Pluck Set Research Articles

Views of veterinarians and meat inspectors concerning the practical application of visual meat inspection on domestic pigs in Finland

The post-mortem inspection of domestic pigs within the European Union was revised in 2014, primarily to include visual meat inspection of each carcase and offal. Palpations and incisions were removed from routine meat inspection procedures, as they are mostly used to detect pathological lesions caused by organisms irrelevant for public health, and instead can cause cross-contamination of carcases with foodborne pathogens. However, examination of all external surfaces of the carcase and organs, declaration of patho-physiological lesions as unfit for human consumption, and possibility for minimal handling of carcases and offals were held in place. In addition, the European Food Safety Authority suggested that palpation and incisions should be performed outside the slaughter line, but this was not incorporated in the revised legislation. We surveyed in 2014 the opinions of meat inspectors and veterinarians using an online questionnaire to determine what practical measures are required for the visual meat inspection procedure and when meat inspection staff consider additional palpations and incisions necessary. Based on the survey, turning the carcase and organs or technical arrangements such as mirrors were seen necessary to view all external surfaces. In addition, the pluck set cannot be trimmed on the side line. Local lesions, such as abscesses and lesions in the lymph nodes, signs of systemic infection and lymphoma, were the major lesions requiring additional post-mortem meat inspection procedures. Meat inspection personnel raised concerns on the poor quality of food chain information and export requirements demanding palpations and incisions. The efficient use of visual meat inspection requires legislation to better support the implementation and application of it, changes in the slaughter line layout and a possibility to classify incoming pig batches based on their risk.

Reduced contamination of pig carcasses using an alternative pluck set removal procedure during slaughter

This study compared the current pig slaughter procedure where the pluck set is completely removed with a procedure where the pluck set is partially removed, leaving the highly contaminated oral cavity, tonsils and tongue untouched. The effect on carcass contamination was investigated by enumerating hygiene indicator bacteria (total aerobic count, Enterobacteriaceae and E. coli) and cefotaxime-resistant E. coli (CREC) as well as assessing Salmonella and Yersinia enterocolitica presence on the sternum, elbow and throat of pig carcasses. Using the alternative pluck set removal, significantly lower mean numbers of hygiene indicator bacteria on throat samples and E. coli on elbow samples were found. Less pig carcasses were highly contaminated and a lower presence and level of CREC was observed. No difference in Salmonella or Yersinia enterocolitica presence was seen. The data in this study can help to assess the effect of this alternative procedure on the safety of pork and subsequently public health.

Bayesian modelling to identify the risk factors for Yersinia enterocolitica contamination of pork carcasses and pluck sets in slaughterhouses

The probability of contamination by pathogenic Yersinia enterocolitica of carcasses and pluck sets at slaughterhouse was determined by means of a Bayesian analysis. Prior information of the prevalence of Y. enterocolitica in faeces and the seroprevalence of Yersinia in serum of pigs collected at farms were obtained from previous studies and introduced in the models as beta prior informative distributions. Samples of intestinal content, tonsils, and swabs of carcasses and pluck set surfaces were collected at slaughterhouses. The posterior probabilities, odds ratio (OR) and their probability interval (PI) were calculated by means of a generalized linear model constructed in WinBugs. Occurrence of Y. enterocolitica in intestinal content (OR: 35.6, 95%PI 2.8–8285), tonsils (OR: 38.4, 95%PI 5.0–854), and pluck set (OR: 16.6, 95%PI 1.9–1111) was a risk for the contamination of pork carcasses, and an increased risk of contaminated pluck set was observed when Y. enterocolitica was isolated in intestinal content (OR: 40.6, 95%PI 2.1–10510) and tonsils (OR: 17.6, 95%PI 3.4–230.6). This increased risk indicated a potential cross-contamination at the slaughterhouse.

Detection, enumeration and characterization of Yersinia enterocolitica 4/O:3 in pig tonsils at slaughter in Northern Italy

