Escherichia coli O157 and non-O157 Shiga toxin-producing Escherichia coli in fecal samples of finished pigs at slaughter in Switzerland

Fecal samples from 630 slaughtered finisher pigs were examined by PCR to assess the shedding of Escherichia coli O157 (rfbE) and Shiga toxin-producing E. coli (STEC, stx). The proportion of positive samples was 7.5% for rfbE and 22% for stx. By colony hybridization, 31 E. coli O157 and 45 STEC strains were isolated, and these strains were further characterized by phenotypic and genotypic traits. Among E. coli O157 strains, 30 were sorbitol positive, 30 had an H type other than H7, and none harbored stx genes. Intimin (eae), enterohemolysin (ehxA), EAST1 (astA), and porcine A/E-associated protein (paa) were present in 10, 3, 26, and 6% of strains. Among them, one eae-gamma1-positive O157:H7 strain testing positive for ehxA and astA and two eae-alpha1-positive O157:H45 strains were classified as enteropathogenic E. coli (EPEC). The O157:H45 EPEC harbored the EAF plasmid and the bfpA gene, factors characteristic for typical EPEC. The isolated STEC strains (43 sorbitol positive) belonged to 11 O:H serotypes, including three previously reported in human STEC causing hemolytic uremic syndrome (O9:H-, O26:H-, and O103:H2). All but one strain harbored stx2e. The eae and ehxA genes, which are strongly correlated with human disease, were present in only one O103:H2 strain positive for stx1 and paa, whereas the astA gene was found more frequently (14 strains). High prevalence of STEC was found among finisher pigs, but according to the virulence factors the majority of these strains seem to be of low virulence.     

Relationships between subjective and objective assessments of stress at slaughter and meat quality in pigs

A study was carried out to relate subjective and objective measures of stress at slaughter and meat quality in pigs. Thirteen slaughter plants were visited. The systems used for handling the pigs pre-slaughter and the levels of stress experienced by the animals were subjectively assessed. The sound level immediately before stunning was also measured. Generally, systems that were rated as being most stressful also produced higher levels of sound, probably because of the vocalisations of the pigs. As the size of plant increased, there was a tendency for the level of stress, and the recorded sound level, to increase. This appeared to be because larger plants operated faster and were more likely to use restraining conveyors supplied by races to handle the animals before stunning. The restraint associated with these seems stressful to pigs. Five plants were selected for further study. Two had been assessed as having handling systems that produced a low level of stress in the pigs, one as having a system producing a medium level, and two as having poor systems producing high levels of stress. Blood samples were collected at exsanguination, and meat quality was assessed. As the level of subjectively assessed stress experienced by the pigs increased, so did the average blood levels of lactate and creatine phosphokinase (CPK). There was also a progressive increase in the potential incidence of pale, soft, exudative (PSE) and dark, firm, dry (DFD) meat in the plants using more stressful handling systems. Additionally, there were positive relationships between sound level and lactate and CPK, and sound level and indices of poorer meat quality. Cortisol concentrations were not different in pigs killed in the different systems and probably reflect events earlier in the handling process, such as in transport and lairage, rather than the stress experienced immediately before stunning. The overall conclusion was that subjective assessments of the stress suffered by pigs correlate well with objective measures and that higher stress levels are associated with poorer meat quality.     

Content of polyamines in by-products of slaughter pigs

The concentrations of putrescine, spermidine and spermine were assessed in various by-products of slaughtered pigs (Pietrain × Landrace breed, with a carcass weight of 90–105 kg). A total of 210 samples of muscular tissues (heart, tongue, diaphragm and esophagus) and inner organs (liver, kidney, spleen, lung, salivary gland and pancreas) were tested. Polyamine concentrations in non-skeletal muscles of pigs were similar to the polyamine concentrations reported for skeletal muscle. Inner organs, however, were characterized by approximately three times higher polyamine concentrations. These data can be useful to assess the alimentary polyamine exposure of humans or pets. The median spermidine: spermine ratio (weight base) was >0.1, and, thus, higher than that observed in skeletal muscles.     

