Unveiling contamination sources and dissemination routes of Salmonella sp. in pigs at a Portuguese slaughterhouse through macrorestriction profiling by pulsed-field gel electrophoresis

Sixty-nine isolates of Salmonella sp. isolated from the ileum, tonsils, carcass and mandibular and ileocolic lymph nodes of individual pigs slaughtered for consumption in one abattoir were analyzed using serotyping and macrorestriction profiling by Pulsed-Field Gel Electrophoresis (RFLP-PFGE), in order to identify clonal relationships. XbaI macrorestriction was able to distinguish 18 genotypes among the eight identified serotypes: Salmonella Typhimurium (4 genotypes), Salmonella Rissen (3), Salmonella Tennessee (2), Salmonella Enteritidis (2), Salmonella 4,[5],12:i:- (4), Salmonella Give (1), Salmonella Anatum (1), and Salmonella Derby (1). Except for one sample, the serotype and the genotype identified in the samples from the same pork were always the same, allowing to unravel possible dissemination routes of Salmonella sp. through these pork tissues and equate presumptive sources of contamination or infection. Highly significant associations (p < 0.001) were observed for the presence of Salmonella sp. in the ileum and in the ileocolic lymph nodes, as well as between the carcass contamination and the presence of Salmonella sp. in others samples of the correspondent slaughtered pig, such as the ileum, the ileocolic and mandibular lymph nodes and the tonsils. Moreover, 80% of the pigs with ileum and ileocolic lymph nodes positive samples also presented the same salmonella genotype in the correspondent tonsils and, among pigs with positive tonsils, 70% also carried the same genotype in the corresponding mandibular lymph nodes. The occurrence of cross-contamination was also detected, since a genotype identified in other pigs slaughtered in the same day was found in 31% of positive carcasses. The global analysis of the genotypes suggested three different sources of pig infection: the farm of origin, the transportation and the lairage. A particular attention should be paid to the last one, since the majority of the isolates from pig samples were related to infection in the lairage. Since the presence of Salmonella sp. in the ileum of pigs and faeces ingestion promotes tonsils infection and internal dissemination of the agent through the mandibular lymph nodes, as well as drainage to the ileocolic lymph nodes, a potential risk exists at slaughter for Salmonella sp. contamination in the carcasses during pork processing. This risk may be increased by incorrect evisceration techniques and by hygienically inappropriate meat inspection procedures, especially those concerned to the mandibular lymph nodes incisions.     

Tracking the Salmonella status of pigs and pork from lairage through the slaughter process in the Republic of Ireland

Salmonella Typhimurium is the predominant serotype isolated from humans in Europe. Pork and pork products are recognized vehicles of Salmonella and are responsible for outbreaks of human salmonellosis. Pigs can become infected with Salmonella on the breeding or fattening farm and during transport, lairage, and slaughter. The aim of this study was to investigate selected points of Salmonella contamination from the time pigs entered the lairage to the time the carcass was processed in the boning hall and to determine the importance of different sources of Salmonella along the Irish pork production chain. A second objective was to evaluate whether the serological status or category of a herd influenced the levels of bacteriological contamination detected on individual carcasses and pork cuts during slaughter and dressing operations. All samples were tested for the presence and numbers of Salmonella. Enterobacteriaceae numbers were also determined. Serotype, phage type, and pulsed-field gel electrophoresis were utilized to determine similarity among Salmonella isolates. Lairage was a major source of cross-contamination with Salmonella as were the hands of evisceration operatives, conveyor belts, and equipment in the boning hall. Cross-contamination within the slaughter plant environment accounted for up to 69 % of Salmonella carcass contamination. In general, herd category reflected the bacteriological status of carcasses and pork cuts. Major findings were a strong association (P < 0.01) between Enterobacteriaceae counts and Salmonella occurrence on prechill carcasses and a significant association (P < 0.05) between Enterobacteriaceae counts and Salmonella occurrence on pork cut samples.     

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.     

