 was detected in over 60% of the samples from each lairage environment area, while Salmonella was detected in over 70% of the samples from each lairage environment area. E. coli O157:H7 and Salmonella isolates (n = 3,645) were analyzed using pulsed-field gel electrophoresis. The results of the pulsed-field gel electrophoresis tracking indicate that the transfer of bacteria onto cattle hides that occurs in the lairage environments of U.S beef processing plants accounts for a larger proportion of the hide and carcass contamination than does the initial bacterial population found on the cattle exiting the feedlot. Finally, the results of this study indicate that hide wash cabinets are effective in removing contamination derived from the lairage environment.

The air-borne distribution of zoonotic agents from livestock waste spreading and microbiological risk to fresh produce from contaminated irrigation sources

AIMS

To assess the risks of zoonotic agents in dissemination of livestock wastes into the environment by airborne distribution. To subsequently assess the survival time of zoonotic agents, introduced in irrigation water, on the phylloplane of produce.

METHODS AND RESULTS

An Escherichia coli marker was introduced into pig slurry which was spread using a rain gun sprayer. Air sampling was undertaken to determine the distance reached by the marker. No recoveries were observed at a distance of 250 m. Borehole water, contaminated with zoonotic agents, was used to irrigate field plots sown with lettuce and spinach. Decline in bacterial numbers on the phylloplane was observed with time. After initial rapid decreases, we were unable to detect any pathogen from the phylloplane, 1 month after contamination.

CONCLUSIONS

These preliminary results suggest that the risks to public health from the aerosolized spread of bacteria during slurry spreading by rain gun are low. Although, zoonotic agents on crop phylloplanes perish quickly, the risks of overhead irrigation of fresh produce 3 weeks before harvest should still be considered.

SIGNIFICANCE AND IMPACT OF THE STUDY

These preliminary results improve our understanding on the fate of zoonotic agents in the environment. Spreading liquid livestock wastes by an airborne mechanism may not pose a significant public health risk. Detection of zoonotic agents 3 weeks after contamination of lettuce and spinach means that consideration should be given by the farmers until the time of harvest, when irrigating fresh produce with water that may have been directly or indirectly contaminated by livestock wastes.

Microbial populations on hides of grazing steers in a forage-based production system in Uruguay

The objective of the study was to evaluate the microbiological status of hides of grazing steers in a typical forage-based system in Uruguay. The study was conducted on a single farm with samples taken on 3 days during the spring of 2007. Four anatomical hide sites (perineum area, flank, back, and shoulder) of 10 steers were individually swabbed each sampling day at the farm environment (n = 120). Each sample was analyzed by the Laboratorio Tecnológico del Uruguay for aerobic plate counts (APC), total coliform counts (TCC), and Escherichia coli counts (ECC). Mean log values for APC, TCC, and ECC on external animal hide surfaces, across all sampling sites, were 5.52, 1.89, and 1.70 log CFU/cm2, respectively. There were no significant differences among bacterial counts from the four hide surface locations. Mean log values for APC, TCC, and ECC were 1.49, 1.15, and 1.12 log CFU/cm2 lower, respectively, on sampling day 2 than on sampling day 3. Microbial populations on hides of grazing steers are highly variable and dependent on climatic and environmental conditions. To our knowledge this is the first study published evaluating the hygienic conditions of grazing livestock operations in Uruguay and their potential implications on the red meat chain.

Occurrence of Escherichia coli O157 on hides of slaughtered cattle

AIMS

To obtain the first information on the occurrence of Escherichia coli O157 on hides of slaughtered cattle in Serbia.

METHODS AND RESULTS

A total of 355 swabs were taken on the slaughterline from five areas of hide of each of the 71 cattle in a single commercial abattoir in Serbia. Using an ISO method incorporating enrichment and immunomagnetic separation steps, E. coli O157 was isolated from the hides of 20 animals (28 x 2%). With respect to different areas of the hides, the occurrence of the pathogen was, in decreasing order: hooves (11 x 3%), brisket (8 x 4%), rump (7 x 0%), neck (4 x 2) and flank (2 x 8%). In addition, factors that had more or less effects on the occurrence included visible dirtiness of the hide, cattle's age category, geographical origin of the animals and season.

CONCLUSIONS

This study revealed the presence of E. coli O157 in the beef chain in Serbia and confirmed hide as an important potential source of related contamination of beef carcasses. Therefore, incorporation of preskinning hide decontamination treatments into HACCP-based slaughterline hygiene control measures could be very useful.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results will enable further optimization of necessary measures along the beef chain to reduce the E. coli O157 risks in Serbia.

Transportation and lairage environment effects on prevalence, numbers, and diversity of Escherichia coli O157:H7 on hides and carcasses of beef cattle at processing

Hide has been established as the main source of carcass contamination during cattle processing; therefore, it is crucial to minimize the amount of Escherichia coli O157:H7 on cattle hides before slaughter. Several potential sources of E. coli O157: H7 are encountered during transportation and in the lairage environment at beef-processing facilities that could increase the prevalence and numbers of E. coli O157:H7 on the hides of cattle. On three separate occasions, samples were obtained from cattle at the feedlot and again after cattle were stunned and exsanguinated at the processing plant (286 total animals). The prevalence of E. coli O157:H7 on hides increased from 50.3 to 94.4% between the time cattle were loaded onto tractor-trailers at the feedlot and the time hides were removed in the processing plant. Before transport, nine animals had E. coli O157:H7 in high numbers (> 0.4 CFU/cm2) on their hides. When sampled at the slaughter facility, the number of animals with high hide numbers had increased to 70. Overall, only 29% of the E. coli O157:H7 isolates collected postharvest (221 of 764) matched pulsed-field gel electrophoresis types collected before transport. The results of this study indicate that transport to and lairage at processing plants can lead to increases in the prevalence and degree of E. coli O157:H7 contamination on hides and the number of E. coli O157:H7 pulsed-field gel electrophoresis types associated with the animals. More study is needed to confirm the mechanism by which additional E. coli O157:H7 strains contaminate cattle hides during transport and lairage and to design interventions to prevent this contamination.

Validation of time and temperature values as critical limits for the control of Escherichia coli O157:H7 during the production of fresh ground beef

In order to provide beef processors with valuable data to validate critical limits set for temperature during grinding, a study was conducted to determine Escherichia coli o157:H7 growth at various temperatures in raw ground beef. Fresh ground beef samples were inoculated with a cocktail mixture of streptomycin-resistant E. coli O157:H7 to facilitate recovery in the presence of background flora. Samples were held at 4.4, 7.2, and 10 degrees C, and at room temperature (22.2 to 23.3 degrees C) to mimic typical processing and holding temperatures observed in meat processing environments. E. coli O157:H7 counts were determined by direct plating onto tryptic soy agar with streptomycin (1,000 microg/ml), at 2-h intervals over 12 h for samples held at room temperature. Samples held under refrigeration temperatures were sampled at 4, 8, 12, 24, 48, and 72 h. Less than one log of E. coli O157:H7 growth was observed at 48 h for samples held at 10 degrees C. Samples held at 4.4 and 7.2 degrees C showed less than one log of E. coli O157:H7 growth at 72 h. Samples held at room temperature showed no significant increase in E. coli O157:H7 counts for the first 6 h, but increased significantly afterwards. These results illustrate that meat processors can utilize a variety of time and temperature combinations as critical limits in their hazard analysis critical control point plans to minimize E. coli O157:H7 growth during the production and storage of ground beef.