Monitoring of microbial contamination of stick wound in swine carcasses

This study was done to evaluate the microbial contamination by Salmonella spp., Escherichia coli, fecal coliforms, and total aerobic count of the stick wound of swine carcasses. The effectiveness of trimming the stick wound in the 2 Québec slaughterhouses visited was evaluated. A bacteriological analysis was done on 276 stick wounds. Results indicated that, before trimming, 0.9% stick wounds were contaminated by Salmonella spp. Contamination by coliforms was observed in 40.6% of samples, and 27.7% were positive for E. coli. After trimming the stick wounds, 1.1% were contaminated by Salmonella spp., 34.1% were contaminated by coliforms, and 26.2% were positive for E. coli. The results showed that trimming contributes to reducing significantly the bacterial total count at the site and that the bacterial load at this site was less important than that found on the brisket.     

Most probable number cultures for assessing Salmonella contamination of eviscerated broiler carcasses.

Rinse fluids collected from eight different lots of commercially processed broiler carcasses were cultured for salmonellae by a meat probable number method. Most probable number values of 80 or less were obtained from all carcasses in three of the eight lots, but two lots contained carcasses which yielded more than 1000 salmonellae. Similar numbers of salmonellae were recovered in repeated rinses of the same carcasses, suggesting that only a small proportion of the total population was recovered in each rinse. Five lots originated from flocks of known Salmonella status. More salmonella were recovered from carcasses which originated from flocks infected in the first week of life than from flocks infected at a later date. Carcasses from a flock which was processed immediately after a contaminated flock yielded more salmonellae than carcasses processed at the beginning of the day in a clean plant.     

Estimation of Salmonella prevalence on individual-level based upon pooled swab samples from swine carcasses

Pooling of samples might be an effective means to increase cost-effectiveness in routine surveillance. The present study assessed the effect on the sensitivity of detection of Salmonella when pooling swab samples from swine carcasses compared to individual analyses. A total of 18,984 samples from nine Danish swine abattoirs were collected during 1 year, covering 2017 slaughter days. At each abattoir, swab samples were taken on a daily basis from 10 carcasses randomly selected. From each carcass, an area of 3 cm x 100 cm was swabbed. Five of these samples were analysed individually and the other five were analysed as one pooled sample. Standard culture methods were used. A logistic regression model was built, where the response was whether a sample was Salmonella positive or not. The explanatory factors were abattoir, type of sampling (individual or pooled sample), and season of year 2000 (four quarters). The odds ratio (OR) of the effect of type of sampling in the logistic model accounting for abattoir and season was interpreted as the conversion factor between pooled and individual sample prevalence. The results of the individually analysed samples showed a low prevalence of Salmonella (1.4%). When Salmonella was isolated, mostly only one positive sample was found among the five individually analysed samples per slaughter day. On a few days >1 positive samples' were found (9 out of 2017 days approximately 0.4%). The pooled sample prevalence was 4.1%. Because the individual prevalence was low, the pooled sample prevalence would have been around five times higher than the individual-level prevalence-if there had been no loss of sensitivity. However, we found that due to loss of sensitivity the pooled prevalence was only three times higher (OR = 2.7; CI 2.0-3.7). Therefore, a conversion factor of 3 instead of 5 should be applied to calculate the individual prevalence from a pooled prevalence. This approach has been used in the national surveillance of Danish pork since 2001. The estimated conversion factor and accept of pooling samples do not necessarily apply to a population with a higher prevalence or to other types of samples (e.g. faeces or lymph nodes) or diagnostic procedures.     

Reduction of Salmonella and fecal contamination of pork during swine slaughter.

Experiments were designed to reduce Salmonella and fecal contamination of pork, using several sanitizing methods and agents. Sanitizing the hauling vehicle and holding pens with chlorine or quaternary ammonium compounds proved ineffective in reducing carcass contamination. When the eviscerator wore a plastic glove and sanitized his knife in 82-C water before using it on each carcass, contamination was reduced about 50%. Sanitizing the eviscerator's knife in 500-ppm chlorine solution adjusted to a pH of 6.0, or in 25-ppm iodine solution reduced contamination approximately 75%.     

