Carcass Swabs Research Articles

The proficiency testing program of the European Union Reference Laboratory for E. coli

Since 2006, the European Union Reference Laboratory for E. coli (EU-RL) has developed and evaluated standard operating procedures for the identification and typing of verocytotoxin-producing Escherichia coli (VTEC) and for their detection in food, mainly based on PCR detection of virulence genes. In particular, the EU-RL coordinated the development of the Technical Specification ISO TS 13136:2012 on the detection of VTEC in food and animal feed, based on the real-time PCR screening of food enrichment cultures. A total of 13 proficiency testing (PT) rounds were organized: 7 PTs on the identification and typing of VTEC and other pathogenic E. coli strains (detection of virulence genes by PCR and identification of the VTEC serogroups by serological and molecular methods) and 6 PTs on the detection of VTEC in different matrices (carcass swabs, milk, spinach, water, seeds and sprouts), analyzed by using the ISO TS 13136 method. A Web-based platform for submitting the PT results was developed and used since 2010. Between 2007 and 2014, a positive trend was observed in both the number of participants and their performance. Through its PT program, the EU-RL has consolidated a network of reference laboratories for the control of pathogenic E. coli in the EU Member States. Such a network can contribute to gather harmonized data on the prevalence of VTEC in food, to improve the knowledge of the epidemiology of VTEC infections in Europe, and to provide the EC with more standardized operative structures and tools to face possible emergencies in this field of food safety.

Genotypic Characterization of <i>Shigella</i> Species Isolated from Abattoirs in the North West Province, South Africa Using PCR Analysis

Foodborne pathogens pose a serious threat to food safety especially in developing countries where hygiene facilities are not well developed and operational practices in abattoirs and retail shops are often poor. Shigella species are known to cause foodborne complications in humans including shigellosis that is not only characterized by destruction of the epithelium of the colon but usually results to an inflammatory response. The transmission of Shigella species to humans most often results through the consumption of contaminated food, meat and water. The aim of this study was to isolate and identify Shigella species from carcass of cattle in some abattoirs in the North West Province, South Africa and determine the virulence gene profiles of the isolates using PCR assays. A total of 97 carcass swabs were obtained from the abattoirs that were sampled. Swabs were properly labeled and transported on ice to the laboratory for analysis. The swabs were washed in 2% (w/v) peptone water and plated on Salmonella-Shigella agar. Standard identification tests (Gram staining, oxidase test, TSI test and 16S rRNA) were used to confirm the identities of 97 (one from each sample) presumptive isolates. Large proportions (85% to 100%) of the isolates from Rustenburg and Zeerust were oxidase positive. None of the isolates produced hydrogen sulphide gas on TSI medium but utilize glucose as a source of carbon. A large proportion (75.3%) of the isolates was positively identified as Shigella species based on PCR analysis. The number of isolates confirmed as Shigella species was higher in Zeerust (54.8%) than in Rustenburg (45.2%). Shigella species were most often isolated from samples that were collected outside than inside the carcass. Generally a large proportion (74.0%) of the isolates possessed the IpaH gene while64.4% of these isolates were positive for the IpaBCD gene that encodes for the invasion plasmid antigen. An analysis of the isolates from the different sampling sections indicated that 46.3% and 55.3% of the isolates from Zeerust possessed the IpaH and the IpaBCD genes, respectively while 53.7% and 44.7% of the isolates from Rustenburg possessed these genes. The detection of virulent Shigella species in beef carcasses demonstrates the need for a continued surveillance of this pathogen in meat in order to ensure the implementation of improved food safety measures.

English

A cross-sectional study was conducted from January to April 2014 on 249 apparently healthy slaughtered goats at the municipal abattoir of Dire Dawa to estimate the prevalence Salmonella spp. and determine the antimicrobial susceptibility pattern of the isolates. A total of 249 goat carcass swab samples were collected using a systematic random sampling technique and examined for the presence of Salmonella spp. Out of the total of 249 carcass swab samples, 44 (17.7%) were positive for Salmonella. Of all the isolates, 41 (93.2%) were multiply antimicrobial resistant and the highest level of resistance was observed for tetracycline (100%), nitrofurans (100%), streptomycin (81.8%) and kanamycin (79.5%). However, all isolates were susceptible to ciprofloxacin. The present study shows high prevalence of Salmonella spp. contamination of goat meat and resistance of the pathogen to most antimicrobials except ciprofloxacin. Authors recommended the use of standardized procedures and applications in handling of goat meat in the abattoir and rational use of antimicrobials particularly ciprofloxacin. Furthermore studies should be conducted to identify the potential source of contamination and identification of genes responsible for antimicrobial resistance.   Key words: Abattoir, antimicrobial sensitivity, goat meat, prevalence, Salmonella.&nbsp