Muscle glycogen depletion pattern in halothane-gene-free pigs at slaughter and its relation to meat quality

Muscle fibre type composition and glycogen depletion pattern at slaughter as related to meat quality, were studied in M. longissimus dorsi of halothane-gene-free Swedish Yorkshire pigs fed a high (n=19; 10 entire males and 9 gilts) or a low (n=18; 10 entire males and 8 gilts) protein diet. The muscle consisted of, on average, 8% type I, 9% type IIA and 83% type IIB fibres. Muscle fibre areas were significantly smaller in entire male pigs than in gilts irrespective of fibre type. There were no marked differences in muscle characteristics between pigs fed the low and high protein diets. Low glycogen concentrations were found in most type I and type IIA muscle fibres, while a greater variation in glycogen content was evident in type IIB fibres. The pigs were divided into two groups according to the proportion of glycogen depleted IIB fibres (more or less than 30% depleted IIB fibres). In the group where 30% or more of the type IIB fibres were glycogen depleted, a tendency toward DFD meat (dry, firm, dark) was seen, as the meat had higher ultimate pH (5·62 vs 5·52; p=0·02), lower drip loss (2·7% vs 4·4%; p=0·007) and lower reflectance value (darker meat; 16·5 vs 20·6 EEL units; p=0·0005), compared with the group with less than 30% depleted IIB fibres. No difference in total glycogen content was found between these two groups. This indicates that the distribution of glycogen in different fibre types seems to be of importance for the ultimate meat quality.     

Prevalence of pigs infected by Salmonella Typhimurium at slaughter after an enterocolitis outbreak

A cross-sectional study was performed to estimate the prevalence of slaughter pigs infected by Salmonella typhimurium after an enterocolitis outbreak in a commercial pig farm, which was characterised by diarrhoea during the growing phase. Anatomopathological and histopathological findings were suggestive of salmonellosis, which was further confirmed by isolation of S. typhimurium from organs and faeces samples from diseased animals. Ileocolic lymph nodes were aseptically collected from 43 pigs during slaughter procedures. The estimated prevalence of Salmonella-infected pigs was 53.48% [confidence interval (CI): 42.94:64.02%]. This finding demonstrates that the carriage of S. typhimurium at slaughter might be high if pigs originate from a batch previously affected by Salmonella-enterocolitis outbreak at the pre-harvest pork production chain.     

Toxic and essential metals in liver, kidney and muscle of pigs at slaughter in Galicia, north-west Spain

The aims of the study were to evaluate toxic and essential metal concentrations in meat and offal from pigs in north-west Spain to compare these with reported metal concentrations in pigs in other countries and in cattle in this region, and to relate the observed concentrations to maximum acceptable concentrations. Samples from 63 pigs aged 6 months were randomly collected at slaughter. After acid digestion, levels of metals were determined by ICP-OES and ICP-MS. As regards the toxic metals, mean concentrations in liver, kidney and muscle were 0.073, 0.308 and 0.009 mg kg^-1 fresh weight for cadmium, 0.004, 0.008 and 0.003 mg kg^-1 for lead, 0.013, 0.011 and 0.003 mg kg^-1 for arsenic, and 0.001, 0.002 and 0.001 mg kg^-1 for mercury. These concentrations can be considered low, and in general similar to those reported in similar studies in recent years. In addition, maximum admissible concentrations established by the European Union were not exceeded in any sample. As regards the essential metals, concentrations in liver, kidney and muscle were 14.9, 5.63 and 6.85 mg kg^-1 for copper, 81.3, 28.9 and 42.5 mg kg^-1 for zinc, 195, 51.6 and 26.5 mg kg^-1 for iron; 1.17, 2.51 and 0.656 mg kg^-1 for selenium, 3.32, 1.56 and 1.01 mg kg^-1 for manganese, 0.023, 0.027 and 0.003 mg kg^-1 for cobalt, 0.120, 0.077 and 0.131 mg kg^-1 for chromium, 0.009, 0.027 and 0.026 mg kg^-1 for nickel, and 1.62, 0.683 and 0.140 mg kg^-1 for molybdenum. These concentrations are all within the accepted adequate-safe ranges for this animal species, and in general are in line with those previously reported in the literature.     