Longitudinal Dissemination of Salmonella enterica Clonal Groups through the Slaughter Process of Salmonella-Positive Pig Batches

This study was conducted to assess the dissemination of Salmonella clonal groups in slaughterhouses that received batches of Salmonella -positive pigs and used different routine processing procedures. Eight serial sampling sessions were conducted in three slaughterhouses (A, B, and C). Blood was collected randomly (n = 25) from each batch of pigs and processed for serology. Carcasses (n = 12) were identified and sampled after dehairing, after singeing, after evisceration, and before chilling. A section of cecum also was collected. Salmonella isolates were submitted to pulsed-field gel electrophoresis. The overall seroprevalence of Salmonella was 80.6% (316 of 392 samples), and cecal contents were positive for Salmonella in 23.8% (26 of 109) of the pigs sampled. Carcasses after dehairing had a significantly higher prevalence of Salmonella (P = 0.004) and the highest Salmonella levels (median ～ 0.26 log CFU/300 cm(2)). The singeing step significantly affected the Salmonella status of the carcasses (P = 0.001); however, the efficacy of singeing differed among slaughterhouses. In the prechilling step, 14.7% (16 of 109) of the carcasses were positive for Salmonella. Salmonella pulsotypes found on the prechill carcasses were also found in the lairage, in the cecal contents, and on carcasses after dehairing, suggesting that the main source of contamination was the slaughter process before singeing. Slaughterhouse C was the most likely (odds ration [OR] ～ 6.51) to have pigs carrying Salmonella in the gut, and slaughterhouse B was the most likely (OR ～ 14.66) to have contaminated carcasses at the prechilling step. These findings indicate that the procedures adopted in slaughterhouse B contributed to the spread of Salmonella strains. In contrast, in slaughterhouse C the Salmonella strains carried by the pigs or found in the lairage were not recovered from prechilled carcasses, validating the effectiveness of the slaughterhouse interventions. These results indicate that an effective slaughter process can help decrease the number of Salmonella-positive carcasses in slaughterhouses that receive Salmonella-positive pig batches.     

Detection and characterization of Salmonella in lairage, on pig carcasses and intestines in five slaughterhouses

In this study, conducted at five slaughterhouses, individual pigs were sampled and followed up from stunning to cooling down of the carcasses. In this way, Salmonella prevalence and possible risk points were described. At the lairage area, pens were sampled using overshoes. At stunning and bleeding, pigs were individually identified and subsequently swabs were taken of the oral cavity and the carcass after polishing, splitting and forced chilling. Additionally, duodenum, ileum, rectum and mesenteric lymph nodes were extracted and samples were taken of the scalding water. All samples were submitted to Salmonella isolation and Salmonella isolates were serotyped and genotyped by pulsed-field gel electrophoresis (PFGE). Of all samples taken (n = 1953), 14.1% were Salmonella positive. The prevalence of S. in the lairage area varied widely (from 0 to 100%) between the slaughterhouses. Of the sampled pigs (n = 226), 48.2% were positive in at least one sample. Statistical analysis revealed that the contamination of the lairage area was related to a higher amount of positive carcasses after polishing. Furthermore, the contamination of the carcasses after splitting and forced chilling was related to the contamination level of the carcass after polishing. A relation between the outer (carcass) contamination and the inner (gut content and lymph nodes) contamination of a pig could not be established. The predominant serotypes were S. Typhimurium (58.7%) and S. Derby (17.4%). Genotyping revealed 46 different PFGE profiles among the 276 Salmonella isolates. The same genotype at the lairage area as in the oral cavity of the pigs was found in 95%. The results indicate that the lairage area is a primary source of Salmonella in slaughter pigs and that carcass contamination originates from the environment rather than from the pig (inner contamination) itself. It further shows that slaughterhouses vary in their capability of dealing with Salmonella positive pigs. A slaughterhouse specific approach is needed, however, general guidelines should be provided to decrease the contamination level of the lairage area and the slaughter environment.     

Microbial profiles of carcasses and minced meat from kangaroos processed in South Australia