Prevalence and risk factors associated with Clostridium difficile shedding in veal calves in Italy

The aim of this study is to describe the prevalence and risk factors of Clostridium difficile shedding in six farms belonging to two companies in Northern Italy. Four hundred and twenty veal calves, randomly selected and individually identified, were sampled three times: at 0–16, 90–120, and 150 days after introduction. C. difficile was isolated at least once from 87 out of the 420 calves (20.7%). The prevalence of shedding was 20.24% at the first sampling and dropped to 0.72% at the second sampling. None of the samples obtained at 150 days tested positive. Sampling of cecal contents and carcass swabs at slaughter was stratified according to the herd of origin of the animals. C. difficile was never isolated at slaughter, excluding a prevalence higher than 3.5% on the basis of previous investigations. Therefore, in this work, the veal calf could not be confirmed as a potential source of C. difficile for the consumer. Eight different ribotypes (RT) have been described, but the vast majority of the isolates (87.8%) belonged to three ribotypes only: RT-078, RT-012 and RT-126, which are also among the most common of the ribotypes detected in humans in Europe. Most isolates, and all the RT-078 isolates, harbored genes coding for toxins A and B, the binary toxin, and showed a deletion in the gene encoding toxin C, suggesting that the veal calf was a reservoir for epidemic hyper-virulent strains. A correlation between age and shedding was found: the odds ratio (OR) ranged from 2.79 for 36–45 days of age to 4.57 for 13–28 days of age. The presence of diarrhea at first sampling was significantly associated with the recovery of C. difficile in feces (OR 3.26). A correlation was found between the administration of antimicrobials and shedding: an increased risk was shown when the number of antimicrobials used was higher than 4 (OR 4.02) or 5–6 (OR 5.83) or when polymyxin E or beta-lactams were administered.

Prevalence and Characterization of Salmonella Isolated from Beef in Namibia

Aim: The purpose of this research was to determine the prevalence of Salmonella in raw beef produced from selected commercial abbatoirs in Namibia. Methodology: A total of 9508 of beef samples from three different types of samples; meat cuts, carcass swabs and meat fluid were collected from the three local abattoirs over a period of two years starting from January 2008 to December 2009. Pre - enrichment for isolati on of Salmonella was done in Buffered peptone water followed by enrichment in the Rappaport - Vassiliadis and selenite cystine broth. The isolation of Salmonella was done on Xylose Lysine Desoxycholate and Brilliant Green agar followed by biochemical confirm ation and serotyping according to Kauffman White scheme. Results: The overall prevalence of Salmonella was 0.85 % for beef samples derived from meat cuts, meat fluid and carcass swabs. The prevalence of Salmonella in carcass swabs (2.67 %) was significantly different ( P = 0.0 5) from that of meat cuts (0.50 % ) and meat fluid (0.43 %). No significant difference ( P = 0.05) on the prevalence of Salmonella existed between the meat cuts and meat fluid. A total of 34 different types of Salmonella serovars were identified with S. Chester being the most frequently isolated serovars (n = 12), followed by S. Reading and S . Bredeney (n = 6) and S. Typhimurium (n = 5). Conclusions: The prevalence of Salmonella in raw beef found in this survey was lower than those observed in Sub Sahara Africa with S. Chester being the most prevalent serovar. Original Research Article

Fast and discriminative CoSYPS detection system of viable Salmonella spp. and Listeria spp. in carcass swab samples

In this study, the complete CoSYPS Path Food workflow including all steps, namely swab sample enrichment, SYBR®Green qPCR detection of Salmonella spp. and Listeria spp., isolation and confirmation of the detected strain, was validated on beef carcass swabs. To perform the validation, the results of the complete workflow were compared, according to the ISO 16140:2003, with the ISO reference methods for detection, isolation and confirmation of Listeria monocytogenes and Salmonella spp. The results showed that the relative level of detection and the limit of detection of the complete workflow and ISO reference methods are in a range from 2 to 16CFU/swab for both bacteria. The relative specificity, sensitivity and accuracy identified during this validation were all 100% since the results obtained with the complete CoSYPS Path Food workflow and the ISO reference methods were identical (Cohen's kappa index=1.00). In addition the complete CoSYPS Path Food workflow is able to provide detection results (negative or presumptive positive) in half the time needed as for the ISO reference methods. These results demonstrate that the performance of the complete CoSYPS Path Food workflow is not only comparable to the ISO reference methods but also provides a faster response for the verification of beef carcasses before commercial distribution.

