A comparison of two evisceration methods on hygienic quality in the pelvic area of sheep carcasses.

The aim was to compare the effects of two evisceration methods under operational conditions, on the pelvic hygiene of sheep carcasses. Method 1: rectum sealed with plastic bag and pushed through the pelvic cavity. Method 2: rectum cut, placed back inside and pulled out from the carcass. The 18 largest Norwegian sheep abattoirs participated. Sampling areas were i) 400cm2 inside the pelvic cavity (n=623), ii) 100cm2 outside the circum-anal incision (n=622). There were pooled samples by swabbing the same area of five carcasses, representing totally 3115 carcasses. Mean E. coli results from Method 1: -1.61logCFU/cm2 inside and -0.25logCFU/cm2 for the outside area. Results from Method 2: -1.56logCFU/cm2 inside and -0.42logCFU/cm2 outside. There were no significant differences between the two methods. Both evisceration methods can produce carcasses that are of practically identical high hygienic quality.

Enumeration of Escherichia coli in swab samples from pre- and post-chilled pork and lamb carcasses using 3M™ Petrifilm™ Select E. coli and Simplate® Coliforms/E. coli.

The aim of the study was to compare two analytical methods; 3M Petrifilm™ Select E. coli and SimPlate® Coliforms &E. coli, for detection and enumeration of E. coli using swab samples from naturally contaminated pork and lamb carcasses that were collected before and after chilling. Blast chilling was used for pork carcasses. Swab samples (n=180) were collected from 60 warm and 60 chilled pork carcasses, and 30 warm and 30 chilled lamb carcasses, and analysed in parallel. The concordance correlation coefficient between Petrifilm and SimPlate was 0.89 for pork and 0.81 for lamb carcasses. However, the correlation was higher for warm carcasses (0.90) than chilled carcasses (0.72). For chilled lamb carcasses, the correlation was only 0.50, and SimPlate gave slightly higher results than Petrifilm (P=0.09). Slower chilling gave slightly lesser agreement between methods than for blast chilling, however, both Petrifilm and SimPlate methodologies are suitable and recommended for use in small laboratories in abattoirs.

The significance of clean and dirty animals for bacterial dynamics along the beef chain.

This study investigated the bacterial dynamics along the beef chain for clean and dirty cattle in the slaughter and processing lines, using classic quantitative methods and molecular analyses. In addition, the Norwegian national guidelines for Good Hygiene Practices in Norway were evaluated. In these guidelines, cattle presented for slaughter are categorised according to hide cleanliness, resulting in separate processing lines for meat from very dirty animals and reduced prices to farmers. The study was conducted in two commercial abattoirs in Norway. Two groups were compared; 40 visually clean cattle and 40 visually dirty cattle presented for slaughter, with 20 from each group at each abattoir. The same animals were sampled at five sampling sites: hides, carcass surfaces after dehiding, just before chilling, after chilling, and meat trimmings. Meat trimmings were sampled in only one abattoir. Three hundred and sixty samples were collected by swabbing 100 cm(2) of the brisket area at the first four sampling sites, and sampling 200 g of meat trimmings at the fifth site. The results showed that the hides of dirty cattle had more Enterobacteriaceae and higher Aerobic Plate Counts (APC) than visually clean cattle (P<0.05), however there was no significant difference for Escherichia coli. For the other sampling sites, there were no differences between the dirty and the clean group. An effect of chilling/drying of the carcass surfaces was demonstrated by the significant reduction in the number of carcasses on which E. coli and Enterobacteriaceae were detected; from 11% and 39% before chilling to 1% and 16% after chilling, respectively. Enterobacteriaceae and E. coli were detected in only three and one of the meat trimming samples, respectively. Amplification and sequencing of the 16S rRNA gene from 643 Enterobacteriaceae colonies derived from 107 samples demonstrated that Escherichia/Shigella were dominant within this family on the hides. However, after dehiding, after grading, and after chilling, the genera Citrobacter and Enterobacter dominated. The meat trimmings were dominated by the genera Kluyvera, Hafnia, and unclassified Enterobacteriaceae. The relative proportions of Escherichia/Shigella were higher for dirty animals than for clean animals, and were higher on hides than from sampling sites further down the chain (P<0.05). The minor differences in contamination on carcass surfaces and meat trimmings between clean and dirty cattle indicate that separate processing lines in Norwegian abattoirs seem to be unnecessary.

Effects of hygienic treatments during slaughtering on microbial dynamics and contamination of sheep meat.