Tonsils from 150 pigs slaughtered at 270days or older were tested for Yersinia enterocolitica with different cultural methods. Samples were collected in three different abattoirs of Northern Italy between April and November 2012 and were analysed by direct plating on cefsulodin–irgasan–novobiocin (CIN) agar and by enrichment procedures following the ISO 10273:2003 reference method. Twenty-three (15.3%) samples were positive: 22 tonsils (14.7%) were positive for human pathogenic Y. enterocolitica bio-serotype 4/O:3 and one tonsil (0.7%) for Y. enterocolitica bio-serotype 1A/7,8-8,8,19. Seventeen samples out of 23 (73.9%) were positive by direct plating method. Among the enrichment procedures, the best recovery rate (8 positives out of 23; 34.8%) was obtained by the two-day enrichment in peptone–sorbitol–bile (PSB) broth followed by plating on CIN agar plates. The two-day enrichment in PSB followed by potassium hydroxide (KOH) treatment before plating onto CIN agar gave 7 positives out of 23 (30.4%), decreasing to 3 positives (13.0%) without KOH treatment. The worst results were obtained by prolonged (five days) enrichment in PSB, with or without KOH treatment, followed by plating on CIN agar: 4.3% (1 out of 23) and 0.0% recovery rates, respectively. The mean concentration was 1.9×104CFU/g, with a minimum of 1.0×102CFU/g and a maximum of 5.8×104CFU/g, thus demonstrating that tonsils may play an important role in contamination of pluck sets, carcasses, and slaughterhouse environment.Prevalence of virulence genes among the Y. enterocolitica 4/O:3 isolates was as follows: 12/22 (54.5%) for yadA, 21/22 (95.5%) for ail, 21/22 (95.5%) for inv and 22/22 (100%) for ystA.All Y. enterocolitica 4/O:3 isolates were sensitive to amoxicillin/clavulanic acid, ciprofloxacin and ceftazidime and resistant to ampicillin and cephalotin. High proportions of 4/O:3 isolates (95%) were sensitive to cefotaxime, gentamicin, kanamicin and nalidixic acid. High levels of resistance were observed to sulphonamide compounds (91%), streptomycin (64%) and chloramphenicol (55%). Multi-resistant isolates were very common; resistance to three or more antimicrobials was observed in 91% (20/22) of 4/O:3 isolates. High level of resistance to chloramphenicol was possibly due to coresistance to tiamphenicol, which was detected in 100% of the isolates.XbaI-PFGE detected four clusters among the 22 Y. enterocolitica 4/O:3 isolates. The most represented accounted for 77% (17/22) of the isolates, the second most common was found in 14% (3/22) of the isolates and the two other profiles were observed in single isolates. The comparison with a selection of human isolates supported the role of the pig as reservoir of 4/O:3 Y. enterocolitica.

Listeria monocytogenes Contamination in Pork Can Originate from Farms

The presence of Listeria monocytogenes in the pork production chain was followed from farm to slaughterhouse by examining the farm and slaughterhouse levels in the same 364 pigs, and finally by analyzing the cut meats from the same pig lots. Both organic and conventional farms were included in the study. Altogether, 1,962 samples were collected, and the 424 L. monocytogenes isolates were analyzed by pulsed-field gel electrophoresis. The results from microbial analyses were combined with data from an on-farm observation and a questionnaire to clarify the associations between farm factors and prevalence of L. monocytogenes. The prevalence of L. monocytogenes was 11, 1, 1, 24, 5, 1, and 4% in feed and litter, rectal swabs, intestinal contents, tonsils, pluck sets (including lungs, heart, liver, and kidney), carcasses, and meat cuts, respectively. The prevalence was significantly higher in organic than in conventional pig production at the farm and slaughterhouse level, but not in meat cuts. Similar L. monocytogenes genotypes were recovered in different steps of the production chain in pigs originating from the same farm. Specific farm management factors, i.e., large group size, contact with pet and pest animals, manure treatment, use of coarse feed, access to outdoor area, hygiene practices, and drinking from the trough, influenced the presence of L. monocytogenes in pigs. L. monocytogenes was present in the production chain, and transmission of the pathogen was possible throughout the chain, from the farm to pork. Good farm-level practices can therefore be utilized to reduce the prevalence of this pathogen.

Contamination of Carcasses with Human PathogenicYersinia enterocolitica4/O:3 Originates from Pigs Infected on Farms

Pigs are considered as a major reservoir of human pathogenic Yersinia enterocolitica and a source of human yersiniosis. However, the transmission route of Y. enterocolitica from farm to pork is still unclear. The transmission of pathogenic Y. enterocolitica from pigs to carcasses and pluck sets was investigated by collecting samples from 364 individual ear-tagged pigs on the farm and at the slaughterhouse. In addition, isolated strains were analyzed, using pulsed-field gel electrophoresis. Isolation of similar genotypes of pathogenic Y. enterocolitica 4/O:3 in animals on the farm and at the slaughterhouse and in carcasses shows that carcass contamination originates from the strains a pig carries during the fattening period. Direct contamination from the carrier pig to its subsequent pluck set is also the primary contamination route for pluck sets, but cross-contamination appears to have a larger impact on pluck set contamination than on carcasses. In this study, the within-farm prevalence of pathogenic Y. enterocolitica varied from 0% to 100%, indicating specific farm factors affect the prevalence of Y. enterocolitica in pigs. The association of farm factors with the high prevalence of pathogenic Y. enterocolitica on farms was studied for the first time, using correlation and two-level logistic regression analyses. Specific farm factors, i.e. drinking from a nipple, absence of coarse feed or bedding for slaughter pigs, and no access of pest animals to pig house, were associated with a high prevalence of pathogenic Y. enterocolitica 4/O:3.