Microbiological identification and analysis of swine tonsils collected from carcasses at slaughter

The primary objective of this 7-month study was to determine the prevalence of porcine pathogens of the tonsil of the soft palate of swine at slaughter. Additional objectives were to determine if sampling the carcasses of normal or abnormal hogs provided different microbiological profiles and if the slaughter plant provides a feasible sampling frame and environment for detecting and monitoring important pathogens in tonsils that have health implications for both swine and humans. A total of 395 samples were collected from 264 farms. Of these, 180 tonsils were collected from normal carcasses and 215 tonsils were collected from carcasses that were diverted to the hold rail. Laboratory testing included bacteriological culture and identification as well as real time-polymerase chain reaction (PCR) testing for porcine reproductive and respiratory syndrome virus (PPRSV) and immunohistochemistry (IHC) for porcine circovirus-2 (PCV-2). The most commonly isolated bacteria included: Streptococcus suis (53.7%), Arcanobacterium pyogenes (29.9%), Pasteurella multocida (27.3%), and Streptococcus porcinus (19.5%). Virus screening revealed evidence of PRRSV and PCV-2 in 22.0% and 11.9% of the samples, respectively. Salmonella Typhimurium and Yersinia enterocolitica were isolated in 0.5% and 1.8% of the samples, respectively. Tonsils collected from the hold rail were more likely to be positive for Staphylococcus hyicus [odds ratio (OR) = 7.51, confidence interval (CI) = 2.89 to 19.54], Streptococcus porcinus (OR = 9.93, CI = 4.27 to 23.10), and Streptococcus suis (OR = 2.16, CI = 1.45 to 3.24). Tonsils collected from abnormal carcasses were less likely to be positive for Staphylococcus aureus (OR = 0.05, CI = 0.005 to 0.482).     

Implementation of a validated HACCP system for the control of microbiological contamination of pig carcasses at a small abattoir

To guide the implementation of a Hazard Analysis Critical Control Point (HACCP) system at a small abattoir, the microbiological conditions of pig carcasses at various stages of processing were assessed by enumerating total aerobes, coliforms, and Escherichia coli in samples collected from randomly selected sites on the carcasses. Those data indicated that carcasses were contaminated with bacteria mainly during dehairing and operations on the head. When carcasses were pasteurized after head removal, the numbers of total aerobes on dressed carcasses were reduced by about 1 order and the numbers of coliforms and E. coli were reduced by more than 2 orders of magnitude. Implementation of an HACCP system on the basis of the microbiological data gave cooled carcasses with mean numbers of total aerobes < 100/cm2, and mean numbers of coliforms and E. coli about 1/1000 cm2.     

Breakdown severity during a bovine tuberculosis episode as a predictor of future herd breakdowns in Ireland

A retrospective cohort study of Irish cattle herds investigated whether the severity of a herd’s bovine tuberculosis (BTB) breakdown was a predictor of the hazard of a future BTB breakdown in that herd. Data on 10,926 herds not having had BTB in 1995 (the “non-exposed” group) were obtained using a 10% random sample from all herds without BTB in 1995. Data on 6757 herds that had a new BTB breakdown in 1995 (the “exposed” group) were obtained and categorized into five increasing exposure-severity classes based on the total number of standard reactors (to the single intra-dermal comparative cervical tuberculin test) detected during the breakdown. Exposed herds were deemed to be free of BTB after they passed a 6-month check test; non-exposed herds were deemed free as of the date of the first negative herd-test in 1995.

In the 5 years after 1995, 18% of the non-exposed herds had a BTB breakdown, whereas 31% of the exposed herds had a subsequent breakdown. Relative to the hazard for non-exposed herds, the hazard for the first future singleton standard reactor breakdown, was 1.6-times higher for exposed herds with only 1 standard reactor in 1995, and 1.8-times higher for those exposed herds with 4–8 standard reactors during the 1995 episode. When the outcome for future breakdowns was 2 or more standard reactors, the hazard ratios ranged from 1.6 for exposed herds with only 1 standard reactor in 1995 up to 2.9 in exposed herds with 8 or more standard reactors during the 1995 episode. The latter hazard ratio varied over time, decreasing to 1.7 after 3 years of risk. The hazard of a future BTB breakdown increased directly with number of cattle in the herd, a positive history of previous BTB in the herd, and the local herd prevalence of BTB. The presence of confirmed BTB lesions in reactor cattle was not predictive of the future breakdown hazard when the effects of other factors were controlled.     

A systematic review-meta-analysis of chilling interventions and a meta-regression of various processing interventions for Salmonella contamination of chicken

Context

The results of individual studies investigating the efficacy of chilling and other processing interventions on Salmonella prevalence or concentration in broiler chicken carcasses are inconsistent or contradictory.