The aims of this study were to investigate bacterial dynamics in the sheep meat chain, from fleece to meat trimmings, using both quantitative and qualitative analyses, and to study the effects on microbial load associated with the hygienic interventions of: i) shearing sheep immediately before slaughter, ii) manual steam vacuum pasteurisation, iii) hot water pasteurisation of carcasses, followed by iv) chilling. A further aim was to provide evidence to determine whether or not unshorn sheep should be handled in a processing line separate from that of shorn sheep in Norwegian abattoirs. A total of 176 surface swab samples were collected from three sites along the value chain: i) on fleeces, ii) on carcasses at the end of the slaughter line, and iii) on carcasses after chilling for 24h, and 32 samples were collected from meat trimmings. The results showed that Aerobic Plate Counts (APC) were lower for the shorn group compared to the unshorn group, both on carcasses before chilling and after chilling (difference of 0.8 and 0.9logCFU/1000cm(2) (p≤0.05), respectively) and in meat trimmings (difference of 0.5logCFU/g (p≤0.05)). Hygienic treatments were used on carcasses derived from unshorn sheep, and steam vacuum treatment reduced Escherichia coli, Enterobacteriaceae, and APC before chilling by 1.2, 1.0, and 0.6logCFU/1000cm(2) (p≤0.05), respectively, and hot water pasteurisation, in addition to chilling, reduced E. coli, Enterobacteriaceae, and APC by 0.7, 1.0, and 0.9logCFU/1000cm(2) (p≤0.05), respectively, compared with untreated carcasses. The effect of chilling was shown by the significant reduction of number of carcasses where E. coli were detected; from 65% (13/20) of the shorn group before chilling to 35% (7/20) after chilling, and from 90% (36/40) to 45% (9/20) of the unshorn group. Sequencing of the 16S rRNA gene derived from 316 colonies of Enterobacteriaceae showed a tendency for the relative proportion of the genus Escherichia/Shigella, compared with other genera within Enterobacteriaceae, to be greater for unshorn, untreated sheep than from the other groups at the sampling locations along the meat chain. The study showed that steam vacuum and hot water pasteurisation reduced the contamination of carcasses derived from unshorn sheep, down to the level of the shorn group, and thus can replace the separate processing line for unshorn sheep. Indeed, the low microbial contamination in meat trimmings for all groups indicates that the separate processing line is unnecessary.

Effects of shearing and fleece cleanliness on microbiological contamination of lamb carcasses.

The meat industry in Norway has developed national guidelines for Good Hygiene Practices for slaughtering and skinning, based on categorisation of animals. These include shearing sheep and lambs in the abattoirs immediately before slaughter. The aim of this study was to investigate microbiological carcass contamination associated with: (i) different shearing regimes; (ii) fleece cleanliness; and (iii) the slaughter process. In addition, the efficacy of the national guidelines in reducing microbial contamination was evaluated. A total of 280 swab samples were collected from the brisket areas (100 cm(2)) of 140 naturally contaminated lamb carcasses in a commercial abattoir. Half the samples were collected at skinning of brisket areas at the start of the slaughter-line and half of them were collected at the end of slaughter-line, just before chilling. The lambs were divided into four groups (n=35) according to the duration of the period between shearing and slaughter: (i) 0 days (shorn at the abattoir immediately before slaughter); (ii) three days; (iii) seven days; and (iv) not shorn. Mean log colony forming units (CFU) per 100 cm(2) at skinning were 5.78 and 6.95 for aerobic plate count (APC) (P<0.05), 1.65 and 2.78 for Escherichia coli (P<0.05) for shorn and unshorn lambs, respectively. For shorn lambs, divided according to the period between shearing and slaughter, the mean log CFU per 100 cm(2) were 5.45, 5.75, 6.12 (APC) and 1.77, 1.46, 1.71 (E. coli) for the 0-days, 3-days and 7-days groups, respectively (P<0.05 for the difference between 0- and 7-days groups in APC results). A four-category scale (0-3) was used for assessing fleece cleanliness before skinning. Visually clean lambs (score '0') had lower levels of APC on the carcass surfaces than those categorised as dirty (score '2-3') (P<0.05). The carcasses at the end of the slaughter-line had lower levels of APC than they had at skinning. However, the statistical significant reduction of E. coli on carcass surfaces at skinning point for shorn lambs, were impaired and no longer significantly different from the unshorn group at the end of the slaughter-line. The increased E. coli level at the end of the slaughter-line might be explained by weaknesses related to slaughter hygiene in particular suboptimal evisceration in the abattoir which was used as a basis for our trial, and thus the national guidelines concerning shearing had not the fully intended effect on reducing microbial carcass contamination.

Hot water surface pasteurisation of lamb carcasses: microbial effects and cost-benefit considerations.