Abattoir based survey of Salmonella in finishing pigs in the United Kingdom 2006–2007

All European Union (EU) Member States (MSs) were required to conduct a baseline survey from October 2006 to September 2007 to estimate the prevalence of Salmonella infection in finisher pigs at slaughter. In the United Kingdom (UK), samples for microbiological culture were collected from the ileo-caecal lymph nodes, from carcass swabs and from caecal contents. Meat juice samples were also collected for testing in an enzyme-linked immunosorbent assay (MJE) to detect a serological response. Salmonella was isolated from 22% (CI95% 19–25%) of ileo-caecal lymph nodes, 15% (CI95% 12–18%) of carcass swabs and 22% (CI95% 19–26%) of caecal contents. A quarter (25%, CI95% 22–29%) of MJE samples were positive for Salmonella antibodies (cut-off, S/P≥0.25). The most frequently identified serovars were Salmonella typhimurium (57%) and Salmonella derby (26%). The results were used to investigate some factors associated with Salmonella infection in slaughter pigs. The weight of the carcass was significant, with a lower probability of obtaining a positive meat juice result from pigs with a weight greater than 75kg (p=0.03). The weight of the lymph node sample was significantly associated with Salmonella status, with a heavier sample of lymph nodes being more likely to be positive (OR=2.16 CI95% 1.07–4.39). ‘Carcass weight’ in two of the classes – 75–79kg and 80–84kg – (OR=0.44 CI95% 0.28–0.70; OR=0.64 CI95% 0.49–0.85) and ‘fewer-than-1500-pigs’ scheduled for slaughter on the day of sampling’ (OR=0.41 CI95% 0.24–0.71) were also associated with a reduced risk of isolating Salmonella from lymph node. The model for carcass swabs showed a positive association with ‘time-elapsed-since-the-start-of-the-line’ indicating a higher risk of contamination as the day progressed (p<0.01). This model also showed positive association between isolation of Salmonella from a carcass swab and the occurrence of Salmonella in caecal contents from the same pig (OR=2.22 CI95% 1.38–3.59) and a negative association with time in singeing units (OR=0.88 CI95% 0.79–0.98).

Preslaughter diet management in sheep and goats: effects on physiological responses and microbial loads on skin and carcass

Sixteen crossbred buck goats (Kiko x Spanish; BW = 32.8 kg) and wether sheep (Dorset x Suffolk; BW = 39.9 kg) were used to determine the effect of preslaughter diet and feed deprivation time (FDT) on physiological responses and microbial loads on skin and carcasses. Experimental animals were fed either a concentrate (CD) or a hay diet (HD) for 4 d and then deprived of feed for either 12-h or 24-h before slaughter. Blood samples were collected for plasma cortisol and blood metabolite analyses. Longisimus muscle (LM) pH was measured. Skin and carcass swabs were obtained to assess microbial loads. Plasma creatine kinase activity (863.9 and 571.7 ± 95.21 IU) and non-esterified fatty acid concentrations (1,056.1 and 589.8 ± 105.01 mEq/L) were different (P < 0.05) between sheep and goats. Species and diet treatments had significant effects on the ultimate pH of LM. Pre-holding total coliform (TCC) and aerobic plate counts (APC) of skin were significantly different between species. Goats had lower (P < 0.05) TCC (2.1 vs. 3.0 log10 CFU/cm2) and APC (8.2 vs. 8.5 log10 CFU/cm2) counts in the skin compared to sheep. Preslaughter skin E. coli counts and TCC were different (P < 0.05) between species. Goats had lower (P < 0.05) counts of E. coli (2.2 vs. 2.9 log10 CFU/cm2) and TCC (2.3 vs. 3.0 log10 CFU/cm2) in the skin compared with those in sheep. Diet, species, and FDT had no effect (P > 0.05) on E. coli and TCC in carcass swab samples. The APC of carcass swab samples were only affected (P < 0.05) by the FDT. The results indicated that preslaughter dietary management had no significant changes on hormone and blood metabolite concentrations and sheep might be more prone for fecal contamination than goats in the holding pens at abattoir.