The microbiological profiles of kangaroo carcasses and minced meat at game meat processing plants in South Australia were determined in surveys undertaken in 2002 and 2004. In 2002 mean values for log(10) total viable counts (TVC) on carcasses at individual plants ranged from 0.9 to 3.9 log(10) cfu/cm(2), with the mean for all plants being 2.3 log(10) cfu/cm(2). In 2004 the between plant range was narrower, by about 1 log unit, and the mean value for carcasses at all plants was 1.2 log(10) cfu/cm(2). Minced kangaroo meat, was sampled in 2002 only. The overall mean log(10) TVC was 3.9 log(10) cfu/g, with mean counts at individual plants ranging from 3.1 to 4.6 log(10) cfu/g. The overall prevalence of E. coli was 70%, with mean numbers of 2.1 log(10) cfu/g on positive samples. Salmonella was not detected in any of 60 samples from carcasses in 2002. However, in 2004 Salmonella was detected in 4/385 samples (1.04%, 95% CI: 0.28%-2.64%). In minced kangaroo meat, Salmonella was detected in 9/50 (18%, 95% CI: 9%-31%) samples. The abdominal cavity, sampled in 2004, was found to be highly contaminated, with E. coli isolated from 46% of samples and the mean number for positive samples being 2.7 log(10) cfu/cm(2); Salmonella was isolated from 14/120 (12%; 95% CI: 6.52%-18.80%) of abdominal cavities. The practice of collecting carcasses together and pushing grouped carcasses into the chiller likely leads to cross contamination of carcasses from the abdominal cavities of others. To align results of sampling by swabbing for domestic purposes with excision sampling, required for export purposes, both methods were used to sample opposite sides of each of the 50 carcasses sampled in 2004. The results obtained with the two methods of sampling were similar.     

Salmonella in slaughter pigs in Northern Ireland: prevalence and use of statistical modelling to investigate sample and abattoir effects

A cross-sectional survey of pigs at slaughter in Northern Ireland was undertaken to determine the overall prevalence of Salmonella infection. In total 513 pigs were sampled across four abattoirs, with Salmonella spp. isolated from the caecal contents of 31.4% (95% confidence interval [CI] 27.4%-35.4%) and from 40.0% (95% CI 35.8%-44.3%) of swabs taken from the surface of carcasses post-evisceration. Two serovars, S. Typhimurium and S. Derby, were predominant and accounted for 52% and 35% respectively, of isolates from caecal contents. Antimicrobial resistance was most common amongst isolates of S. Typhimurium with 63.9% multiresistant compared to 10.8% of S. Derby isolates and 8.0% of other Salmonella spp. The proportion of pigs showing serological evidence of infection was significantly lower, with 11.5% (95% CI 8.9%-14.6%) and 10.1% (95% CI 7.7%-13.1%) of meat-juice samples giving positive and suspect reactions, respectively. The ratio of caecal positive to serologically positive animals is higher than in a number of other studies and may suggest recent infection, such as infection occurring during transport or lairage, in a proportion of animals. Statistical (logistic regression) modelling was used to investigate the association between the risk of Salmonella on carcasses and the isolation of Salmonella from caecal contents, and/or the serological status of the animal, while adjusting for other possible explanatory and confounding variables such as abattoir, season, day and time of sampling. The occurrence of Salmonella in caecal contents (odds ratio [OR] 2.39; 95% CI 1.52-3.77) or a suspect/positive serological reaction (OR 2.15; 95% CI 1.28-3.61) were both independently associated with the occurrence of Salmonella on carcasses in homebred, but interestingly not in imported animals. In most multivariable models there were also significant differences in carcass contamination between seasons with the highest odds of carcass contamination occurring in the April to June quarter and the lowest in the October to December quarter. Differences between sampling days were also evident with the highest odds of carcass contamination at the end of the week (Fridays) and the lowest at the start of the week (Mondays). These associations, after adjusting for the caecal or serological result, would suggest the occurrence of abattoir effects, such varying residual levels of abattoir contamination, which are independent of the individual pig status.     

Belgian surveillance plans to assess changes in Salmonella prevalence in meat at different production stages

From 1997 to 1999, the prevalence of Salmonella was assessed at different stages through the pork, poultry, and beef meat production chains. Different dilutions of the initial sample suspension were analyzed to provide a semiquantitative evaluation of Salmonella contamination and to determine the most representative dilution necessary to detect a reduction in prevalence. An average of 300 samples for each type of meat were analyzed. According to Fisher's exact test, the dilution to be used to detect a reduction in prevalence was chosen based on an initial prevalence of 20 to 26%. Based on this introductory study, a new sampling plan representative of the nationwide Belgian meat production process was used from 2000 through to 2003. This study confirmed the consistently high rate and level of contamination of poultry meat: broiler and layer carcasses were the most contaminated samples followed by broiler fillets and poultry meat preparations. A constant and significant decrease in Salmonella prevalence was observed for pork carcasses, trimmings, and minced meat and for beef minced meat. Less than 3% of beef carcasses and trimming samples were positive for Salmonella. The Belgian plan, as utilized from 2000 to 2003, was suitable for monitoring of zoonoses because the sampling plan was representative of nationwide production processes, covered all periods of the year, and was executed by trained samplers and the analyses were carried out by recognized laboratories using an identical analytical method.     

