N. Korsak

An Efficient Sampling Technique Used To Detect Four Foodborne Pathogens on Pork and Beef Carcasses in Nine Belgian Abattoirs

The method presented in this paper should prove useful in assessing the effectiveness of HACCP plans developed in slaughterhouses. Samples were collected by swabbing well-defined areas of pork and beef carcasses with sterile gauze. Between 160 and 420 half-carcasses were swabbed in each of nine pork or beef slaughterhouses. Swabs from five carcasses were placed in the same sterile Stomacher bag, constituting a single composite sample. Standard or validated analytical methods were used to isolate and characterize four foodborne pathogens. Salmonella spp., Listeria monocytogenes, Campylobacter spp., and verocytotoxin-producing E. coli were detected, respectively, in 27, 2, 2, and 14% of the pork samples and 0, 22, 10, and 5% of the beef samples. Of the 10 samples positive for E. coli O157, only one yielded an isolate confirmed to be enterohemorrhagic. Since Salmonella spp. appear as the main contaminant port (27%) and L. monocytogenes as the main containment of beef (22%), any slaughterhouse sampling plan should include testing for the former in the case of pork carcasses and for the latter in the case of beef carcasses. One should also test regularly for the presence of E. coli O157 and Campylobacter spp. in pork and beef abattoirs. The method presented here is an easy way to assess the contamination rate of carcasses at the end of the slaughtering process.

Salmonella contamination of pigs and pork in an integrated pig production system.

This paper describes the monitoring of Salmonella in a closed pig production system in Belgium over a 2-year period. A sampling scheme including animal feeds and carcasses was designed to cover the entire chain of production from farrow to finishing pigs. Salmonella was detected by a method based on the use of semisolid Rappaport-Vassiliadis as a selective medium. The serotypes of the isolated strains were determined, and the antibiotic resistance of these strains to six antibiotics was also investigated. Feeds were found to be more contaminated than expected (10.2%, 34 of 332 samples). The percentage of positive fecal samples for pregnant sows (8.1%, 11 of 135 samples) was significantly higher than that for young and lactating sows (2.9%, 11 of 378 samples) (P<0.05). The percentage of positive samples for colon contents collected at the slaughterhouse (47.3%, 88 of 186 samples) was significantly higher than that for feces collected during the fattening stage (5.6%, 18 of 320 samples) (P<0.001). For carcass swab samples, the observed prevalence was 11.2% (17 of 152 samples). On farms, Salmonella recovery levels were higher for overshoe samples than for fecal samples, except for pregnant sows. Salmonella Typhimurium was the most frequently isolated serotype (32.2%, 55 of 171 samples), while Salmonella Brandenburg was predominant in the colon contents collected at the abattoir (21.4%, 18 of 84 samples). Feeds harbored a wide diversity of serotypes of minor epidemiological significance. Of 55 isolated strains of Salmonella Typhimurium, 11 (20%) were resistant to tetracycline, ampicillin, choramphenicol, streptomycin, trimethoprim, and nalidixic acid (R Type TeAmCSNa), while 12 (21.8%) were resistant to all of these antibiotics except nalidixic acid (R Type TeAmCS). The majority of Salmonella Typhimurium strains that exhibited resistance to more than four antimicrobial agents were characterized as Salmonella Typhimurium DT104 or as being closely related to Salmonella Typhimurium DT104 (7 of 12 isolates). In conclusion, our system of surveillance is effective in identifying most points of contamination in the production chain and will be useful in ongoing efforts to develop a Salmonella-free production system.

Microbiota characterization of a Belgian protected designation of origin cheese, Herve cheese, using metagenomic analysis.

