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

Selective citation in the literature on the hygiene hypothesis:A citation analysis on the association between infections and rhinitis

Objective Our objective was to assess the occurrence and determinants of selective citation in scientific publications on Strachan's original hygiene hypothesis. His hypothesis states that lack of exposure to infections in early childhood increases the risk of rhinitis. Setting Web of Science Core Collection. Participants We identified 110 publications in this network, consisting of 5551 potential citations. Primary and secondary outcome measures Whether a citation occurs or not, measured and analysed according to the preregistered protocol. Results We found evidence for citation bias in this field: publications supportive of the hypothesis were cited more often than non-supportive publications (OR adjusted for study design [adjOR] 2.2, 95% CI 1.6 to 3.1), and the same was the case for publications with mixed findings (adjOR 3.1, 95% CI 2.2 to 4.5). Other relevant determinants for citation were type of exposure, specificity, journal impact factor, authority and self-citation. Surprisingly, prospective cohort studies were cited less often than other empirical studies. Conclusions There is clear evidence for selective citation in this research field, and particularly for citation bias

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

Quantitative exposure to livestock-associated MRSA ST398 of pig slaughterhouse workers

Objectives: To quantify livestock-associated MRSA (LA-MRSA) exposure to workers in pig slaughterhouses and assess associated risk factors for carriage in slaughterhouse workers. Methods: A cross-sectional study in three Dutch pig slaughterhouses was undertaken. Nasal swabs of 341 participants, surface wipes, air, and glove samples were screened for presence of MRSA. MRSA was quantitatively determined on gloves and in air samples by culturing and real-time PCR

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

The use of random amplified polymorphic DNA analysis as a simple tool to distinguish between salmonella isoaltes ina n epidemiologic research

In the Netherlands Salmonella is, together with Campylobacter, one of the most important causes of bacterial foodborne infections. Although poultry is recognised as the major source of salmonellosis in man, pork also contributes to the human cases of salmonellosis (Van de Giessen, 1996)

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

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