Detection of genes encoding for virulence and adherence factors in Escherichia coli isolated in slaughtered Sarda breed sheep

In order to investigate the pathogenic profile of Escherichia coli hosted in “Sarda” sheep, autochthonous race present in Sardinia, thirty-seven E. coli strains collected from different sources (fleeces, carcass swabs and gut mucosa) of pre-chill slaughtered sheep (ewes and lambs) were serotyped using pheno- and genotypic methods. Furthermore, the presence of genes encoding for virulence factors and mediating for localized mucosal adherence factors was investigated, and pulsed-field gel electrophoresis (PFGE) characterization was performed.Twenty-one (56.8%) of the isolates belonged to O91 serogroup and sixteen (43.2%) belonged to nine different serotypes (O5:H11, O8:H14, O26:H2, O38:H26, O116:H9, O116:H11, O132:H34, O149:H?, O161:H-). Of these non-O91 strains, five (13.5%) were able to produce verocytotoxin (VT) and were ascribed to VTEC pathogroup, eleven (29.7%) were attributed to the Enteropathogenic E. coli (EPEC) pathogroup; the other strains (n.21) cannot be ascribed to a pathogenic group. However, various associated virulence genes were observed in all isolated strains. Macrorestriction analysis highlighted a large heterogeneity of the E. coli strains.The results confirm the role of sheep as reservoir of pathogenic E. coli serotypes potentially able to colonize and to damage the intestinal mucosa.

Conducting inferential statistics for low microbial counts in foods using the Poisson-gamma regression

Mixed Poisson distributions have been shown to be able to represent low microbial counts more efficiently than the lognormal distribution because of its greater flexibility to model microbial clustering even when data consist of a large proportion of zero counts. The objective of this study was to develop an alternative modelling framework for low microbial counts based on heterogeneous Poisson regressions. As an illustration, Poisson-gamma regression models were used to assess the effect of chilling on the concentration of total coliforms from beef carcasses (n = 600) sampled at eight large Irish abattoirs. Three Poisson-gamma and three zero-modified (hurdle and zero-inflated) models were appraised with a series of random-effects variants in order to extract any variability in microbial mean concentration, dispersion and/or proportion of zero counts. Models were compared and validated in their ability to predict the coliforms counts on carcasses after chilling. In all five test batches, the hurdle Poisson-gamma distributions predicted the observed post-chill counts closer than the Poisson-gamma distributions. This is justified by the better capacity of the hurdle model to represent a higher proportion of zero counts, which were in fact observed in the post-chill batches. Thus, with a coded variable (pre-chill/post-chill) as treatment, and extracting the significant variability of batches nested in abattoirs for the coliforms mean concentration (σ2u = 2.68), the dispersion measure (σ2v = 2.39) and the probability of zero counts (σ2w = 0.89), the validated hurdle Poisson-gamma model confirmed that chilling has a decreasing effect on the viability of coliforms from beef carcasses, and that the concentration is reduced by an average (pre-chill to post-chill) factor of 2.2 (95% CI: 2.15–2.24) at batch level. The model also indicated that chilling increases the odds of producing a zero count from a carcass swab in about 13.5 times, and that the higher the coliforms concentration in a batch, the weaker the effect that chilling has to reduce such contamination on the beef carcasses.

Prediction of Salmonella carcass contamination by a comparative quantitative analysis of E. coli and Salmonella during pig slaughter