Herve cheese is a Belgian soft cheese with a washed rind, and is made from raw or pasteurized milk. The specific microbiota of this cheese has never previously been fully explored and the use of raw or pasteurized milk in addition to starters is assumed to affect the microbiota of the rind and the heart. The aim of the study was to analyze the bacterial microbiota of Herve cheese using classical microbiology and a metagenomic approach based on 16S ribosomal DNA pyrosequencing. Using classical microbiology, the total counts of bacteria were comparable for the 11 samples of tested raw and pasteurized milk cheeses, reaching almost 8 log cfu/g. Using the metagenomic approach, 207 different phylotypes were identified. The rind of both the raw and pasteurized milk cheeses was found to be highly diversified. However, 96.3 and 97.9% of the total microbiota of the raw milk and pasteurized cheese rind, respectively, were composed of species present in both types of cheese, such as Corynebacterium casei, Psychrobacter spp., Lactococcus lactis ssp. cremoris, Staphylococcus equorum, Vagococcus salmoninarum, and other species present at levels below 5%. Brevibacterium linens were present at low levels (0.5 and 1.6%, respectively) on the rind of both the raw and the pasteurized milk cheeses, even though this bacterium had been inoculated during the manufacturing process. Interestingly, Psychroflexus casei, also described as giving a red smear to Raclette-type cheese, was identified in small proportions in the composition of the rind of both the raw and pasteurized milk cheeses (0.17 and 0.5%, respectively). In the heart of the cheeses, the common species of bacteria reached more than 99%. The main species identified were Lactococcus lactis ssp. cremoris, Psychrobacter spp., and Staphylococcus equorum ssp. equorum. Interestingly, 93 phylotypes were present only in the raw milk cheeses and 29 only in the pasteurized milk cheeses, showing the high diversity of the microbiota. Corynebacterium casei and Enterococcus faecalis were more prevalent in the raw milk cheeses, whereas Psychrobacter celer was present in the pasteurized milk cheeses. However, this specific microbiota represented a low proportion of the cheese microbiota. This study demonstrated that Herve cheese microbiota is rich and that pasteurized milk cheeses are microbiologically very close to raw milk cheeses, probably due to the similar manufacturing process. The characterization of the microbiota of this particular protected designation of origin cheese was useful in enabling us to gain a better knowledge of the bacteria responsible for the character of this cheese.

Salmonella surveillance and control at post-harvest in the Belgian pork meat chain

Salmonella remains the primary cause of reported bacterial food borne disease outbreaks in Belgium. Pork and pork products are recognized as one of the major sources of human salmonellosis. In contrast with the primary production and slaughterhouse phases of the pork meat production chain, only a few studies have focussed on the post-harvest stages. The goal of this study was to evaluate Salmonella and Escherichia coli contamination at the Belgian post-harvest stages. E. coli counts were estimated in order to evaluate the levels of faecal contamination. The results of bacteriological analysis from seven cutting plants, four meat-mincing plants and the four largest Belgian retailers were collected from official and self-monitoring controls. The prevalence of Salmonella in the cutting plants and meat-mincing plants ranged from 0% to 50%. The most frequently isolated serotype was Salmonella typhimurium. The prevalence in minced meat at retail level ranged from 0.3% to 4.3%. The levels of Salmonella contamination estimated from semi-quantitative analysis of data relating to carcasses, cuts of meat and minced meat were equal to -3.40+/-2.04 log CFU/cm(2), -2.64+/-1.76 log CFU/g and -2.35+/-1.09 log CFU/g, respectively. The E. coli results in meat cuts and minced meat ranged from 0.21+/-0.50 to 1.23+/-0.89 log CFU/g and from 1.33+/-0.58 to 2.78+/-0.43 log CFU/g, respectively. The results showed that faecal contamination still needs to be reduced, especially in specific individual plants.

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

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

Risk factors for Salmonella and hygiene indicators in the 10 largest Belgian pig slaughterhouses.

A survey was conducted to collect data on Salmonella prevalence, Escherichia coli counts (ECCs), and aerobic bacteria colony counts (ACCs) on pig carcasses after chilling at the 10 largest Belgian pig slaughterhouses during 2000 through 2004. Potential risk factors of contamination associated with production parameters, technical descriptions of the installations, and cleaning and disinfection methods were assessed during investigations in the slaughterhouses. These variables were used first in a univariate analysis and then were extended to a multivariate analysis with a logistic mixed regression model for Salmonella and a linear mixed model for ECCs and ACCs with slaughterhouses as the random effect. The results indicated high variability concerning Salmonella contamination among the 10 slaughterhouses, with prevalence ranging from 2.6 to 34.3% according to the area of origin. The median ECC and median ACC ranged from -0.43 to 1.11 log CFU/cm2 and from 2.37 to 3.65 log CFU/cm2, respectively. The results of the logistic and linear regressions revealed that some working practices such as scalding with steam, second flaming after polishing, and complete cleaning and disinfection of the splitting machine several times a day were beneficial for reducing Salmonella prevalence, ECCs, and ACCs. Changing the carcass hooks just before chilling, using water as the cleaning method, and a higher frequency of disinfection of the lairage seemed to be protective against E. coli in the multivariate mixed linear model. The monitoring of critical points, slaughterhouse equipment, good slaughtering practices, and effective washing and disinfection are the keys to obtaining good microbiological results.