Compensatory growth in slaughter pigs reared under organic conditions

BACKGROUND: Compensatory growth is the physiological process leading to accelerated growth following a period of growth retardation. This study assessed different feeding strategies that may induce compensatory growth. Pigs from two sire breeds, reared under organic conditions, were subjected to: (1) ad libitum feeding; (2) 0.7× ad libitum feeding; (3) 0.7× ad libitum feeding for 25 days followed by ad libitum feeding to slaughter; and (4) as (3) but finished with an energy‐ and vitamin E‐enriched diet. RESULTS: Compared to the performance of ad libitum fed pigs, re‐alimentation was not capable of fully compensating the effect of the imposed feed restriction either in the number of days used to reach the same slaughter weight (+4% to 7%) or in the slaughter weight achieved in the same number of feeding days (?0.5% to 2.0%, P = 0.65 and 0.11). CONCLUSION: It is reasonable to propose that although compensatory growth does occur by re‐alimentation after feed restriction, the compensation is far from always complete. The latter is a crucial aspect that has to be taken into account when considering the application of feeding strategies expected to lead to compensatory growth in organic pig production. The expectation of compensatory growth alone does not necessarily justify the application of these strategies. Copyright © 2009 Society of Chemical Industry     

Salmonella in slaughter pigs: the effect of logistic slaughter procedures of pigs on the prevalence of Salmonella in pork

A substantial part of the finishing pigs in the Netherlands is infected with Salmonella. Infection of pigs with Salmonella can occur already on the farm. Pigs can also get infected or contaminated during transport, lairage or slaughter. The aim of this study was to evaluate the effect of separating pigs from Salmonella-infected farms from pigs from Salmonella-free farms during transport, lairage and slaughter on the prevalence of Salmonella on pork after slaughter. Two experiments were carried out. In the first experiment, farms were selected to participate, based on serology of the pigs (Dutch Salmonella ELISA). The pigs were slaughtered at the beginning of the day: firstly, sero-negative herds, secondly, sero-positive herds and thirdly, again sero-negative herds. The latter were slaughtered to investigate the effect of a contaminated slaughterline due to a previously slaughtered positive herd. In the second experiment, farms were selected to participate, based on both serology and bacteriology of the pigs on the farm. Two hundred pigs from Salmonella-free farms were slaughtered after 200 pigs from Salmonella-infected farms. Results showed that the prevalence of Salmonella in pork samples of sero-negative herds was lower than in samples of sero-positive herds. Results also showed that Salmonella contamination of carcasses after slaughter was partially caused by Salmonella-infected herds that were slaughtered before, and partially by residential flora of the slaughterhouse. It is concluded that separate slaughter of sero-negative pig herds can be useful to decrease the prevalence of Salmonella-contaminated pork after slaughter. To avoid cross-contamination by residential flora from trucks, lairage and slaughterline, cleaning and disinfection have to be improved.     

Detection of Salmonella spp., Yersinia enterocolitica and verocytotoxin-producing Escherichia coli O157 in pigs at slaughter in Italy

From December 1999 to December 2000, 150 pigs were randomly selected in two large abattoirs of northern Italy. Caecal material and carcass swabs were collected and examined for Salmonella, Yersinia enterocolitica, and Escherichia coli O157. Tonsils were examined for Salmonella and Y. enterocolitica. Salmonella was isolated from the intestinal content of 55 (36.7%) specimens, from 8 (5.3%) tonsils, and from 9 (6.0%) carcasses. Ten different serotypes were detected; the more common were Salmonella derby (37.8%), Salmonella bredeney (21.6%), and Salmonella typhimurium (14.8%). S. typhimurium isolates that belonged to phage-types DT104 and DT208 were 45% and 27.3%, respectively; 18.2% belonged to U302 and 9.1% were non-typeable. Y. enterocolitica was detected in the intestinal matter of 6 (4.0%) slaughtered pigs and in 22 (14.7%) tonsils; however, this pathogen was not found on carcasses. The majority of Y. enterocolitica isolates (82.1%) belonged to serotype O:3 biotype 4, one (3.6%) belonged to serotype O:9, and 13% did not belong to any known biotype. Verocytotoxin-producing E. coli (VTEC) O157 was isolated from the intestinal content of one (0.7%) slaughtered pig and from one (0.7%) carcass; four (2.7%) faecal samples contained E. coli O157 strains negative for the presence of both eae and VT genes.     