Tracking the sources of salmonella in ground beef produced from nonfed cattle

The objective of this study was to determine the source(s) of Salmonella contamination in ground beef. One hundred dairy cows were harvested in a U.S. commercial beef processing plant. Samples of hides, carcasses after hide removal and before exposure to antimicrobial intervention, carcasses after all antimicrobial interventions, superficial cervical lymph nodes from the chuck, trim, ground beef, and air were obtained. Ninety-six percent of the hide samples, 47% of the carcasses before intervention, 18% of the lymph nodes, 7.14% of the trim, and 1.67% of the ground beef samples were positive for Salmonella. None of the samples obtained from the carcasses after the full complement of interventions and none of the air samples were positive for Salmonella. All Salmonella-positive samples were subjected to pulsed-field gel electrophoresis, and eight DNA Xba I restriction patterns were identified. The majority of isolates had one of two restriction digest patterns. The strain isolated from ground beef had the same pattern as the strains isolated from hides and from carcasses immediately after hide removal. The Salmonella isolates from trim samples and lymph nodes also had the same restriction digest pattern. These results indicate that hide and lymph nodes are the most likely sources of Salmonella in ground beef. Dressing practices that effectively reduce or eliminate the transfer of bacteria from hide to carcass and elimination of lymph nodes as a component of raw ground beef should be considered as measures to reduce Salmonella contamination of ground beef. Because total elimination of lymph nodes from ground beef is not possible, other approaches should be explored. Easily accessible lymph nodes could be screened for Salmonella very early in the slaughter process. When the results are positive for Salmonella, the corresponding carcasses should be fabricated separately at the end of the production run, and the trim from these carcasses should be subjected to a treatment that destroys Salmonella.     

A longitudinal study of Salmonella and Campylobacter jejuni isolates from day of hatch through processing by automated ribotyping

Comparisons of bacterial populations over long periods of time allow researchers to identify clonal populations, perhaps those responsible for contamination of farms or humans. Salmonella and Campylobacter can cause human illness, and our objective was to use a library typing system to track strains that persist in the poultry house and through the processing plant. Two farms, over four consecutive flocks, were studied. Multiple samples were taken of the poultry house environment, feed mill, transport crates, and carcasses in the processing plant. Sample collection on the farm took place on chick placement day, midgrowout, and the day of harvest. This study found that 80.3% of isolates belonged to a single strain of Salmonella Kentucky that persisted in several environmental samples for all flocks at both farms, from chick placement day to the final product at the plant. Surgical shoe covers produced most isolates (n = 26), and processing day yielded the highest recovery (n = 68). Additional serotypes were recovered, but the Salmonella Kentucky-positive eggshells and chick mortality appeared to be the source of the organism for both farms. All Campylobacter isolates recovered were identified as C. jejuni. Most Campylobacter isolates (90.1%) belonged to one of three core strains. C. jejuni was not recovered on chick placement day. Cecal droppings yielded all nine strains. Most isolates (98.2%) were from one farm. Cluster analysis grouped C. jejuni and Salmonella isolates into four and six distinct clusters, respectively, on the basis of a similarity level of 80%.     

Incidence of Salmonella, Campylobacter jejuni, Campylobacter coli, and Listeria monocytogenes in poultry carcasses and different types of poultry products for sale on the Belgian retail market.

From January 1997 to May 1998, 772 samples of poultry carcasses and poultry products for sale on the retail market in Belgium were analyzed for the presence of Salmonella spp., Salmonella Enteritidis, Campylobacter jejuni, C. coli, and Listeria monocytogenes per 100 cm2 or 25 g. Poultry samples were contaminated with Salmonella (36.5%), C. jejuni and C. coli (28.5%), and L. monocytogenes (38.2%). In about 12.3% of the poultry samples, the L. monocytogenes contamination level exceeded 1 CFU per g or cm2. Significant differences in pathogen contamination rates of poultry products were noticed between the poultry products originating from Belgian, French, and U.K. abattoirs. Poultry products derived from broiler chickens running free in pine woods until slaughtering age (12 to 13 weeks) had a significantly (P < 0.05) lower contamination rate of Salmonella than poultry products from enclosed broilers slaughtered at the age of 6 to 8 weeks. A significantly (P < 0.05) lower pathogen contamination rate was noted for Salmonella, C. jejuni, and C. coli for poultry cuts without skin compared to poultry cuts with skin on. An increase in pathogen contamination rate was noticed during cutting and further processing. To diminish C. jejuni, C. coli, Salmonella, and L. monocytogenes contamination rates, hygienic rules of slaughter and meat processing must be rigorously observed. At the moment, zero tolerance for these pathogens is not feasible, and there is a need to establish criteria allowing these pathogens to be present at reasonable levels in the examined poultry samples.     