Although hot water pasteurisation of carcasses is accepted as a general intervention in USA, this is not the case in Europe. The aims of this study were (i) to evaluate the microbiological effects of hot water pasteurisation of lamb carcasses, both after slaughtering and dressing and following subsequent chilling and storage; (ii) to discuss hot water pasteurisation from a public health and cost-benefit perspective; (iii) to discuss the benefits of hot water pasteurisation compared with use of separate meat processing streams for high-risk carcasses; (iv) to evaluate the use of recycled hot water in a hygienic context and in relation to EU regulations; and (v) to consider the technological and sensory aspects of hot water pasteurisation of lamb carcasses. Samples were collected from 420 naturally contaminated lamb carcasses, with 50% of the carcasses (n=210) subject to hot water pasteurisation at 82 °C for 8s immediately after slaughter. Surface swab samples from 4500 cm² areas on carcasses were collected at slaughter, after chilling for 24 h, and after chilling for five days. The microbial analyses included Escherichia coli, Enterobacteriaceae, Bacillus cereus, Clostridium perfringens and aerobic plate count (APC). A resuscitation step using Tryptone Soya Agar was included in the microbiological analyses. Hot water pasteurisation significantly reduced the levels of E. coli, Enterobacteriaceae, B. cereus and APC (all P<0.001). E. coli colony forming unit (CFU) reduction was 99.5%, corresponding to a reduction of 1.85 log CFU per carcass. E. coli was isolated from 66% of control carcasses and from 26% of pasteurised carcasses. After 24h storage, the reduction in E. coli was increased to 2.02 log, and after five days E. coli could not be isolated from the pasteurised carcasses. These results suggest that surface pasteurisation could be an important and efficient procedure (critical control point) for reducing generic E. coli and thereby shiga toxin-producing E. coli on carcasses, and thus the risk for disease among consumers. The recycled water had acceptable physical and chemical parameters and no spore-forming bacteria were detected. Although some carcass discolouration was observed, after 24h the colour was acceptable. Our data provide relevant input for some of the data gaps regarding hot water pasteurisation and indicate that replacing the expensive system of separate processing of high-risk carcasses with hot water surface pasteurisation should be considered as a serious option.

The effect of blast chilling on occurrence of human pathogenic Yersinia enterocolitica compared to Campylobacter spp. and numbers of hygienic indicators on pig carcasses.

In this study, the occurrence of Yersinia enterocolitica on pig carcasses was compared to the occurrence of Campylobacter spp., and to the numbers of aerobic micro-organisms, coliform bacteria, thermotolerant coliform bacteria, and Escherichia coli before and after blast chilling. Y. enterocolitica O:3/biovar 4 was isolated from five (8.3%) of 60 carcasses before blast chilling, and also from five of them 1 h after blast chilling. Therefore this procedure does not seem to have a significant effect on the occurrence of pathogenic Y. enterocolitica on pig carcasses. Y. enterocolitica O:9/biovar 2 was isolated from a pig source in Norway for the first time when this sero/biovariant was isolated from one of the carcasses before blast chilling. Campylobacter spp. was isolated from 34 (56.7%) of 60 carcass samples before blast chilling. After blast chilling Campylobacter spp. was isolated from only one (1.7%) of the 60 carcasses. There was a significant decrease of the numbers of coliform bacteria, thermotolerant coliform bacteria and E. coli after blast chilling. The number of aerobic micro-organisms did not decrease after this step. In contrast to the drastic decrease in the occurrence of campylobacter-positive carcasses and the significant decrease of the numbers of coliform bacteria, thermotolerant coliform bacteria and E. coli, blast chilling does not seem to have a significant effect on the occurrence of human pathogenic Y. enterocolitica on pig carcasses.

Hot boning of intact carcasses: a procedure to avoid central nervous system self-contamination in beef and beef products.

Compared with traditional boning of split refrigerated carcasses, hot boning of intact carcasses (the removal of meat from the skeleton prerigor) provides several commercially important cuts, may improve quality and reduce refrigeration costs, and may reduce the contamination of carcasses with central nervous system (CNS) tissue. In a comparative study of hot boning of intact and split carcasses, the CNS tissue contamination of intact carcasses was negligible (as measured with the CNS-related proteins glial fibrillary acidic protein and S-100 protein), but split carcasses were highly contaminated. The same trends were observed for dissection worktables used during the boning process. Most current boning plants have processing lines that are organized for boning carcass quarters, where the carcasses, in addition to transversal division, also are split horizontally. This part of the boning process was incorporated in the design of our study. Nine of the 18 intact carcasses were split horizontally between thoracic vertebrae 10 and 11 before they were hot boned. CNS tissue contamination was not detected on the carcass site related to this procedure. The amount of CNS tissue contamination was similar in boned cuts and minced meat from split and intact carcasses, except in the forerib. Boning of split carcasses appears to reduce CNS tissue contamination significantly to a level comparable to that of intact hot-boned carcasses.