Transmission of Yersinia pseudotuberculosis in the Pork Production Chain from Farm to Slaughterhouse

The transmission of Yersinia pseudotuberculosis in the pork production chain was followed from farm to slaughterhouse by studying the same 364 pigs from different production systems at farm and slaughterhouse levels. In all, 1,785 samples were collected, and the isolated Y. pseudotuberculosis strains were analyzed by pulsed-field gel electrophoresis. The results of microbial sampling were combined with data from an on-farm observation and questionnaire study to elucidate the associations between farm factors and the prevalence of Y. pseudotuberculosis. Following the same pigs in the production chain from farm to slaughterhouse, we were able to show similar Y. pseudotuberculosis genotypes in live animals, pluck sets (containing tongue, tonsils, esophagus, trachea, heart, lungs, diaphragm, liver, and kidneys), and carcasses and to conclude that Y. pseudotuberculosis contamination originates from the farms, is transported to slaughterhouses with pigs, and transfers to pluck sets and carcasses in the slaughter process. The study also showed that the high prevalence of Y. pseudotuberculosis in live pigs predisposes carcasses and pluck sets to contamination. When production types and capacities were compared, the prevalence of Y. pseudotuberculosis was higher in organic production than in conventional production and on conventional farms with high rather than low production capacity. We were also able to associate specific farm factors with the prevalence of Y. pseudotuberculosis by using a questionnaire and on-farm observations. On farms, contact with pest animals and the outside environment and a rise in the number of pigs on the farm appear to increase the prevalence of Y. pseudotuberculosis.

Prevalence and Genetic Diversity of Listeria monocytogenes in the Tonsils of Pigs

This study was set up to establish the prevalence of Listeria monocytogenes in the tonsils of sows and fattening pigs from five Finnish slaughterhouses and to evaluate the genetic similarity of L. monocytogenes strains isolated from the tonsils. A total of 271 pig tonsils (132 tonsils from fattening pigs and 139 from sows) from five different slaughterhouses in various parts of Finland were studied from June 1999 to March 2000. Overall, 14 and 4% of pig tonsils harbored L. monocytogenes and Listeria innocua, respectively. The prevalence of L. monocytogenes in tonsils of fattening pigs (22%) was significantly higher than in sows (6%). The isolates (n = 38) recovered from tonsils showed a wide genetic diversity by means of 24 different pulsed- eld gel electrophoresis (PFGE) types presented by the strains. Moreover, in numerical analyses of restriction patterns, no association was found between the clustering of strains and the slaughterhouses, and strains showing a similar PFGE type were recovered from pigs of different slaughterhouses. The high prevalence of L. monocytogenes showing various PFGE types in the tonsils of pigs could indicate a potential source of contamination of pluck sets, carcasses, and the slaughterhouse environment and of subsequent processing steps.

Molecular epidemiology of Yersinia enterocolitica 4/O:3.

ConclusionsThe main source of sporadic human YE 4:O3 infections in Finland is the pig. YE 4:O3 is a common bacterium in slaughtered pigs, especially in tonsils. During evisceration, the tonsils are removed in conjunction with the pluck set (tongue, oesophagus, trachea, heart, lungs, diaphragm, liver and kidneys). The spread of YE 4:O3 from highly contaminated tonsils to the offal can not be avoided, especially when they hang together on a hook. Contaminated pig tongues, hearts, livers and kidneys have shown to be an important transmission vehicle of this bacterium from pigs to man. The only way to prevent the spread of pathogenic YE from pig tonsils to offal, carcasses and the environment is to modify the European Union legislation (64/433/EEC), to mandate that the head, containing the tonsils and tongue, should be removed prior to evisceration and that inspection and handling of the head, tonsils and tongue should occur in a separate room.

High Prevalence of Yersinia enterocolitica 4:O3 on Pig Offal in Southern Germany: A Slaughtering Technique Problem