Prevalence of Salmonella and Campylobacter in beef cattle from transport to slaughter

The objective of this study was to evaluate the effect of typical production practices during the transport of cattle on the resulting incidence of Salmonella and Campylobacter in the feces, on the hides, and on the carcasses of these cattle and in the environment (trucks, holding pens, and knock boxes). Various factors were evaluated, including the type of animal (feedlot cattle vs. adult pasture cattle), the breed of cattle, the body condition of the animal, the age of the animal, the time of feed and water withdrawal, the contamination level of the transport vehicle at the feedlot or farm, the transport time, the time cattle were held in the holding pen at the plant, and the contamination level of the holding pen. Four groups of each type of animal were sampled on different days. Samples were collected from cattle prior to transport and after transport (rectal and hide swabs) as well as from the carcasses of these cattle. Pre- and posttransit samples were also taken from the transport vehicle and from the holding pen and knock box at the slaughter facility. For feedlot cattle, fecal shedding stayed fairly constant for both organisms before and after transport (3 to 5% for Salmonella and 64 to 68% for Campylobacter). However, the shedding rate for adult cattle increased from 1 to 21% for Salmonella but stayed constant for Campylobacter (6 to 7%). Contamination of hides with Salmonella increased for both animal types from a level of 18 to 20% to a level 50 to 56%. For Campylobacter, the contamination level decreased from 25 to 13% for feedlot cattle but remained unchanged for adult animals (1 to 2%). Nineteen percent of feedlot cattle carcasses and 54% of adult cattle carcasses tested positive for Salmonella, while only2% of feedlot cattle carcasses and none of the adult cattle carcasses tested positive for Campylobacter. Thus, for feedlot cattle, the factors considered in this study did not affect the shedding of either organism but did affect the contamination of hides with both. For adult animals, the factors increased both shedding of and hide contamination with Salmonella only, not Campylobacter.     

Salmonella in the lairage of pig slaughterhouses

The purpose of this study was to determine if lairages of pig slaughterhouses can act as a source of contamination of slaughtered pigs with Salmonella. The prevalence and variety of serotypes of Salmonella in the lairages of two pig slaughterhouses were determined, and the efficacy of the usual cleaning and disinfection on the presence of Salmonella was estimated. Lairages of two pig slaughterhouses were sampled three times when pigs were present. Furthermore, these lairages were sampled after the usual cleaning and disinfection, whereas the lairage of one slaughterhouse was sampled an additional time after improved cleaning and disinfection. Samples were collected by swabbing floor and wall surfaces and collecting the residing fluids on the floor throughout the lairage. Salmonella was isolated in 70 to 90% of the samples when pigs were present. The usual cleaning and disinfection reduced the level of contamination with Salmonella to 25% positive samples, whereas improved cleaning and disinfection reduced this level to 10% positive samples. It is concluded that the waiting period in the lairage of at least 2 h contains a substantial risk for slaughter pigs to become infected with Salmonella, especially for pigs originating from Salmonella-free herds. The usual cleaning and disinfection of the lairage were not sufficient to eliminate this risk, whereas an improved procedure for cleaning and disinfection still was unsatisfactory.     

Bacteriological safety issues in red meat and ready-to-eat meat products, as well as control measures

The importance of Eschericha coli O157, Listeria monocytogenes and Salmonella typhimurium DT104 as meat-borne pathogens is well established. Pathogenic bacteria such as Aeromonas spp., Arcobacter spp., psychrotrophic Bacillus cereus, Campylobacter spp., Clostridium botulinum and non-invasive Listeria monocytogenes can be regarded as rookies, but not yet firmly associated with today's production of red meat and meat products. The development of PCR and other DNA-based techniques will shed new light on so called emerging pathogens. Important safety issues in meat production, such as insufficient cleaning and disinfection (including the stable/lairage, processing environment), carcass decontamination and chilling, and cross contamination are discussed. Furthermore, probability modelling of survival and growth is identified as an important way to achieve a better understanding of how to deal with the complexity of further processing, including heat treatment and storage.     