Molecular epidemiology and disinfectant susceptibility of Listeria monocytogenes from meat processing plants and human infections.

We have investigated the molecular epidemiology of Listeria monocytogenes from the meat processing industry producing cold cuts and from cases of human listeriosis by discriminative pulsed-field gel electrophoresis (PFGE). A subset of the isolates was also investigated for susceptibility to a disinfectant based on quaternary ammonium compounds (QAC) frequently used in the meat processing industry. The purpose of this investigation was to obtain knowledge of sources, routes of contamination and genetic types of L. monocytogenes present along the production line in the meat processing industry, and to compare meat industry isolates and human isolates. Of the 222 isolates from four meat-processing plants, 200 were from two plants responsible for nearly 50% of the production of cold cuts in the Norwegian market. The strain collection included historical routinely sampled isolates (1989-2002) and isolates systematically sampled through a one year period (November 2001 to November 2002) from fresh meat and production environments in three plants. No isolates were obtained in samples from employees (throat, faeces). Human strains included all available reported isolates from Norwegian patients in selected time periods. The L. monocytogenes PFGE data showed a large genetic heterogeneity, with isolates separated into two genetic lineages and further subdivided into 56 different PFGE profiles. Certain profiles were observed on both sides of production (before and after heat treatment) indicating contamination of end products by fresh meat or fresh meat environments. While fresh meat isolates almost exclusively grouped within lineage I, isolates from end products showed a more balanced distribution between lineages I and II. Ten profiles were common among isolates from human and meat industry. Typing of human isolates identified a previously unrecognised outbreak. Generally, a higher QAC resistance incidence was observed among isolates from the meat processing industry than among human isolates although large plant to plant differences were indicated. No correlation between resistance and PFGE profile or resistance and persistence was observed.

Occurrence of Yersinia enterocolitica and Campylobacter spp. in slaughter pigs and consequences for meat inspection, slaughtering, and dressing procedures.

The purpose of the present investigation was to assess the occurrence of Yersinia enterocolitica and Campylobacter spp. in the lymphoid tissues and intestinal tract in pigs and the risk for contamination during the compulsory meat inspection procedures and the procedures during slaughtering and dressing. Another objective of the investigation was to compare traditional isolation methods, the use of a polymerase chain reaction (PCR) method (BUGS'n BEADS bacterial DNA isolation kit) and an ELISA method (VIDAS CAM) as tools in risk management in the slaughterhouse. The results indicate that the compulsory procedure for the incision of the submaxillary lymph nodes represents a cross-contamination risk for virulent Yersinia. In the screening of 97 animals in 1999, 5.2% of the samples were positive, and by the sampling of 24 samples in 2000-2001, 12.5% of the samples were positive. In the last case, Y. enterocolitica O:3 was found in the kidney region in one of the subsequent carcasses that was only touched by the meat inspection personnel before sampling. In addition, incision of the mesenteric lymph nodes might represent a cross-contamination risk since 8.3% of the samples were positive. The association between antibody titres and the occurrence of virulent yersiniae in the tonsils (21-18) was striking, with virulent yersiniae found in the tonsils in most pigs with high titres. The contents of the stomach, ileum, caecum, and colon also represent contamination risks for Y. enterocolitica O:3 if the slaughterhouse personnel cuts into the viscera with their knives by accident; the frequency of virulent Yersinia varied from 4.2% to 16.7% within these sections. Campylobacter was detected in the gastrointestinal tract of all pigs, and the high contamination of tonsils (66.7%) and intestinal tract (100%) might represent an occupational health hazard. There was no statistical difference between the traditional method for isolation of Y. enterocolitica [International Organization for Standardization, 1994. Microbiology-General Guidance for the Detection of Presumptive Pathogenic Yersinia enterocolitica (ISO 10273). International Organization for Standardization, Genève, Switzerland (16 pp.)] and the BUGS'n BEADS detection method for virulent Y. enterocolitica. Likewise, there was no statistical difference between the traditional method for isolation of Campylobacter spp. [Nordic Committee on Food Analysis, 1990. Campylobacter jejuni/coli. Detection in Food. Method No. 119, 2nd ed. Nordic Committee on Food Analysis, Esbo (7 pp.)] and the BUGS'n BEADS detection method or the VIDAS CAM method for detection of Campylobacter spp.