Objective

Determine efficacy of chilling on reducing Salmonella prevalence or concentration on broiler carcasses using systematic review-meta-analysis, and explore sources of heterogeneity among studies investigating various processing interventions through meta-regression.

Data sources

A comprehensive search included electronic search in six databases, manual search of reference lists of topic-related articles, and consultation with five topic experts to assure that all relevant intervention research was identified.

Study inclusion

Primary intervention research, published in English, encompassing control, challenge, cohort, or before-and-after study designs investigating the efficacy of any chilling or other processing interventions on Salmonella prevalence or concentration in broiler chicken carcasses.

Risk of bias assessment and data extraction

Data pertaining to study methodology and reported results, chilling or other processing intervention parameters, populations sampled and outcomes measured were assessed for methodological soundness and extracted by two independent reviewers using pretested checklists.

Results

Random-effects meta-analyses of immersion chilling with chlorine (n = 9 trials), acetic acid (n = 16) and potable water (n = 13) trended towards reductions in the odds or log₁₀ CFU/ml of Salmonella. Significant heterogeneity (P-value ≤ 0.1 and I² > 25%) precluded the reporting of pooled summary effect estimates. Meta-regression of all processing interventions indicated that serotype, disinfectant type and treatment time and pH were significantly associated with studies reporting reductions in concentration while study design, population sampled, study setting, publication date, intervention and disinfectant type, and treatment pH were significantly associated with studies reporting reductions in prevalence. Methodological and reporting flaws were consistently observed in relevant intervention research as well as a lack of studies conducted under commercial conditions and using Salmonella concentration outcomes.

Conclusions

Chilling may be effective at reducing Salmonella concentration and prevalence, but significant heterogeneity precluded reporting of pooled summary effect estimates for many chilling interventions. Investigations into potential sources of heterogeneity among all processing interventions found that the use of other chemical disinfectants, such as organic acids and surfactants might result in larger reductions in Salmonella contamination than more commonly utilized oxidizing agents like chlorine.     

Evaluation of procedures to predict fat-free lean in swine carcasses

The objectives were to develop equations for predicting fat-free lean in swine carcasses and to estimate the prediction bias that was due to genetic group, sex, and dietary lysine level. Barrows and gilts (n = 1,024) from four projects conducted by the National Pork Board were evaluated by six procedures, and their carcass fat-free lean was determined. Pigs of 16 genetic groups were fed within weight groups one of four dietary regimens that differed by 0.45% in lysine content and slaughtered at weights between 89 and 163 kg. Variables in equations included carcass weight and measures of backfat depth and LM. Fat-free lean was predicted from measures of fat and muscle depth measured with the Fat-O-Meater (FOM), Automated Ultrasonic System (AUS), and Ultrafom (UFOM) instruments, carcass 10th-rib backfat and LM area (C10R), carcass last-rib backfat (CLR), and live animal scan of backfat depth and LM area with an Aloka 500 instrument (SCAN). Equations for C10R (residual standard deviation, RSD = 2.93 kg) and SCAN (RSD = 3.06 kg) were the most precise. The RSD for AUS, FOM, and UFOM equations were 3.46, 3.57, and 3.62 kg, respectively. The least precise equation was CLR, for which the RSD was 4.04 kg. All procedures produced biased predictions for some genetic groups (P < 0.01). Fat-free lean tended to be overestimated in fatter groups and underestimated in leaner ones. The CLR, FOM, and AUS procedures overestimated fat-free lean in barrows and underestimated it in gilts (P < 0.01), but other procedures were not biased by sex. Bias due to dietary lysine level was assessed for the C10R, CLR, FOM, and SCAN procedures, and fat-free lean in pigs fed the lowlysine dietary regimen was overestimated by CLR, FOM, and SCAN (P < 0.05). Positive regressions of residuals (measured fat-free lean minus predicted fat-free lean) on measured fat-free lean were found for each procedure, ranging from 0.204+/-0.013 kg/kg for C10R to 0.605+/-0.049 kg/kg for UFOM, indicating that all procedures overestimated fat-free lean in fat pigs and underestimated it in lean pigs. The pigs evaluated represent the range of variation in pigs delivered to packing plants, and thus the prediction equations should have broad application within the industry. Buying systems that base fat-free lean predictions on measures of carcass fat depth and muscle depth or area will overvalue fat pigs and undervalue lean pigs.     