Salmonella in slaughter pigs: prevalence, serotypes and critical control points during slaughter in two slaughterhouses

The purpose of this study was to show the distribution of Salmonella in slaughtered pigs and the environment of the slaughterhouse. 1114 samples of slaughtered pigs (six different samples for Salmonella isolation and one serum sample for ELISA on antibodies per pig) and 477 samples of the slaughterhouse environment were collected in two slaughterhouses on two sampling days per slaughterhouse. Salmonella was isolated from one or more samples of 47% of the pigs. The highest prevalence of Salmonella was observed in rectal content samples (25.6%), whereas the lowest prevalence of Salmonella was observed on the carcasses (1.4%). The prevalence of Salmonella in other samples was: 19.6% in tonsils, 9.3% on livers, 9.3% on tongues, and 9.3% in mesenterial lymphnodes. The prevalence of Salmonella in environmental samples was high in the drain water samples in both slaughterhouses (61%) and on the carcass splitter in one slaughterhouse (33%). Salmonella typhimurium was the most frequently isolated serotype in pig samples and environmental samples in both slaughterhouses: 43% of the Salmonella isolates from pigs and 33% of the Salmonella isolates from the environment was S. typhimurium.

The results of this study show that Salmonella prevalences in pigs differ a lot, depending on which part of the pig is sampled. Not all different samples of the pig will become available for human consumption, but collecting more than one sample per pig showed that Salmonella can be found in almost the whole pig. The result of surface samples of carcass and liver gives information about hygiene during the slaughter process; the result of tonsils, lymphnodes and rectal contents, combined with the serological result, gives information about infection of the pig before the slaughter process (on the farm, during transport or in lairage).

It can be concluded that results of Salmonella isolation of slaughter pigs should always be carefully interpreted, depending on the type of sample that has been collected.     

Associations between on-farm and slaughter plant detection of Salmonella in market-weight pigs

Thirty swine production units in the midwestern United States were studied to assess the relationship of herd-level prevalence of Salmonella on the farm prior to slaughter versus at slaughter. Fecal samples were collected from 30 pigs on each farm within 48 h of slaughter, and 30 ileocecal lymph node samples were collected in the same shipment cohort at slaughter. Samples were cultured by conventional methods, and Salmonella identity was confirmed by serotyping. Overall, 11.7% (n = 105) of the fecal samples and 14.9% (n = 133) of the ileocecal lymph node samples were positive for Salmonella. Seventeen of the farms (56.7%) had one or more positive fecal samples, and 24 (80.0%) had one or more positive ileocecal lymph node samples. Twenty-four recognized serotypes and three additional distinct antigenic types were identified. Among all isolates, 56.5% had serotypes that were duplicated both on the farm and at slaughter for a particular cohort, whereas the remaining samples lacked a duplicate serotype in the other sample type. There was a positive correlation in the prevalence of Salmonella between fecal samples and ileocecal lymph node samples (Spearman's p = 0.75; 95% confidence interval [CI], 0.62 to 0.89). Linear regression analysis was used to identify two farms that biased the regression estimates. Excluding these farms, 62% of the variance in farm slaughter Salmonella prevalence was accounted for by on-farm prevalence. The analyses suggest that the prevalence of Salmonella spp. at slaughter can be predicted from preslaughter on-farm sampling and vice versa.     

