Salmonella in meat from hunted game: A Central European perspective

The occurrence of Salmonella in meat from game hunted in Europe is reviewed, with a focus on Central Europe. Prevalence in fecal samples is different according to region and game species, ranging from < 5 (wild ruminants) to ca. 20% (wild boar). The pathogen is rarely recovered from carcasses or meat cuts of wild ruminants (< 1%). Prevalences on wild boar carcasses have been reported to range from < 1 to ca. 7%, the tonsils presumably constituting a main reservoir on the eviscerated carcass. On meat cuts from game, recent German and EU (EFSA) reports indicate a prevalence of < 1%. A number of Salmonella enterica serovars can be isolated, with highest prevalences of S. Typhimurium and S. Enteritidis. Persistence of these pathogens in wildlife is a less pressing issue for biology and wildlife conservation than for public health experts, which has been recognized in the framework of zoonoses legislation. On one hand, wildlife is exposed to salmonellae originating from farm animals and humans, and on the other hand, game can be a source of Salmonella in farm animals. Breeding game under intensified conditions (farmed game) as well as extensive breeding of farm animals, notably pigs, can create new epidemiological situations. The pathway of Salmonella from intestinal content of the live animal to individual meat cuts can be described in qualitative terms, yet the relative contribution of the various factors remains to be quantified, which complicates proper risk assessment. Control of Salmonella in the game meat chain is in part based on Good Hygiene Practice from killing and evisceration to chilling and skinning, whereas more detailed data are needed in order to allow risk-based meat inspection.     

Epizootiology and Control Measures for Salmonella in Pigs

Pigs and pork meat products are often causes of Salmonella in humans. Salmonella can enter the human food chain at any part of the meat production process. Contamination of pork can be reduced by lowering the contamination of pigs at primary production. Production of “Salmonella free pigs” will reduce the risk of this zoonozis in people. It is possible to determine the serological status of pig farms. Prevention of Salmonella in humans should aim at: prevention of entrance of Salmonella to the pig farm, reduction of the number of infected animals and stopping the spreading of microorganism.     

Risk of salmonellosis from consumption of almonds in the North American market

Salmonellosis outbreaks from consumption of raw almonds in 2001 and 2004 led to regulations that require mandatory treatment of almonds sold in North America to give a minimum 4-log reduction of Salmonella. This study aims to: 1) assess the risk of salmonellosis associated with almond consumption in North America, with current treatments in effect; 2) determine the resilience of the current production system to increases in prevalence or concentration of Salmonella on almonds; 3) assess the impact of treating less than 100% of the crop; and 4) investigate conditions that could explain the number of cases associated with the 2001 outbreak. Risk was assessed using a Monte Carlo simulation, based on an established dose–response relationship. Data for almond amounts sold, Salmonella prevalence and concentration on almonds, storage time and temperature at different handling steps, population reductions during storage at various temperatures and with different treatments, and consumer handling were based on data from published sources and almond industry or academic expert opinion. What-if scenarios were evaluated for Salmonella prevalence varying from 1 to 65%, concentrations of Salmonella varying from 1 to 120 MPN/100 g, and portions of untreated crop varying from 0 to 10%. The estimated incidence of salmonellosis in North America from almonds as currently treated is on average 0.008 cases per billion servings (with an estimated 6.6 billion servings consumed annually). Increases in Salmonella prevalence to 25%, mean concentrations above 25 MPN/100 g, or leaving 0.05% of the crop untreated all resulted in an arithmetic mean risk greater than 1 case/year (with geometric means remaining below 1 case/year for all variables). Assuming 4000 kg at a prevalence of 65% (observed in recalled lots) and an average concentration of 120 MPN/100 g in raw almonds (back calculated from levels in recalled almonds) predicted over the 2800 cases estimated for the 2001 outbreak. Applying a 4-log reduction to these almonds reduced the average number of predicted cases to less than a single case. The current regulation is effective in maintaining the risk of salmonellosis from consumption of almonds below an arithmetic mean of 1 case/year, although significant increases in either prevalence or concentration, or small increases in proportion of untreated almonds would frequently lead to exceeding this threshold.     