Prevalence and contamination routes of pathogenic Yersinia enterocolitica were studied in Southern Germany. Tonsil and faeces samples of 50 fattening pigs, 140 offal samples and 120 minced meat samples were examined. Pig and offal samples were collected from a slaughterhouse approved by the European Union, and minced meat samples from two large meat factories. Yersinia enterocolitica was isolated using direct plating, overnight enrichment and selective enrichment in MRB and ITC broth. The isolates were bio- and serotyped, and pathogenicity was studied using two plasmid-encoded virulence markers: calcium dependence and Congo red absorption. The genotypes were studied with pulsed-field gel electrophoresis using NotI enzyme. Prevalence of pathogenic Y. enterocolitica 4:O3 was 60% and 10% in tonsils and faeces of fattening pigs, respectively. Besides tonsils, prevalence of pathogenic Y. enterocolitica 4:O3 was also high in other pluck set samples, including tongues, lungs, hearts, diaphragms and livers. However, the highest isolation rate was obtained from the tonsils. Kidneys, which were not attached to the pluck set and did not hang together with tonsils on the rack, had the lowest isolation rate. Yersinia enterocolitica 4:O3 was isolated from 12% of minced meat samples. A total of 25 NotI profiles were obtained from porcine samples. The most common genotype, NBI, found in tonsils was also the most common type recovered from offal and minced meat samples. The high contamination rate of tonsils, and the indistinguishable NotI profiles obtained from tonsils and offal indicate that the tonsils contaminate offal when they are removed and hung on the rack together. When the head, with the tonsils and tongue, is not removed prior to evisceration and is not handled and inspected separately, it is difficult to control the spread of Y. enterocolitica 4:O3 from tonsils to the carcass, and subsequently, to meat.

Listeria monocytogenes Contamination Pattern in Pig Slaughterhouses

Ten low-capacity slaughterhouses were examined for Listeria by collecting a total of 373 samples, of which 50, 250, and 73 were taken from carcasses, pluck sets, and the slaughterhouse environment, respectively. Six slaughterhouses and 9% of all samples were positive for Listeria monocytogenes. Of the samples taken from pluck sets, 9% were positive for L. monocytogenes, the highest prevalence occurring in tongue and tonsil samples, at 14% and 12%, respectively. Six of 50 (12%) carcasses were contaminated with L. monocytogenes. In the slaughterhouse environment, L. monocytogenes was detected in two, one, one, and one sample originating from the saws, drain, door, and table, respectively. Carcasses were contaminated with L. monocytogenes in those two slaughterhouses, where the mechanical saws, used for both brisket and back splitting, were also positive for L. monocytogenes. A total of 58 L. monocytogenes isolates were characterized by pulsed-field gel electrophoresis typing. The isolates were divided into 18 pulsotypes, 15 of which were detected in pluck sets. In two slaughterhouses, where the carcasses were contaminated with L. monocytogenes, the same pulsotypes were also recovered from splitting saws. In addition, identical pulsotypes were recovered from pluck sets. Our findings indicate that L. monocytogenes of tongue and tonsil origin may contaminate the slaughtering equipment that may in turn spread the pathogen to carcasses. Thus, it is of the utmost importance to follow good manufacturing practices and to have efficient cleaning and disinfection procedures to prevent equipment being contaminated with L. monocytogenes.

Contamination of Carcasses, Offals, and the Environment with yadA-Positive Yersinia enterocolitica in a Pig Slaughterhouse

This study was carried out in order to evaluate the contamination of the pig-slaughtering line with pathogenic Yersinia enterocolitica carrying the yadA gene. A total of 292 samples were collected from the slaughterhouse; 131 swab samples from pig carcasses, ears, livers, kidneys, and hearts; 89 swab samples from the environment; and 72 sedimentation samples from the air. All surface samples were studied with both the polymerase chain reaction (PCR) and culture methods. The contamination rate of edible pig offals was high with both methods. Using PCR, the detection rates of yadA-positive Y. enterocolitica for livers, kidneys, and hearts were 38, 86, and 63%, respectively, and using the culture method, the detection rates were 31, 69, and 50%, respectively. Pathogenic Y. enterocolitica was also detected from different environmental sites in the slaughterhouse. Using PCR, 13% of the surface samples from the environment were contaminated with yadA-positive Y. enterocolitica. PCR-positive samples were found on the brisket saw, the hook from which the pluck set (heart, lungs, esophagus, trachea, diaphragm, liver, kidneys, and tongue with tonsils) hang, the knife used for evisceration, the floors in the eviscerating area and the weighing area, the meat-cutting table, the aprons used by trimming workers, the computer used in the meat-inspection area, and the coffeemaker used by slaughterhouse workers. The respective detection rate (6%) was considerably lower when we used the culture method. Pathogenic Y. enterocolitica was isolated from the air in the bleeding area. Bioserotype 4/O:3 was the only pathogenic bioserotype isolated in this study. A total of 113 isolates of type 4/O:3 were characterized with pulsed-field gel electrophoresis using NotI and XbaI digests. By combining these profiles, nine different pulsotypes were obtained, the most common of which (1a) was found in 19 (61%) of 31 samples from different sites. This is the same type that has dominated in pig tonsils, which suggests that tonsils may be the source of Y. enterocolitica contamination in the slaughterhouse. The four pulsotypes (1a, 4g, 6g, and 19q) found on edible offals were the same as those found in tonsils, which supports our hypothesis that tonsils are the contamination source for the liver, heart, and kidneys.