Faecal contamination of carcasses in the slaughterhouse is generally considered to be the source of Salmonella on pork. In this study the hygiene indicator Escherichia coli is used to quantify faecal contamination of carcasses and it is hypothesized that it can be used to predict the quantitative carcass contamination with Salmonella, when the distribution of Salmonella concentrations in faeces is known. Paired pig sample data (faecal samples and carcass swabs) were obtained from five slaughterhouses and analysed for prevalence and concentrations of E. coli and Salmonella. A simple model was developed to describe the faecal contamination of carcasses using the E. coli data. The E. coli results suggested different hygiene performances in different slaughterhouses, and showed that a model assuming that carcasses are predominantly contaminated by their own faeces was not appropriate. Observed Salmonella prevalences were low (on average 1.9% on carcasses) and between slaughterhouses the prevalences ranked differently than the hygiene performance based on the E. coli data suggested. Also, the Salmonella concentrations predicted using E. coli as a faecal indicator were lower than the observed Salmonella concentrations. It is concluded that the faecal carriage of Salmonella together with the faecal contamination of carcasses, as predicted from E. coli data in the animal faeces and hygiene performance of the slaughterhouse, is not sufficient to explain carcass contamination with Salmonella. Our extensive data set showed that other factors than the observed faecal carriage of Salmonella by the individual animals brought to slaughter, play a more important role in the Salmonella carcass contamination of pork.

Exploring the Sources of Bacterial Spoilers in Beefsteaks by Culture-Independent High-Throughput Sequencing

Microbial growth on meat to unacceptable levels contributes significantly to change meat structure, color and flavor and to cause meat spoilage. The types of microorganisms initially present in meat depend on several factors and multiple sources of contamination can be identified. The aims of this study were to evaluate the microbial diversity in beefsteaks before and after aerobic storage at 4°C and to investigate the sources of microbial contamination by examining the microbiota of carcasses wherefrom the steaks originated and of the processing environment where the beef was handled. Carcass, environmental (processing plant) and meat samples were analyzed by culture-independent high-throughput sequencing of 16S rRNA gene amplicons. The microbiota of carcass swabs was very complex, including more than 600 operational taxonomic units (OTUs) belonging to 15 different phyla. A significant association was found between beef microbiota and specific beef cuts (P<0.01) indicating that different cuts of the same carcass can influence the microbial contamination of beef. Despite the initially high complexity of the carcass microbiota, the steaks after aerobic storage at 4°C showed a dramatic decrease in microbial complexity. Pseudomonas sp. and Brochothrix thermosphacta were the main contaminants, and Acinetobacter, Psychrobacter and Enterobacteriaceae were also found. Comparing the relative abundance of OTUs in the different samples it was shown that abundant OTUs in beefsteaks after storage occurred in the corresponding carcass. However, the abundance of these same OTUs clearly increased in environmental samples taken in the processing plant suggesting that spoilage-associated microbial species originate from carcasses, they are carried to the processing environment where the meat is handled and there they become a resident microbiota. Such microbiota is then further spread on meat when it is handled and it represents the starting microbial association wherefrom the most efficiently growing microbial species take over during storage and can cause spoilage.

Antimicrobial activity of three wines against Campylobacter jejuni and the effect of low temperature on their survival ability

Forty-three (43) Campylobacter jejuni isolated from sheep feces and carcass swab samples by conventional culture method were 100% confirmed by polymerase chain reaction (PCR) test. The nucleotide sequences of 362 bp showed 100% homology to the completed genome of C. jejuni subsp. M1 and 81116. Antimicrobial property of different types of wine against C. jejuni was investigated. White wine and two red wines with 11.5% ethanol significantly reduced the viability of C. jejuni. The minimum bactericidal concentration of white wine and for both red wines was 10 and 25%, respectively. C. jejunilost their viability when frozen or refrigerated at -20 and 4°C. The reduction rates of C. jejuni were 0.54 - 1.02 logCFU/ml during storage at 4°C, whereas it exhibited 0.72 - 1.52 logCFU/ml during storage at -20°C. Key words: Conventional culture, polymerase chain reaction (PCR), viability.

Longitudinal Study of Distributions of Similar Antimicrobial-Resistant Salmonella Serovars in Pigs and Their Environment in Two Distinct Swine Production Systems