The role of transport,lairage and slaughter processes in the dissemination of Salmonella spp. in pigs in Ireland

Salmonella is an important foodborne pathogen worldwide and is commonly isolated from pigs and pig products in Ireland. Pigs, reared in an environment free of Salmonella spp. or with low levels of infection, may acquire infection or become contaminated during transport, lairage or post-slaughter. The main objective of this study was to determine the role of the abattoir as a potential factor that contributes to the dissemination of Salmonella spp. in slaughter pigs from herds with a low Salmonella seroprevalence (≤ 10%). A total of 128 pigs from eight herds were monitored from farm through the slaughter process in three separate abattoirs. The prevalence of Salmonella spp. was determined in samples collected from trucks, lairage pens and the slaughterline before pigs entered, from pigs after slaughter (caecal contents and ileocaecal lymph nodes) and carcass surfaces post-evisceration. Isolates were characterised by serotype, phage type and pulsed-field gel electrophoresis (PFGE) patterns. Of the swabs taken from the trucks, lairage and slaughterline, before the pigs entered, 4.3% (3/70), 80% (64/80) and 16.7% (4/27) were positive for Salmonella spp., respectively. The proportion of pigs showing serological evidence of infection was 3.1% (4/128). Salmonella spp. were isolated from the ileocaecal lymph nodes and caecal contents of 14.8% (19/128) and 11.7% (15/128) of pigs, respectively, and 13/128 (10.2%), 5/128 (3.9%), 2/111 (1.8%) and 8/111 (7.2%) carcass swabs pre wash, post wash, post chill and belly-strip samples, respectively, were Salmonella-positive. There was only slight agreement between serological and bacteriological data at the pig level. Salmonella isolates from 45% of all positive pig samples and 82% of positive carcass samples were indistinguishable, based on PFGE patterns, from salmonellae isolated from the lairage and slaughterline. Based on these results it is concluded that the lairage and the slaughterline provide a substantial source for Salmonella contamination of pigs and carcasses.     

Effect of organic pig production systems on performance and meat quality

The present study was carried out to establish knowledge of consequence for setting up guidelines of importance for production of competitive organic pork of high quality. Performance and meat quality characteristics were compared between three organic pig production systems based on indoor housing with access to an outdoor area and a Danish conventional indoor system including 100% concentrate during the finishing feeding stage.The three organic systems used the following three feeding regimes: 100% organic concentrate according to Danish recommendations, 70% organic concentrate (restricted) plus ad libitum organic barley/pea silage and 70% organic concentrate (restricted) plus ad libitum organic clover grass silage, respectively.With exception of a slightly lower daily gain in organic pigs fed 100% concentrate, no significant difference was found in performance and meat quality characteristics compared with results obtained in the conventional system. In contrast and independent of roughage used, organic pigs raised on 70% concentrate had a significant reduction in daily gain (P < 0.001) compared with pigs raised on 100% concentrate, despite the fact that no difference in feed conversion rate was seen between the tested production systems. However, the percentage of leanness increased significantly in meat from organic pigs raised on 70% concentrate plus roughage compared with meat from pigs given 100% concentrate. This was reflected in higher yield (weight) of lean cuts and lower yield of cuts with high fat content from pigs fed 70% concentrate plus roughage. In general, organic feeding resulted in a significantly higher content of polyunsaturated fatty acids in the back fat (1.8%), which increased further when restricted feeding plus roughage (4%) was used. Restricted concentrate feeding gave rise to a decrease in tenderness compared with pork from pigs fed 100% concentrate.     

Occurrence of methicillin-resistant Staphylococcus aureus in dairy cattle herds,related swine farms,and humans in contact with herds

