Origin of Listeria monocytogenes on meat products

Listeria monocytogenes is a relevant food safety hazard in ready to eat products. Inactivation during processing, prevention of recontamination and control of multiplication are the main instruments to secure the safety of meat products. Intensive microbiological monitoring of products and the production environment are valuable tools to assess the level of control in a meat processing plant. During the course of a year all isolates found during hygiene monitoring at a meat processing plant were stored at -70 degrees Celsius. A total of 94 L. monocytogenes isolates have been analyzed by pulsed-field gel electrophoresis (PFGE) and were divided into 30 different types

Case study: Tuberculination, serology and bacteriology of sows at a farrowing unit suspected of an infection with Mycobacterium avium

Mycobacterium avium (MA) is considered a zoonotic hazard in pork. Herds delivered at slaughter showing gross lesions indicative of a mycobacterial infection, eg. specific abcesses in lymphoreticular tissue, were bacteriologically positive for MA. A risk factor analysis revealing different possible sources of primary infection was carried out at farms supplying these pigs. Also the common farrowing farm supplying the piglets to these farms was taken into account as a possible source of infection. Intradermal tuberculin testing, serology and tissue sampling was carried out on the sows and finishing pigs

Selection of finishing pig herds with a low Salmonella prevalence for logistic slaughtering

The aim of this study was to select 50 herds with a low Salmonella-contamination rate. Per herd 40 blood samples were collected which had to be negative for antibodies against Salmonella. Infection of the pigs at the abattoir was measured by culturing tonsils for Salmonella. The results showed that not enough herds could be selected when the original criteria were applied. Less strict criteria had to be applied. We conclude from this trial that it is possible to select herds with a lower Salmonella-prevalence resulting in a lower introduction of Salmonella into the abattoir. Strict criteria must be applied to select herds with a minimal risk of being Salmonella-positive

Comparison of an excision and a sponge sampling method for measuring salmonella contamination of pig carcasses

The aim of this study was to determine if an excision sampling method and a sponge sampling method give comparable results when trying to isolate salmonella from pig carcasses. During ten sampling days in one abattoir in total 312 carcasses were sampled; each carcass was sampled with both sampling methods to get paired observations. The number of salmonella positive excision samples (31 of 312) was significantly higher (P=0.00013) than the number of salmonella positive sponge samples (9 of 312). Sensitivity of the sponge method compared to the excision method was 6.5% and the comparability of both tests was low (kappa value was 0.08). As it seems that salmonella contamination levels of fresh pork are highly underestimated with the actually used sampling methods, the authors recommend that EU-authorities prescribe a destructive salmonella test for monitoring pig carcasses after slaughter in all EU-countries or a swab/sponge method with a comparable sensitivity

Reducing liver lesion incidence in the Dutch pork supply chain

Livers with lesions are an cmportant quality aspect among slaughter pig producers and slaughterhouses. Total losses of non-marketable livers with lesions, lower growth and higher feed intake of pigs in the Netherlands in 2003 were estimated at €3.5 million. The major cause of liver lesions is the roundworm Ascaris suum. Worm treatment on the farm can be effective in reducing liver lesions. Before July 2004 an insurance with a fixed premium for each slaughtered pig was in place in the Netherlands to compensate slaughterhouses for pathological lesions. Individual pig producers had low incentcves to take control measures. In July 2004 a new incentive mechanism was introduced: a reduction in the payment of €1 for each pig with a liver lesion. Thcs placed the financcal burden of levers with lesions on the producer, thereby increasing incentives to treat roundworm infections. We analysed the data of 1,104 farms wcth 55,802 deliveries from 2003 to 2006. The mean liver lesion incidence decreased from 8% in 2003 when a collectcve insurance was in place to 5% in 2006, after the change to the price reduction. Of the producers, 68% reduced liver lesion mcidence. Of the producers with an increased incidence, 83% showed a low increase (less than 5%). We conclude that the price reduction was effective in reducing the mean incidence of liver lesions, although large differences between individual producers exist. Further research is needed to determme what causes these large differences

Case studies: Tuberculination in pig herds suspected of infection with Mycobacterium avium

Mycobacterium avium, both subspecies hominissuis (MAH) and subsp avium (MAA), are considered a significant zoonotic hazard in pigs. Therefore special attention is given to detect the presence of this hazard in pigs during post mortem meat inspection. Herds delivered at slaughter were monitored on blood antibodies against MAH. Herds with an antibody response against a MAH infection were visited. Initially a questionnaire assessing relevant risk factors for MAH was applied