The aim of this longitudinal study was to determine and compare the prevalences and genotypic profiles of antimicrobial-resistant (AR) Salmonella isolates from pigs reared in antimicrobial-free (ABF) and conventional production systems at farm, at slaughter, and in their environment. We collected 2,889 pig fecal and 2,122 environmental (feed, water, soil, lagoon, truck, and floor swabs) samples from 10 conventional and eight ABF longitudinal cohorts at different stages of production (farrowing, nursery, finishing) and slaughter (postevisceration, postchill, and mesenteric lymph nodes [MLN]). In addition, we collected 1,363 carcass swabs and 205 lairage and truck samples at slaughter. A total of 1,090 Salmonella isolates were recovered from the samples; these were isolated with a significantly higher prevalence in conventionally reared pigs (4.0%; n = 66) and their environment (11.7%; n = 156) than in ABF pigs (0.2%; n = 2) and their environment (0.6%; n = 5) (P < 0.001). Salmonella was isolated from all stages at slaughter, including the postchill step, in the two production systems. Salmonella prevalence was significantly higher in MLN extracted from conventional carcasses than those extracted from ABF carcasses (P < 0.001). We identified a total of 24 different serotypes, with Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Anatum, Salmonella enterica serovar Infantis, and Salmonella enterica serovar Derby being predominant. The highest frequencies of antimicrobial resistance (AR) were exhibited to tetracycline (71%), sulfisoxazole (42%), and streptomycin (17%). Multidrug resistance (resistance to ≥ 3 antimicrobials; MDR) was detected in 27% (n = 254) of the Salmonella isolates from the conventional system. Our study reports a low prevalence of Salmonella in both production systems in pigs on farms, while a higher prevalence was detected among the carcasses at slaughter. The dynamics of Salmonella prevalence in pigs and carcasses were reciprocated in the farm and slaughter environment, clearly indicating an exchange of this pathogen between the pigs and their surroundings. Furthermore, the phenotypic and genotypic fingerprint profile results underscore the potential role played by environmental factors in dissemination of AR Salmonella to pigs.

Presence of Shiga Toxin–ProducingEscherichia coliO-Groups in Small and Very-Small Beef-Processing Plants and Resulting Ground Beef Detected by a Multiplex Polymerase Chain Reaction Assay

Shiga toxin-producing Escherichia coli (STEC) are associated with foodborne illnesses, including hemolytic uremic syndrome in humans. Cattle and consequently, beef products are considered a major source of STEC. E. coli O157:H7 has been regulated as an adulterant in ground beef since 1996. The United States Department of Agriculture Food Safety and Inspection Service began regulating six additional STEC (O145, O121, O111, O103, O45, and O26) as adulterants in beef trim and raw ground beef in June 2012. Little is known about the presence of STEC in small and very-small beef-processing plants. Therefore, we propose to determine whether small and very-small beef-processing plants are a potential source of non-O157:H7 STEC. Environmental swabs, carcass swabs, hide swabs, and ground beef from eight small and very-small beef-processing plants were obtained from October 2010 to December 2011. A multiplex polymerase chain reaction assay was used to determine the presence of STEC O-groups: O157, O145, O121, O113, O111, O103, O45, and O26 in the samples. Results demonstrated that 56.6% (154/272) of the environmental samples, 35.0% (71/203) of the carcass samples, 85.2% (23/27) of the hide samples, and 17.0% (20/118) of the ground beef samples tested positive for one or more of the serogroups. However, only 7.4% (20/272) of the environmental samples, 4.4% (9/203) of the carcass samples, and 0% (0/118) ground beef samples tested positive for both the serogroup and Shiga toxin genes. Based on this survey, small and very-small beef processors may be a source of non-O157:H7 STEC. The information from this study may be of interest to regulatory officials, researchers, public health personnel, and the beef industry that are interested in the presence of these pathogens in the beef supply.

Pathogenic Microbiological Baseline Survey of Pork Carcasses in Taiwan

From 2004 to 2010, pork carcass swabs from state-inspected slaughter plants in Taiwan were intermittently analyzed to determine the prevalence of selected pathogenic microorganisms associated with foodborne illness. The prevalences of Staphylococcus aureus each year from 2006 to 2010 were 6.6, 10.8, 5.1, 6.4, and 7.4%, respectively, while those of Listeria monocytogenes were 1.2% in 2004, 1.3% in 2005, and 3.5% in 2008. The prevalences of Clostridium perfringens were 0.9% in 2004, 3.2% in 2005, and 1.1% in 2008. Campylobacter jejuni and Campylobacter coli had a higher recovery rate than the other surveyed microorganisms, with prevalences during 2004, 2005, and 2008 of 21.1, 13.7, and 8.1%, respectively. Salmonella strains were analyzed each year, and their prevalences ranged between 3.0 and 6.9%. Derby, Typhimurium, Anatum, Choleraesuis, and Agona were the five serovars most frequently identified among the Salmonella isolates. Escherichia coli O157:H7 was not detected in 2004, 2005, or 2010. Routine baseline surveying of pork carcasses to determine the prevalence of selected pathogens of concern for food safety can provide valuable information regarding the effectiveness of the slaughtering procedures or the need for interventions.