In this study we investigated the circulation of methicillin-resistant Staphylococcus aureus (MRSA) in 2 dairy cattle farms (farm A and B), previously identified as MRSA-positive in bulk tank milk samples, and epidemiologically related to swine farms. Collected specimens included quarter milk samples and nasal swabs from dairy cows, pig nasal swabs collected at both the farm and slaughterhouse level, environmental dust samples, and human nasal swabs from the farms’ owners and workers. The prevalence of MRSA was estimated at the herd level by testing quarter milk samples. The prevalence of MRSA was 4.8% (3/63; 95% confidence interval = 0–10.2%) and 60% (33/55; 95% confidence interval = 47.05–72.95) in farm A and B, respectively. In farm A, MRSA was also isolated from humans, pigs sampled at both farm and slaughterhouse level, and from environmental samples collected at the pig facilities. The dairy cattle facilities of farm A tested negative for MRSA. In farm B, MRSA was isolated from environmental dust samples in both the cattle and pig facilities, whereas nasal swabs collected from cows and from humans tested negative. Sixty-three selected MRSA isolates obtained from different sources in farm A and B were genetically characterized by multilocus sequence typing, spa-typing, ribosomal spacer-PCR, and also tested for the presence of specific virulence genes and for their phenotypical antimicrobial susceptibility by broth microdilution method. Different clonal complex (CC) and spa-types were identified, including CC398, CC97, and CC1, CC already reported in livestock animals in Italy. The MRSA isolates from quarter milk of farm A and B mostly belonged to CC97 and CC398, respectively. Both lineages were also identified in humans in farm A. The CC97 and CC398 quarter milk isolates were also identified as genotype GTBE and GTAF by ribosomal spacer-PCR respectively, belonging to distinct clusters with specific virulence and resistance patterns. The GTBE and GTAF clusters also included swine, environmental, and human isolates from both farms. A high heterogeneity in the genetic and phenotypic profiles was observed in environmental isolates, in particular from farm B. These results demonstrate the possibility of a dynamic sharing and exchange of MRSA lineages or genotypes between different species and farm compartments in mixed-species farms. The risk of transmission between swine and related dairy cattle herds should be considered. Our findings also confirm the zoonotic potential of livestock-associated MRSA and underline the importance of applying biosecurity measures and good hygiene practices to prevent MRSA spread at the farm level and throughout the food production chain.     

Comparison of antimicrobial resistance patterns and phage types of Salmonella Typhimurium isolated from pigs,pork and humans in Belgium between 2001 and 2006

Infections with non-typhoid Salmonella represent a major problem in industrialized countries.The emergence and spread of antimicrobial-resistant pathogens, among them Salmonella, has become a serious health hazard worldwide. One of the most commonly isolated non-typhoid Salmonella serovars in pigs, pork and humans is Salmonella Typhimurium. In this study the comparison of the incidences of resistance to nine antimicrobials, resistance patterns and phage types between S. Typhimurium isolated from pigs (n = 581), pork (n = 255) and humans (n = 1870) in Belgium in the period 2001 to 2006 was performed.Resistance to the antimicrobials ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline was frequently observed and varied between 23.5% and 83.1%. Resistance ranged from 15.6% to 20.7% for the combination trimethoprim–sulfonamides and from 3.4% to 5.8% for nalidixic acid. Resistance to the critical important antimicrobials cephalosporins and fluoroquinolones was found sporadically (≤ 1.2%). Resistance to the different antimicrobials was observed to be similar in S. Typhimurium isolates from the various origins. Twenty-seven antimicrobial resistance patterns representing in total 75.2%, 89.0% and 89.6% of the isolates from pigs, pork and humans respectively were found to be common among the three groups and 73 combinations antimicrobial resistance pattern/phage type were found to be common among pork and human isolates, representing 70.1% of the pork isolates and 51.0% of the human isolates. The high percentage of isolates that have a common resistance pattern, and in a less pronounced way a common combination phage type/resistance pattern, are in agreement with the hypothesis of transfer of antimicrobial resistant Salmonella from pigs via the consumption of pork to humans as one of the possible pathways. The most prevalent combination in Belgium within both the pork isolates (7.4%) and the human isolates (13.2%) was S. Typhimurium DT104 resistant to ampicillin, chloramphenicol, streptomycine, sulfonamides and tetracycline.     