Microbial contamination of carcasses, meat, and equipment from an Iberian pork cutting plant

An assessment and follow-up of the microbial contamination of an Iberian pork cutting room is presented. Samples were taken from carcasses (n = 76), meat pieces (three types, n = 71), meat for dry-cured sausages (3 types, n = 66), and surfaces of equipment (n = 158). Aerobic plate counts (APC) at 37 degrees C on meat pieces (primal cuts) were lower than on carcasses (3.62 log CFU/10 cm2 against 4.63 log CFU/10 cm2), probably owing to the removal of the skin. However, more than 80% of the meat pieces showed presence of Escherichia coli. For the three types of meat intended for dry-cured sausages, higher counts (P < 0.001) were found for meat type 3--an important cut obtained from the vertebral column--at 2.62 log CFU/g for E. coli; the particular surface used in the handling of meat type 3 also showed high counts (P < 0.001) for E. coli. Consequently, attention should be paid to the hazard analysis critical control point plan at this stage. Salmonella was isolated from 3.94% of the carcass surfaces (perianal zone), 4.46% of meat pieces, and 13.58% of meat for dry-cured sausages. Moreover, the percentages for isolation of Salmonella from carcasses of Iberian pigs (extensive rearing) in our study were lower than those generally reported in the literature for "white pigs" (intensive rearing). Coagulase-positive Staphylococcus aureus was isolated in 31.82% of meat samples for dry-cured sausages, in 16.90% of meat pieces, and in 15.50% of the equipment after 4 h of work. Of the coagulase-positive strains isolated, 47.61% were producers of enterotoxin.     

Visible contamination on animals and carcasses and the microbiological condition of meat

It is generally assumed that preventing visible contamination of or removing visible contamination from carcasses will enhance the microbiological safety of meat. Visible contamination of carcasses can be reduced by washing or otherwise cleaning animals before slaughter, by dehairing hides before carcasses are skinned or dressed with the skin on, or by performing skinning and eviscerating operations in manners that avoid the transfer of filth from the hide to the meat or the spillage of gut contents. Visible contamination can be removed by washing, trimming, or vacuuming carcasses. The available data appear to indicate that, of the various actions that can be taken to obtain carcasses that are free of visible contamination, only minimizing the visible contamination of meat during skinning and eviscerating operations may also ensure a degree of control over the microbiological contamination of meat. It might be preferable for visible contamination to be controlled largely by superior skinning and eviscerating practices rather than by animal or carcass cleaning treatments, which may not prevent the depositing of bacteria on or the removal of substantial numbers of bacteria from carcasses.     

Contamination of chicken carcasses in Gauteng, South Africa, by Salmonella, Listeria monocytogenes and Campylobacter

The presence of the foodborne pathogens, Salmonella spp., Listeria monocytogenes and Campylobacter spp., on 99 fresh and frozen chicken carcasses sourced from various retailers in Gauteng, South Africa, was investigated. Using culture methods, 60.6% of the carcasses were found to be contaminated with one or more pathogens, with 19.2%, 19.2% and 32.3% of the carcasses being found to harbour Salmonella, L. monocytogenes and Campylobacter, respectively. The extent of contamination with one or more pathogens was not significantly different (p>0.1) between fresh or frozen samples or between samples from butcheries, supermarkets or street vendors. Significantly more (p<0.1) fresh carcasses from butcheries than from other outlets were contaminated with Salmonella, while more fresh carcasses from supermarkets were contaminated with Campylobacter. The proportion of carcasses with L. monocytogenes from all sources were similar. Polymerase chain reaction (PCR) results indicate an even higher extent of pathogen contamination, but the PCR techniques need to be further refined before they can be used routinely.     