Assessing Interventions by Quantitative Risk Assessment Tools To Reduce the Risk of Human Salmonellosis from Fresh Minced Pork Meat in Belgium

The risk of human salmonellosis through the consumption of minced pork meat in Belgium was assessed via a modular risk model covering pork meat production from lairage to human consumption. The main goal of the model was to give concrete options to reduce effectively the risk of human salmonellosis through the consumption of minced pork meat. These options (scenarios) were elaborated with reference to the international situation and the literature to give concrete and realistic possibilities for improving the microbiological quality of pork meat and to reduce the number of human salmonellosis cases per year in Belgium. The model estimates 15,376 cases of human salmonellosis per year in Belgium due to the consumption of minced pork meat. The results of the scenarios showed that the risk of human salmonellosis could be significantly reduced by efforts all along the pork meat production chain but also by efforts made by consumers. The responsibility of food business operators for the pork meat production chain is high in relation to the microbiological quality of meat delivery, especially at the slaughterhouse. Consumers also need to be aware of good hygiene practices during preparation of the meat at home. Cross-contamination with raw food can be avoided by changing the habits and the behavior of the household cook. The results of these scenarios would be useful for the food business operators involved in the pork meat chain and for public health authorities.

Comparison of four different methods for Salmonella detection in fecal samples of porcine origin

Performances of four detection methods were evaluated for recovery of Salmonella spp. in naturally contaminated fecal specimens of porcine origin. The NMKL 71 method consisted of enrichment in Rappaport-Vassiliadis broth and plating on xylose-lysine-desoxycholate medium, whereas the SP-VG-M002 method relied on a Diasalm enrichment followed by streaking on xylose-lysine-tergitol 4 agar (XLT-4). The VIDAS SLM method was composed of double enrichment in Muller-Kauffmann tetrathionate broth and in M broths before processing in a VIDAS device. If the results were positive, the VIDAS ICS immunoenrichment was performed and the result transferred onto three different selective media. The VIDAS ICS protocol is an immunoconcentration step followed by plating on XLT-4. Seventy-eight samples were tested with all four methods simultaneously, leading to 34 positive samples with at least one method. For this assay, VIDAS SLM revealed 31 positive samples (91.2%), whereas the average positive percentage of the three other methods was 37.3% (P < 0.001). Two-paired comparisons with the VIDAS SLM method were also performed. McNemar values were systematically highly significant (P < 0.001). The proportion of agreement was significantly inferior (P < 0.05) for the comparison of VIDAS ICS and VIDAS SLM (68.7%) compared with the two other paired comparisons (average percentage, 81.5%). The conclusion reached by this trial is that VIDAS SLM significantly improves the recovery of Salmonella in naturally contaminated fecal specimens. For the paired-comparisons, NMKL 71 and SP-VG-M002 were comparable in terms of efficiency, whereas the VIDAS ICS protocol, as established by the manufacturer for food samples only, seemed less efficient than the other two.

Clostridium difficile from food and surface samples in a Belgian nursing home: An unlikely source of contamination

This study investigates the contamination of foods and surfaces with Clostridium difficile in a single nursing home. C. difficile PCR-ribotype 078 was found in one food sample and in none of the tested surfaces. These results indicate that food and surfaces are an unlikely source of C. difficile infection in this setting.

Clostridium difficile in beef cattle farms, farmers and their environment: assessing the spread of the bacterium

In recent years, several studies have described the presence of Clostridium difficile in healthy and diarrhoeic farm and domestic animals. In pigs and cattle, the isolation of some PCR-ribotypes associated with human infection, especially PCR-ribotypes 014 and 078, has led us to hypothesize about the zoonotic transmission of C. difficile infections. If these animals are reservoirs of C. difficile, farmers in close contact with their animals are particularly at risk of acquiring and spreading the bacterium. This study investigates the presence of C. difficile in closely associated populations, beef cattle and farmers, as well as in the animal feed, manure and dust in five different farms in Belgium. C. difficile was isolated from calves and cattle with a prevalence varying between 5.5% and 11.3%. Furthermore, all of the isolates were toxigenic. An important age and breed effect was observed in the colonization of C. difficile. For age, there was a higher probability of colonization in calves of less than 6 months in age than in cattle over 11 months of age. For the type of breed a higher prevalence of the bacterium was detected in the Limousin breed than in the Belgian Bleu breed. By contrast, none of the human and animal feed samples tested positive for C. difficile. The results obtained indicate a persistent animal reservoir of C. difficile, but an indirect dissemination to humans, probably via the environment.