A systematic review and meta-analysis of the effectiveness of biosecurity and vaccination in reducing Salmonella spp. in broiler chickens

Our objective was to estimate the effectiveness of vaccination and biosecurity on the prevalence of Salmonella spp. in broiler chickens using systematic review and meta-analysis. A comprehensive search of the global primary literature was conducted in: Current Contents (1999–2009), Agricola (1924–2009), MEDLINE (1860–2009), Scopus (1960–2009), CAB (1913–2009), and Centre for Agricultural Bioscience Global Health (1971–2009). The search algorithm was (Salmonell*) AND (chicken* OR chick* OR poultry* OR broiler* OR gallus*). Additional studies were identified by contacting five topic experts and hand-scanning bibliographies of recent review articles and a recently published textbook. Studies were included if they were English language and investigated the effects of vaccination and biosecurity on the prevalence of Salmonella spp. in broiler chickens. All study design types were included. Data extraction and methodological assessment were conducted by two reviewers independently. All meta-analyses were based on random-effects models. For biosecurity, sixteen challenge studies (n = 137 treatment-control comparisons) and one controlled study (n = 2) met the inclusion criteria. Significant heterogeneity (Cochran's Q-statistic, p < 0.001) was observed among biosecurity challenge studies examining hydrogen peroxide or polyhexamethylenebiguanide hydrochloride applied to hatching eggs, making it inappropriate to present a summary effects measure. For vaccination, 19 challenge studies (n = 226) and three controlled studies (n = 10) met the inclusion criteria. Among live Salmonella Typhimurium vaccine challenge studies heterogeneity was not significant (p = 0.138). Vaccination with a live Salmonella Typhimurium reduced the risk of Salmonella cecal colonization in the treated broiler group by 35 out of 1000 broilers when compared to the control group (OR = 0.21; 95% CI = 0.06–0.77) and this effect was significant (p = 0.018). One biosecurity study (n = 2 treatment-control comparisons) and three vaccination studies (n = 10) were conducted in a commercial setting. The two included studies in the vaccination meta-analysis were both conducted at research facilities. The live Salmonella Typhimurium vaccine showed the most promise in reducing the prevalence of Salmonella in broiler ceca. However, the meta-analysis included few studies, and these studies challenged the birds with different serotypes. We recommend that more large-scale randomized, blinded trials be conducted with a live Salmonella Typhimurium vaccine on commercial farms.     

Fat contributes to the buffering capacity of chicken skin and meat but enhances the vulnerability of attached Salmonella cells to acetic acid treatment

Chicken skin and chicken meat display different buffering effects which may impact the survival of Salmonella attached to them when treated with acids. This study investigated the role that differences in fat composition of chicken skin and meat play in their buffering capacity. The survival of Salmonella attached to chicken skin and meat in the presence of fat, and treated with acetic acid was also investigated. Fat was extracted from chicken skin and meat and the buffering capacities of chicken skin, meat, extracted fat and their respective remnants were determined. Two strains of Salmonella Typhimurium and two strains of S. Enteritidis were attached independently to each of the chicken component listed above and enumerated before and after treatment with 0.3 M acetic acid. Chicken skin has a higher fat content as compared to chicken meat. Skin (13 mmol H⁺/(pH1 kg)) had a stronger buffering capacity (p < 0.05) than the extracted fat alone and skin remnants alone (7.0 mmol H⁺/(pH 1 kg) and 6.9 mmol H⁺/(pH 1 kg) respectively). From an initial inoculum (~ 9 log CFU/g), Salmonella cells attached better (p < 0.05) to chicken meat (~ 8 log CFU/g) and chicken skin (~ 7 log CFU/g) than extracted fat (~ 1.5 log CFU/g). Skin remnants without fat were better (p < 0.05) at protecting attached Salmonella than other chicken components. For example S. Typhimurium ATCC 33062 decreased ~ 1 log CFU/g (p < 0.05) on skin remnants after acetic acid treatment while its viable counts on other components decreased from ~ 1.5 to 7 log CFU/g (p < 0.05). We suggest that the fat content present in the skin may enhance the vulnerability of attached cells to acetic acid.     