Isolation and molecular characterization of Escherichia coli O157 isolated from cattle,pigs and chickens at slaughter

From 1999 until 2001, 3625 food samples were examined for the presence of Escherichia coli O157. Samples were from bovine origin (ground beef, n=549; carcasses, n=2452), calves (carcasses, n=147), chicken (breast, n=203; carcasses, n=71) and pigs (carcasses, n=85; trimmings, n=118). Vidas ECO detected 451 (12%) samples positive, but from only 27 (0.74%) samples was E. coli O157 isolated. One strain was isolated from bovine ground beef (0.18%), one from a pig carcass (1.17%) and all others were isolated from bovine carcasses (1.02%). All strains possessed the attaching-and-effacing gene, the enterohemorrhagic plasmid and verotoxin (VT) genes, except the strain isolated from the pig carcass that was therefore eliminated. Six of the strains were urease-positive. Strains were typed by two DNA fingerprinting methods: random amplification of polymorphic DNA (RAPD) and pulsed field gel electrophoresis (PFGE). PFGE revealed a similarity of 71.05%, while RAPD was 77.36% similar. None of the typing methods were able to classify all urease-positive strains to one pattern. Strains in the same PFGE cluster did not belong to one RAPD cluster. This paper highlights that Belgian fresh meat at retail level can be contaminated with E. coli O157 and that two different typing methods divide strains into different types.     

Muscle fibre characteristics and metabolic response at slaughter in pigs of different halothane genotypes and their relation to meat quality

Muscle samples for histochemical and biochemical analyses were taken immediately at slaughter from M. longissimus dorsi of pigs with different halothane genotypes (NN and nn). Fibre type composition was similar between groups but the nn-genotype had larger mean fibre areas and lower capillary density than the NN-genotype. At exsanguination the nn-genotype had lower muscle pH (pH(e)), higher lactate and ammonia and lower glycogen and phosphagen (ATP and CP) concentrations and twice as many glycogen-depleted type IIA and IIB fibres as compared with the NN-genotype. Muscle pH(e) was correlated positively to capillary density, glycogen and phosphagen concentrations and negatively to mean fibre area, ammonia and lactate concentrations. Ammonia concentrations were correlated negatively to ATP concentrations and positively to the percentage of glycogen-depleted IIB fibres. The highest reflectance and drip loss values were seen in the nn-genotype. The reflectance values were correlated positively to the percentage of glycogen-depleted type IIB fibres in muscle and the values for drip loss were correlated negatively to pH(e). These data show that fibre size and capillary density in muscle seem to be important factors that influence the metabolic response at slaughter and thus meat quality.     

Resting pigs on transport trailers as an intervention strategy to reduce Salmonella enterica prevalence at slaughter

Recent research has shown that much preharvest Salmonella enterica infection in pigs occurs immediately before slaughter during this rest period in the contaminated abattoir holding pens. The objective of this study was to evaluate a potential intervention strategy to reduce the prevalence of S. enterica-positive pigs at slaughter, which consisted of resting pigs prior to slaughter on their transport vehicle, instead of in the abattoir holding pen. Additionally, the effect of transportation of pigs from farm to the abattoir on S. enterica prevalence was investigated. A total of 120 animals were included in the experiment, divided in four replicates (n = 30 pigs per replicate). Fecal samples were collected from each animal at the farm and at the abattoir, where 15 randomly chosen pigs were unloaded and moved to a holding pen, while the remaining 15 pigs stayed in the transport trailer. After approximately 1.5 h of resting, both groups were slaughtered. Samples collected included distal ileum portion, cecal contents, and ileocecal lymph node. The overall S. enterica prevalence (pigs positive in at least one of the samples collected at slaughter) was higher for pigs held in the abattoir pens (40.7% versus 13.3%, P < 0.05). There was no difference (P > 0.05) for the S. enterica prevalence before and after transportation from farm to abattoir (5.8% versus 0.8%, respectively). This study demonstrates that resting pigs on the transport vehicle has the potential to decrease S. enterica levels entering the abattoir.     