Determinants of Citation in Epidemiological Studies on Phthalates:A Citation Analysis

Citing of previous publications is an important factor in knowledge development. Because of the great amount of publications available, only a selection of studies gets cited, for varying reasons. If the selection of citations is associated with study outcome this is called citation bias. We will study determinants of citation in a broader sense, including e.g. study design, journal impact factor or the funding source of the publication. As a case study we assess which factors drive citation in the human literature on phthalates, specifically the metabolite mono(2-ethylhexyl) phthalate (MEHP). A systematic literature search identified all relevant publications on human health effect of MEHP. Data on potential determinants of citation were extracted in duplo. Specialized software was used to create a citation network, including all potential citation pathways. Random effect logistic regression was used to assess whether these determinants influence the likelihood of citation. 112 Publications on MEHP were identified, with 5684 potential citation pathways of which 551 were actual citations. Reporting of a harmful point estimate, journal impact factor, authority of the author, a male corresponding author, research performed in North America and self-citation were positively associated with the likelihood of being cited. In the literature on MEHP, citation is mostly driven by a number of factors that are not related to study outcome. Although the identified determinants do not necessarily give strong indications of bias, it shows selective use of published literature for a variety of reasons

Feed as a vehiculum of salmonella in pigs

Competitive exclusion for the prevention of intestinal colonization by Salmonella is an attractive approach that showed promise in some animal species. Nurmi and Rantala demonstrated that the susceptibility of broiler chicks to colonization by Salmonella spp. was due to the delayed establishment of intestinal microflora in chickens. They also showed that Salmonella spp. infections could be prevented by feeding the chicks with anaerobic cultures of normal adult fowl flora (Nurmi et all973). Although the efficacy of competitive exclusion has been demonstrated in chickens, little work has been done with other species. Mucosal competitive exclusion was recently used to control Salmonella in swine and tends to reduce the presence of Salmonella in tissues (Fedorka-Cray et al, 1996). Other studies have used well characterized lactic acid bacteria. Shanhani et al ( 1977) reported that lactobacilli could inhibit the growth of Salmonella in vitro. Competitive exclusion of E. coli and other pathogens by lactobacilli and their cell wall fragments has been demonstrated on human cells in culture by several other workers (Chan et al 1985, Coconnier et al. 992). The most commonly used and reported probiotics include lactobacilli (L. acidophilus, L. casei, L. bulgaricus), and bifidobacteria (B. bifidum, B.longum, B. breve, B. infantis) (Saavedra J.M. 1995). One of the proposed mode of action of such microbial preparations is that the component organisms may colonize the intestine, inhibit the growth of pathogenic bacteria such as salmonellae, and establish a more favourable environment in the host animal (Jin L.Z. et al1996). Carrier state of Salmonella in swine productions may result in contamination of meat. Efforts are now being made to control Salmonella infection at farm-level and probiotics seems to be a practical and safe approach. The objective of this experiment was to determine if probiotics used as feed additive influence the colonization of tissues and the shedding of Salmonella typhimurium in experimentally infected pigs

Tonsils of slaughtered pigs as marker sample for Salmonella positive pork

Pork is responsible for approximately 15% of all cases of salmonellosis in humans in Western Europe and North America (I). To reduce the prevalence of pork-borne salmonellosis in man, it is important that carcasses of slaughtered pigs and other edible pork products do not contain salmonella after the slaughter process. As long as it is not possible to avoid contamination of pork with salmonella, the contamination level should be as low as reasonably achievable. In order to reach this situation, contaminated carcasses should be identified, so that this meat can be processed (e.g. heated) to eliminate the safety risks. For this reason it can be useful to investigate a sample, which can be collected easily and is able to predict if salmonella is present on the carcass after slaughter

Lactic acid and acetic acid reduce Salmonella in fermented pig feed

To reduce contamination of pork with salmonella, a reduction of the prevalence of salmonella in the whole pork production chain is needed. At farm level the presence of endemic (\u27house flora\u27) salmonellae in fattening pigs is recognized as a major risk factor. Pig feed is considered to be involved in the transmission, survival and multiplication of these salmonellae. Pigfarms that supply their pigs with fermented pig feed have a lower prevalence, compared to farms that supply their pigs dry feed (3). In an earlier experiment we have shown that fermentation of feed can reduce the numbers of Salmonella typhimurium in feed . This paper reports the effect of these acids, on the survival of Salmonella typhimurium in brain heart infusion broth. Acid concentrations present after 3 days of fermentation were used in these in vitro experiments