Effect of reducing nitrate and nitrite added to dry fermented sausages on the survival of Salmonella Typhimurium

Salmonella is one of the pathogens that most frequently contaminate pork processing lines. Several hurdles can control this organism in dry fermented sausages, among them is nitrite. However, the traditional use of nitrate/nitrite in the meat industry is being questioned due to their involvement in nitrosamine formation. In this study, minced pork and sausages inoculated with Salmonella Typhimurium were prepared with 150 ppm NaNO₃ and 150 ppm NaNO₂ (maximum amounts allowed by EU), and with a reduction of 25% and 50%. The absence of nitrate/nitrite favored Salmonella growth, with 2–2.5 log cfu/g higher counts at the end of ripening, compared to nitrate/nitrite added batches. The 50% reduction showed the same inhibitory effect as the maximum amounts. Nitrate/nitrite represented an essential hurdle to control Salmonella even when pH and a_w were below the values considered as minimum for its growth. The effect of this reduction on other pathogens should be considered.     

Prevalence and antibiotic resistance of Salmonella serovars in ducks,duck rearing and processing environments in Penang,Malaysia

An investigation was carried out to determine the prevalence and antibiotic resistance of Salmonella serovars in ducks, their rearing and processing environments in Penang, Malaysia. A total of 531 samples collected from wet markets and duck farms, were examined from August 2009 to October 2010. The overall prevalence of Salmonella serovars was 23.5% (125/531). The 125 Salmonella isolates belong to 10 different serovars namely Typhimirium (29.6%), Enteritidis (12.0%), Gallinarum (2.4%), Braenderup (12.0%), Albany (11.2%), Hadar (20.8%), Derby (6.4%), Weltevreden (1.6%), Newbrunswick (3.4%) and London (0.8%). Salmonella serovars also showed various resistance patterns against 13 different antibiotics. All the serovars were resistant to erythromycin but susceptible to cephalothin, gentamicin and ceftriaxone. Plasmids were detected in 91 (72.8%) of the isolates with sizes ranging from 1.4 to 23.1 Kbp. Our findings provide baseline information on the distribution of Salmonella serovars in ducks, their rearing and processing environments, and indicate that ducks should be considered as an important source of food-borne pathogens.     

Changes in the antimicrobial resistance profiles of Salmonella isolated from the same Michigan dairy farms in 2000 and 2009

This study compared the antimicrobial resistance profiles of Salmonella collected from the same Michigan, USA dairy farms between the years 2000 and 2009. The specific objective was to understand the type and distribution of changes in antimicrobial resistance that occurred within farms over the past 10 years. Multinomial, multilevel models were constructed to estimate the differences in minimum inhibitory concentrations (MICs) between years. The MICs of most antimicrobials were significantly lower in 2009 than in 2000, but were higher for amikacin and gentamicin. Decreases in MICs were in part due to changes in the prevalence of multidrug resistant strains, but were also distributed across the susceptible population of isolates. The type and direction of within-farm changes in MICs were similar for the majority of farms. These results suggest a decrease in antimicrobial resistance and/or a change in the population structure of Salmonella that colonize dairy farms in Michigan.     

Salmonella contamination of laying-hen flocks in two regions of Algeria

A preliminary epidemiological study of Salmonella contamination in laying-hen flocks was carried out in the regions of Annaba and Eltarf, Algeria, from March to October 2008 and March to November 2009. Our objectives were (i) to estimate the prevalence of infection by Salmonella spp. in seven pooled samples during the hens' laying period (ii) to identify the serotypes and antimicrobial resistance phenotypes of isolates, and (iii) to characterize the factors that may be related to Salmonella contamination in Algerian henhouses. For this purpose, 18 out of 22 operational laying-hen houses were sampled one to three times during these periods: once at the start of laying (pullets aged 22–31 weeks), once in the middle of laying (47–60 week) and once at the end of laying prior to depopulation (70–86 week). The flocks'Salmonella status was assessed by collecting 2754 environmental samples that were analyzed according to the ISO 6579 method. The antibiotic resistance of Salmonella strains was tested as per the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The relationship between each potential risk factor and the Salmonella status of laying-hen flocks was evaluated by calculating the relative risk with 95% confidence intervals. Eight flocks tested positive for Salmonella spp., with a higher prevalence at the end of laying than at either the beginning or middle. Only 19 isolates were recovered from the 2754 samples analyzed and nine different serotypes identified. S. enteritidis (n = 4) was the most prevalent serovar, along with S. Kentucky and S. Hadar (n = 3), followed by S. Heidelberg, S. Manhattan and S. Virchow (n = 2), whereas S. Dublin, S. Typhimurium and S. Albany were found only once. Thirteen isolates were resistant to at least one antimicrobial agent. Of these, six were resistant to at least three different antimicrobial classes. Salmonella serovar Kentucky isolates were resistant to fluoroquinolones with ciprofloxacin MIC ≥ 8 mg/L. Six risk indicators were identified as potentially related to the Salmonella status of layer houses.     