Effects of age and/or weight at slaughter on longissimus dorsi muscle: Biochemical traits and sensory quality in pigs

The effect of increasing either age alone through feed restriction, or both age and weight at slaughter, on the quality of the longissimus dorsi muscle (LM) was investigated. Starting at 83 days of age and 32 kg, 80 pigs were allotted within litter to four experimental groups. All pigs were free of RYR1 mutated gene. Pigs were fed either ad libitum (A100, A130) or restricted 30% (R100, R130) and slaughtered at either 100 kg (A 100, R100) or 130 kg (A130, R130) body weight. Restricting feed intake in order to increase age at the same weight resulted in slower growth, better feed efficiency and increased leanness, whereas increasing age and weight simultaneously elicited slower growth, reduced feed efficiency and fatter carcasses. Intramuscular fat (IMF) and muscle collagen concentration were reduced by restricted feeding. Increase in both age and weight of pigs resulted in lower water, and higher protein and IMF concentrations. Although pigs were free of RYR1 gene, the PSE condition (defined as pH1 ≤ 5.9) developed in 25 carcasses, with a higher incidence in restricted pigs. PSE animals were excluded from the subsequent analysis of meat quality data. Feed restriction resulted in higher drip loss and lower a^* and c^* (saturation index) values. Longer myofibril fragments in muscle of restricted pigs on day 1 post mortem are indicative of slower maturation, while longer fragments on day 4 in heavier pigs, suggest that the extent of post mortem tenderisation could be negatively affected by the elevation of slaughter weight. Feed restriction had no significant effect on meat sensory quality, whereas increase in both age and weight resulted in lower tenderness, chewiness and mouth coating scores. Our results indicate that increasing age at a given body weight, via feed restriction, reduced IMF and collagen concentrations, and the rate of post mortem proteolysis, however, this had no significant impact on pork quality assessed after 4 days of ageing. On the other hand, increasing both age and weight at slaughter could alter pork texture, in spite of elevated IMF concentration.     

Explaining and predicting differences in meat quality through stress reactions at slaughter: The case of Large White and Duroc pigs

Large White and Duroc pigs (n=42) were group-reared on straw. Durocs were more active in the home pens and had higher basal urinary cortisol levels. During tests, Durocs touched more often an unfamiliar human, but not an unfamiliar object, than Large Whites. Pigs were experimentally (low stress) or industrially (high stress) slaughtered. Meat (Longissimus lumborum (LL), Biceps femoris (BF), Adductor femoris (AF) and Semimembranosus (SM)) was darker, more yellow, had higher ultimate pH and better water holding capacity after high, compared to low-stress slaughter. Large White meat contained less pre-slaughter glycogen, was redder and lost more drip. Slaughter conditions influenced ultimate pH of Large White more than of Duroc meat. Large Whites, and to a lesser extent Durocs, touching the human less often during the test, had faster early post-mortem LL and BF muscle metabolism. Pigs exploring the unfamiliar object more often were more aggressive during pre-slaughter mixing and had higher AF and SM ultimate pH.     

The relationship between exsanguination blood lactate concentration and carcass quality in slaughter pigs

A group of 128 cross-bred barrows were used to determine the relationship between exsanguination blood lactate concentration ([LAC]) and carcass quality following commercial marketing conditions. After 10 h of feed withdrawal, pigs were loaded on a truck with a hydraulically lifted second deck and transported approximately 1 h to the slaughter facility. Pigs were rested for 8 h and stunned with carbon dioxide. Blood lactate concentration was measured on exsanguination blood. Fourteen pork quality measurements were obtained following normal post-mortem processing. Pearson correlations were used to determine the relationships between [LAC] and the meat quality parameters. Exsanguination blood lactate concentration ranged from 4 to 19.7 mM. Higher lactate was associated with lower 60 min pH (P = 0.0004) and higher drip loss (P = 0.02). These results suggest that under low-stress loading and standard marketing conditions, exsanguination [LAC] is predictive of the rate of early post-mortem metabolism.     