Microbiological quality of Australian beef

A survey of the microbiological quality of beef carcasses and boneless beef produced in Australia was conducted during the period June to November 1998. Sponge samples were collected from 1,275 carcasses, and meat samples were drilled from 990 cartons of frozen boneless beef. Carcass and boneless beef samples were respectively collected from 21 and 27 establishments that concentrated on export and from 38 and 3 establishments supplying the Australian domestic market of which 31 were very small plants slaughtering no more than 150 cattle equivalents per week. The mean log total viable counts (TVCs) were 2.42/cm2 and 2.52/g for carcasses and boneless meat, respectively. Escherichia coli was detected on 10.3% of carcasses and 5.1% of boneless beef samples and coagulase-positive staphylococci on 24.3% of carcasses and 17.5% of boneless beef. Salmonella was detected on 0.2% of carcasses and 0.1% of boneless beef and E. coli O157:H7 recovered from 0.1% of carcasses but not detected on 990 boneless beef samples. Mean log TVCs/cm2 differed significantly (P < 0.05) between establishment types. They were lower on carcasses from export establishments (2.20) compared with domestic (2.61) and very small plants (3.10). There were no significant differences in prevalence of Salmonella or E. coli O157:H7 between establishment types. Excision samples were taken from 670 carcasses to make comparisons with the first baseline study of Australian meat, carried out in 1993 to 1994. While there were differences in sampling and microbiological techniques between the two studies that require detailed consideration, there were small but significant improvements in several microbiological criteria for carcasses and boneless meat.     

Microbiological quality of Australian sheep meat

Microbiological quality of sheep carcasses and boneless sheep meat produced in Australia was surveyed during the period June to November 1998. Sponge samples were collected from 917 carcasses, and meat samples were drilled from 467 cartons of frozen boneless meat. Carcass and boneless meat samples were respectively collected from 7 and 10 establishments that concentrated on export, and from 36 and 5 establishments supplying the Australian domestic market of which 31 were very small plants slaughtering cattle and sheep but no more than 1,200 sheep equivalents per week. The mean log total viable counts were 3.55/cm2 and 3.30/g for carcasses and boneless meat, respectively. Escherichia coli was detected on 29.2% of carcasses and 24.5% of boneless meat samples and coagulase-positive staphylococci on 24.1% of carcasses, and 38.6% of boneless meat samples. Salmonella was detected on 0.1% of carcasses and 1.3% of boneless meat samples. E. coli O157:H7 was recovered from 0.7% of carcasses and 1.3% of boneless sheep meat. There were statistically significant differences between establishment types for some microbiological criteria, although there were no significant differences in prevalence of Salmonella or E. coli O157:H7 between establishment types. While there were differences in sampling and microbiological techniques between this study and another conducted in 1993 to 1994 that require detailed consideration, there were small but significant improvements in several microbiological criteria for boneless meat. While data that would allow for comparison of carcass data were not gathered, it is unlikely that improvements in the microbiological quality of boneless sheep meat could accrue without improvements to carcasses.     

A study of the prevalence and enumeration of Salmonella enterica in cattle and on carcasses during processing

Salmonella prevalence and counts were estimated for samples from the oral cavity, hide, rumen, and feces of 100 cattle at slaughter and from the pre- and postchill carcasses of these cattle. Samples were collected from 25 consecutively slaughtered cattle from each of four unrelated groups slaughtered at a single abattoir on different days. Ten additional fecal samples from each group were collected from their respective abattoir holding pens prior to slaughter. The prevalence of Salmonella was estimated using automated immunomagnetic separation, and the counts were estimated using a combination of most probable number (MPN) and automated immunomagnetic separation. A total of 606 samples were collected with Salmonella isolated from 157 (26%), including 29% of oral cavities, 68% of hides, 16% of feces collected after evisceration, 25% of rumen samples, 2% of prechill carcasses, 3% of postchill carcasses, and 48% of feces collected from holding pens. The prevalence and count of Salmonella varied between the different groups of animals tested. The highest count obtained was from a rumen sample (1.1 x 10(4) MPN/g). Other counts were generally low, with a maximum count in feces collected after evisceration and in the abattoir holding pens of 93 and 23 MPN/g, respectively. The highest count on hides, in oral cavities, and on carcasses was 4.8 MPN/cm2, 23 MPN/g, and 0.31 MPN/cm2, respectively. Even though Salmonella was present on the hides and in the rumen and feces of at least one animal from each group of cattle, the processing of animals at this abattoir resulted in few contaminated carcasses, and when contamination occurred, Salmonella was detected at low numbers.