Serodiversity and serological as well as cultural distribution of Salmonella on farms and in abattoirs in Lower Saxony, Germany

In this study fattening pigs were monitored on farms and in the abattoir for Salmonella prevalence. The samples with the highest prevalence at slaughter should be identified with special attention to the distribution of Salmonella serovars on farms in comparison to those in slaughtered pigs. Another aim was to monitor whether high serological antibody responses in pigs are in accordance with the specific Salmonella serovars in tissues. From 3418 farm faecal samples, 191 were Salmonella positive (5.58%), whereas from slaughtered pigs 330 out of 2494 analysed samples were Salmonella positive (13.2%) with the highest prevalence in the caecal content (124/499 = 24.9%). The chi-square test for homogeneity between the serovars found on farms and in the different types of samples at slaughter was in most cases negative (p < 0.05). Exceptions were the similar serovars found in samples taken from farm 1 and in the corresponding ileocaecal lymph nodes extracted at slaughter (p = 0.1188); in samples taken from farm 2 and the corresponding tonsils (p = 0.1479) and in samples taken from farm 3 and the corresponding caecal content (p = 0.3230) and ileocaecal lymph nodes (p = 0.1921), respectively. The frequency distribution in different samples was significantly different in most cases. Three exceptions, the distribution between tonsils and caecal content among antibody titre in meat juice (cut off 40) and cultural detection of Salmonella spp. in ileocaecal lymph nodes, as well as between meat juice samples (cut off 20) and caecal content did not differ significantly. The Kappa indices only showed signs of weak concordance according to positive test results (Kappa ≤ 0.4) between different sample types on an animal basis. Pigs harbouring S. Typhimurium 1,4,12:i:1,2; DT104L in tonsils or S. Typhimurium 1,4,12:i:1,2 DT 104B low in caecal content or ileocaecal lymph nodes had the highest optical densities in meat juice. Apart from the different Salmonella prevalences between farms and slaughterhouses and in most cases nonexisting concordance in Salmonella serovar distribution on farms and at slaughter, also in future farm intervention strategies to control Salmonella in the food chain are not dispensable. This is because once introduced into a slaughterhouse via swine the serovars seem to maintain the resident slaughterhouse flora and add to it.     

Genetic characterization of antimicrobial resistance in Salmonella enterica serovars isolated from dairy cattle in Wisconsin

Salmonella enterica is a pathogen of humans and animals, and is one of the most frequent causes of bacterial foodborne illness worldwide. People consuming contaminated foods or working with infected livestock have the potential to become infected with Salmonella and may require antimicrobial therapy. Antimicrobial resistance in Salmonella has become a problem worldwide due in part to the inappropriate use of antimicrobial agents in human and veterinary medicine. In this study, forty-five Salmonella isolates from diagnostic fecal samples of Wisconsin dairy cattle were serotyped and characterized by antimicrobial susceptibility testing using agar disk diffusion, antimicrobial resistance gene detection by PCR, plasmid analysis and conjugation studies. The predominant serovars detected were Kentucky, Newport, Typhimurium, Cerro, Dublin and Montevideo. Over half (51%) of all isolates were resistant to at least one antimicrobial agent, and 29% were resistant to 8–10 drugs. The most commonly observed resistance phenotypes were to streptomycin (44%), tetracycline (42%), sulfisoxazole (40%), chloramphenicol (35%), ampicillin (33%), and cefoxitin (33%). When resistance was detected phenotypically, a corresponding resistance gene was detected 86.2% of the time. Plasmids ranging in size from < 8 to 165 kb were detected in 45% of the isolates. A greater understanding of the factors associated with antimicrobial resistance in Salmonella should provide insights into the factors that contribute to the development of resistant pathogens during dairy production, which in turn can lead to strategies to minimize the spread of antimicrobial resistant Salmonella in the food supply.     