Investigation of Salmonella enterica in Sardinian slaughter pigs: prevalence, serotype and genotype characterization

In order to improve the knowledge about the presence of Salmonella in pork meat in Sardinia (Italy), the prevalence and the sources of Salmonella at 5 pig slaughterhouses (slaughtered pigs and environment) were investigated and the isolates were characterised. A total of 462 samples were collected, 425 from pigs at slaughter and 41 from the slaughterhouse environment. Salmonella was isolated from 26/85 (30.5%) mesenteric lymph nodes, 14/85 (16.4%) colon contents, and from 12/85 (14.1%) carcasses and livers. Salmonella prevalence was 38% (8/21) in samples from surfaces not in contact with meat, and 35% (7/20) in those from surfaces in contact with meat. Thirty-one pigs were identified as carriers of Salmonella in lymph nodes and/or colon content, but of these, only 8 carcasses were positive. A total of 103 Salmonella isolates were serotyped and genotyped. Eight different serotypes were detected; the most common were S. Derby (44/103, 42.7%) and S. Typhimurium (24/103, 23.3%). The most prevalent S. Typhimurium phage type was DT193. Thirty-two isolates were found to be resistant to more than one antimicrobial (MDR). Pulse-field gel electrophoresis (PFGE) permitted the resolution of XbaI macrorestriction fragments of the Salmonella strains into 20 distinct pulsotypes. Combined application of a plasmid profiling assay (PPA) and PFGE gave useful additional information to assist in tracing the routes of Salmonella contamination in abattoirs. To reduce Salmonella prevalence some preventive measures should be encouraged: the origin of infected slaughter animals should be identified and direct and cross-contamination of carcasses should be avoided by adhering to HACCP principles in association with good hygiene procedures (GHP).     

Yersinia enterocolitica and Yersinia enterocolitica-like bacteria in Norwegian slaughter pigs

Yersinia spp. were isolated from the tonsils of 200 (43.4%) of 461 freshly slaughtered pigs. Y. enterocolitica comprised 92.7% of the total number of isolates, while Y. kristensenii, Y. intermedia, and Y. pseudotuberculosis comprised 6.3%, 0.5% and 0.5% respectively. Fifteen different serotypes were recognized. Serotype O:3 comprised 70.9% of the total number, followed by O:5 (6.8%), and O:6,30 (6.3%). Y. enterocolitica O:3/biotype 4, the predominating human pathogen in Europe, was isolated from 31.7% of the pigs examined. 67 (45.9%) of these isolates were potentially virulent as judged by the autoagglutination virulence assay. Three-week cold enrichment in a low-selectivity medium was the most efficient single method for recovery of Y. enterocolitica serotype O:3/biotype 4, Y. enterocolitica biotype 1, and Y. kristensenii. However, optimal recovery was achieved using a multi-method isolation technique, including a two-step procedure based on pre-enrichment followed by selective enrichment in a modified Rappaport broth.     

Isolation and characterization of verocytotoxin-producing Escherichia coli O157 from slaughter pigs and poultry

Rectal contents and tonsils from Dutch slaughter pigs collected immediately after slaughter were examined for the presence of verocytotoxin (VT)-producing Escherichia coli (VTEC) of serogroup O157 (O157 VTEC). In addition, fresh fecal material from poultry layer flocks and turkey flocks collected on poultry farms was examined for the presence of O157 VTEC. E. coli O157 strains were isolated from two (1.4%) of 145 pigs. The strains were isolated from samples of rectal contents, all samples of tonsils being negative. While all 501 fecal samples from chicken flocks were found negative, E. coli O157 strains were isolated from six (1.3%) of 459 pooled fecal samples from turkey flocks. One of the porcine isolates and one of the turkey isolates contained the VT2 gene, the E. coli attaching-and-effacing gene, as well as the enterohemorrhagic E. coli hemolysin gene. Production of VT was confirmed by cytotoxicity tests on Vero cells. Based on these characteristics, the two stains were regarded as potentially pathogenic for humans. The porcine and the turkey isolate were further characterized as being of phage types 4 and 14, respectively. While biochemically typical of E. coli O157, the remaining six isolates were nonverocytotoxigenic and negative for both the E. coli attaching-and-effacing gene and the enterohemorrhagic E. coli hemolysin gene. All eight E. coli O157 isolates did not carry genes that encode E. coli heat-labile and heat-stable enterotoxins. It was concluded that pigs and poultry can be a source of O157 VTEC strains characteristic of those causing illness in man. The extent to which pigs and poultry play a role in the epidemiology of human O157 VTEC infection needs further research.