Prevalence of salmonella and campylobacter contamination in manitoba Swine carcasses

Muscle samples from the neck and diaphragm and fecal samples were collected from five hogs from each of 50 lots of market hogs at three Manitoba abattoirs. Environmental samples were also collected. Each sample was tested for Salmonella contamination, and tissue and fecal samples were tested for Campylobacter.

Salmonella was isolated from 34 (4.1%) of 821 samples, with 17 of the isolates coming from one lot of hogs and their concurrent environment. Campylobacter was isolated from 175 (26.3%) of 666 samples. Fifty-five percent were Campylobacter coli and 45% were Campylobacter jejuni.

     

Urinary protein level determination as a rapid method for the detection of contamination of slaughtered swine

Reference is made to work undertaken by Stehle (1983) on rapid semiquantitative determination of urinary protein in pigs for slaughter to identify premortal strain and stress, with additional studies being conducted into the suitability of the method. The investigations performed for this study covered urinary protein samples from 59 living and 762 slaughtered pigs. The Biophan E paper strip test was applied to groups of animals, and, when compared to high-accuracy laboratory determination of urinary protein, it provided sufficiently accurate information on the presence of stress-related proteinuria. Its accuracy, however, proved to be insufficient, when individual animals were examined. The number of clearly stressed slaughter pigs was unexpectedly high, although the same animals had been rated clinically inconspicuous prior to slaughter. Brief rest period resulted in significant rise of stress. The Biophan E paper strip test was found to be suitable for instantaneous determination of stress and strain on pigs for slaughter.     

Impact of the Salmonella status of market-age pigs and the pre-slaughter process on Salmonella caecal contamination at slaughter

The aim of this study was to evaluate the impact of the pre-slaughter process on Salmonella caecal contamination of pigs at slaughter. An observational study was carried out in 2001 on 101 conventional farrow-to-finish pig farms. On each farm, one batch of contemporary pigs was followed from the end of the fattening period until slaughter. The Salmonella bacteriological status of the batches was assessed by environmental samples of faecal material. The serological Salmonella status was obtained on 30 individually identified market-age pigs using an indirect ELISA test. At the slaughterhouse, 25 g of caecal contents were taken from 10 of the identified pigs. Faecal and caecal material were analysed according to a classical bacteriological method. A questionnaire was designed to obtain information about the type of feeding during the fattening period (dry versus wet), the duration of fasting on the farm before leaving for the slaughterhouse, the duration of transport between the farm and the slaughterhouse, the holding time in lairage at the slaughterhouse and loading and unloading conditions on the farm and at the slaughterhouse. To assess the relationships between these factors and the Salmonella caecal status of the pigs and the batches, two logistic models were fitted at the individual and at the batch level, respectively. The first analysis was performed using a random effects logistic regression model. The second analysis was based on a cumulative logit model with a positive caecal rate classified into three classes as the outcome variable. The results showed that the Salmonella status of market-age pigs assessed on the farm either by serological or bacteriological examinations and the time spent in lairage before slaughtering played a crucial role on caecal contamination. In the light of these results, actions should be considered both on the farm and at the slaughterhouse to decrease the risk of Salmonella contamination of the caecal contents.     

Dynamics of Salmonella contamination in a commercial quail operation.

Control of carcass contamination requires knowledge of the source and dynamics of spread of Salmonella in commercial poultry production. We examined Salmonella contamination at a U.S. commercial quail operation. Pulsed-field gel electrophoresis (PFGE) was used to type isolates in order to trace Salmonella throughout this production environment. During a 6-mo survey, Salmonella serotypes hadar, typhimurium, typhimurium variant Copenhagen, and paratyphi were encountered within this poultry operation. Ninety-four percent of the Salmonella isolated from breeder and production houses and from carcass rinses belonged to Salmonella serotypes typhimurium variant Copenhagen and hadar. There were six distinct S. typhimurium variant Copenhagen genetic types, as identified by PFGE, present within this particular poultry operation. Seventy-nine percent of S. typhimurium variant Copenhagen identified from the environment of the breeder and production houses produced the same PFGE pattern. Thirty-eight percent of S. typhimurium Copenhagen isolated from carcass rinses and the breeder house shared the same PFGE DNA pattern. This study demonstrates the transmission of salmonellae throughout this production environment, from the breeders to their progeny and to the birds ultimately processed for human consumption.