A survey of dry-salted natural casings for the presence of Salmonella spp., Listeria monocytogenes and sulphite-reducing Clostridium spores

A monitoring study was performed for the presence of Salmonella spp., Listeria monocytogenes and sulphite-reducing Clostridium spores in (internationally) traded dry-salted natural hog and sheep casings. Two hundred and fourteen consignments were examined for Salmonella spp. and L. monocytogenes, and 138 for the Clostridium spores.None of the 214 sampled consignments (25 g amounts investigated) yielded Salmonella spp., or L. monocytogenes.Differential reinforced clostridial medium was effective in detecting the presence of sulphite-reducing clostridia. Iron sulphite agar (ISA) overall showed higher clostridia counts as compared to differential reinforced clostridial agar (DRCA). The maximum spore counts obtained on DRCA and ISA were 17.5 and 2500 cfu g⁻¹, respectively. From the casings from China, 3 (of 35 hog consignments) and 7 (of 22 sheep) showed spore counts above 100 cfu g⁻¹. From the remaining 81 samples, originating from Netherlands, New Zealand and UK, none showed a count above 100 cfu g⁻¹.The relevance of the presence of sulphite-reducing Clostridium spores for the manufacture of various meat products is discussed. It is recommended that determination of the Clostridium strains present is carried out and their properties investigated in relation to the manufacture of meat products, since some of the strains may be potentially pathogenic and/or able to spoil products.     

Dynamics of endemic infectious diseases of animal and human importance on three dairy herds in the northeastern United States

Endemic infectious diseases in dairy cattle are of significant concern to the industry as well as for public health because of their potential impact on animal and human health, milk and meat production, food safety, and economics. We sought to provide insight into the dynamics of important endemic infectious diseases in 3 northeastern US dairy herds. Fecal samples from individual cows and various environmental samples from these farms were tested for the presence of major zoonotic pathogens (i.e., Salmonella, Campylobacter, and Listeria) as well as commensal bacteria Escherichia coli and enterococci. Additionally, the presence of Mycobacterium avium ssp. paratuberculosis was tested in fecal and serum samples from individual cows. Test results and health and reproductive records were maintained in a database, and fecal, plasma, DNA, and tissue samples were kept in a biobank. All bacteria of interest were detected on these farms and their presence was variable both within and between farms. The prevalence of Listeria spp. and L. monocytogenes in individual fecal samples within farm A ranged from 0 to 68.2% and 0 to 25.5%, respectively, over a period of 3 yr. Within farm B, continuous fecal shedding of Salmonella spp. was observed with a prevalence ranging from 8 to 88%; Salmonella Cerro was the predominant serotype. Farm C appeared less contaminated with Salmonella and Listeria, although in the summer of 2005, 50 and 19.2% of fecal samples were positive for Listeria and L. monocytogenes, respectively. The high prevalence of E. coli (89 to 100%), Enterococcus (75 to 100%), and Campylobacter (0 to 81%) in feces suggested they were ubiquitous throughout the farm environment. Fecal culture and ELISA results indicated a low prevalence of Mycobacterium avium ssp. paratuberculosis infection in these farms (0 to 13.6% and 0 to 4.9% for culture-positive and ELISA-positive, respectively), although the occasional presence of high shedders was observed. Results have major implications for food safety and epidemiology by providing a better understanding of infectious disease dynamics on dairy farms. Comprehensive understanding of these infections may lead to better farm management practices and pathogen reduction programs to control and reduce the on-farm contamination of these pathogens and to prevent their further entry into the food-chain.     

Investigation of Salmonella enterica in Sardinian slaughter pigs: prevalence, serotype and genotype characterization

In order to improve the knowledge about the presence of Salmonella in pork meat in Sardinia (Italy), the prevalence and the sources of Salmonella at 5 pig slaughterhouses (slaughtered pigs and environment) were investigated and the isolates were characterised. A total of 462 samples were collected, 425 from pigs at slaughter and 41 from the slaughterhouse environment. Salmonella was isolated from 26/85 (30.5%) mesenteric lymph nodes, 14/85 (16.4%) colon contents, and from 12/85 (14.1%) carcasses and livers. Salmonella prevalence was 38% (8/21) in samples from surfaces not in contact with meat, and 35% (7/20) in those from surfaces in contact with meat. Thirty-one pigs were identified as carriers of Salmonella in lymph nodes and/or colon content, but of these, only 8 carcasses were positive. A total of 103 Salmonella isolates were serotyped and genotyped. Eight different serotypes were detected; the most common were S. Derby (44/103, 42.7%) and S. Typhimurium (24/103, 23.3%). The most prevalent S. Typhimurium phage type was DT193. Thirty-two isolates were found to be resistant to more than one antimicrobial (MDR). Pulse-field gel electrophoresis (PFGE) permitted the resolution of XbaI macrorestriction fragments of the Salmonella strains into 20 distinct pulsotypes. Combined application of a plasmid profiling assay (PPA) and PFGE gave useful additional information to assist in tracing the routes of Salmonella contamination in abattoirs. To reduce Salmonella prevalence some preventive measures should be encouraged: the origin of infected slaughter animals should be identified and direct and cross-contamination of carcasses should be avoided by adhering to HACCP principles in association with good hygiene procedures (GHP).     

Effects of cooked temperature on pork tenderness and relationships among muscle physiology and pork quality traits in loins from Landrace and Berkshire swine

The effect of, and associations between, loin muscle morphology and pork quality indicator traits were assessed at three cooked temperatures in loin chops from 38 purebred Berkshire and 52 purebred Landrace swine. Three loin chops from each pig were randomly assigned to cooked temperature treatments of 62, 71, or 79 °C and loin tenderness was assessed as Warner–Bratzler shear force (WBSF). Cooked temperature (P < 0.001), breed (P < 0.001) and breed × cooked temperature (P < 0.001) effects influenced loin chop WBSF, whereby WBSF increased as cooked temperature increased. Chops from Landrace pigs had greater WBSF at each cooked temperature compared with chops from Berkshire pigs. Chops from Landrace pigs became less tender with increasing cooked temperature, whereas chops from Berkshire pigs became less tender only when cooked to 79 °C. In loins from Landrace pigs, Minolta a1 at 62 °C (R² = 0.07), and average muscle fiber diameter at 71 °C and 79 °C (R² = 0.07 and 0.24, respectively), contributed to WBSF variation. In contrast, for loins from Berkshire pigs, loin ultimate pH and intramuscular fat percentage accounted for 27% and 30% of the variation in WBSF at 62 °C and 71 °C, respectively, and loin ultimate pH accounted for 7% of variation in WBSF at 79 °C. Results suggest that loins from Berkshire pigs have properties that resist toughening at greater cooked temperatures and that associations between quality measures and loin tenderness differ between Landrace and Berkshire pigs.     

Salmonella, Escherichia coli O157:H7 and E. coli biotype 1 in a pilot survey of imported and New Zealand pig meats

A pilot survey for the pathogens Salmonella and Escherichia coli O157:H7, and E. coli biotype 1 was conducted on 100 New Zealand-produced (domestic) pig carcasses and 110 imported pig meat samples over an 8-month period to assess the likelihood of introduction of novel pathogen strains into New Zealand (NZ), and as a guide for development of a domestic pork National Microbiological Database programme. Salmonella was not isolated from domestic pig carcasses or from pig meat imported from Canada and the USA. The prevalence of Salmonella in imported pig meat was 3.6% (95% CI 1.0–9.0) with positive samples detected from Australian pig meat. The prevalence of E. coli O157:H7 on domestic pig carcasses was 1% (95% CI 0.03–5.4) while the overall prevalence of E. coli O157:H7 in imported pig meat was 1.8% (95% CI 0.2–6.4), detected mainly from Australian but not from Canadian or US pork. All except three samples have an E. coli biotype 1 count of <100 CFU cm⁻² or g⁻¹, indicating good hygiene quality of domestic and imported pig meat. The results demonstrated that importation of uncooked pig meat is a potential route for the introduction of new clones of Salmonella and E. coli O157:H7 into New Zealand.