Evaluation of the ISO 10273:2003 method for the isolation of human pathogenic Yersinia enterocolitica from pig carcasses and minced meat

Pig carcass swabs (n = 254) and minced meat samples (n = 82) were examined for pathogenic Yersinia enterocolitica using different routinely used enrichment protocols. All samples were obtained in the context of the official Yersinia monitoring program in Belgium. In total, 28 carcasses (11.0%) were contaminated with Y. enterocolitica bioserotype 4/O:3 and one (0.4%) with bioserotype 2/O:9. Four minced meat samples (4.9%) tested positive for Y. enterocolitica bioserotype 4/O:3. Using the ISO 10273:2003 method, eight out of the 29 Yersinia-positive carcasses (27.6%) and none of the contaminated minced meat samples (0.0%) were detected. Reducing the enrichment time in PSB from 5 to 2 days increased the number of positive samples. Overall, enrichment in PSB at 25 °C recovered more positive carcasses and minced meat samples than selective enrichment and cold enrichment. As the exclusive use of the ISO 10273:2003 method results in a strong underestimation of Y. enterocolitica positive carcasses and minced meats, efforts are needed to optimize the current version of the ISO method. In addition, isolation of pathogenic Y. enterocolitica requires experience and the use of a stereomicroscope to avoid false negative results.

A small study of Yersinia enterocolitica in pigs from birth to carcass and characterisation of porcine and human strains

The objectives of this study were to investigate the present of Yersinia enterocolitica at the different stages of production from birth to chilled carcasses; to characterise the isolates in terms of bioserotype, virulence factors (ail, ystA, ystB, inv, yadA and virF) and antibiotic resistance profiles and to examine strains causing diarrheal illness in Ireland. Rectal, throat, floor, partition, wall and/or carcass swabs and water samples were testing for Y. enterocolitica using the bacteriological analytical method. Presumptive positive isolates were confirmed using API 20E strips. The isolates were then combined with 10 clinical strains, biotyped, serotyped, their antibiotic resistance phenotypes determined by disc diffusion and tested for the presence of ail, ystA, ystB, inv, yadA and virF genes using multiplex PCR assays. Y. enterocolitica had an overall prevalence rate of 0.55% (4/726). Y. enterocolitica 2/O:9 and 1A/O:9 were detected on the farm and/or in the abattoir. The clinical isolates were 1A/O:5, 1A/O:8, 1A/O:9, 2/O:9 or 4/O:9. All biotype 1A strains were ail, ystA, yadA and virF negative but carried the ystB gene. All biotype 2 and 4 strains were ail, ystA, yadA and virF positive. Resistant to cephalothin, ampicillin and amoxicillin/clavulanic acid was common and one 2/O:9 strain was resistant to compound sulphonamides and tetracycline. Intermediate resistance to neomycin and streptomycin was also observed. The data presented may explain the low incidence of yersiniosis in Ireland and suggests that biotype 1A may present a public health risk. Neomycin and tetracycline resistance have rarely been reported in Y. enterocolitica and should be monitored in future surveillance studies.

Influence of isolation methods on the occurrence of plasmid-carrying Yersinia enterocolitica serotype O:3 in slaughter pig tonsils, faeces and carcass surface swabs

Yersinia enterocolitica is an important foodborne pathogen that is primarily transmitted to humans through the consumption of contaminated pork. Different matrices of pigs at slaughter were tested for the presence of human pathogenic types of Y. enterocolitica using direct plating, selective enrichment, and cold enrichment. Y. enterocolitica serotype O:3 was isolated from the tonsils and faeces of 55.3% and 25.6% of pigs, respectively. The pathogen was also recovered from 15.0% of swab samples taken from the carcass surface post-evisceration. Tonsils positive by direct plating revealed an average concentration of 3.99 log10Y. enterocolitica per gram, whereas the majority of positive faecal and carcass samples were contaminated below the detection limit of enumeration. The relative sensitivity of the methods to recover pathogenic Y. enterocolitica varied among the different matrices. Nevertheless, cold enrichment was significantly more efficient than direct plating and selective enrichment for all three sample matrices. From the 2082 recovered Y. enterocolitica isolates, 1742 (83.7%) harboured the virulence plasmid. Isolates obtained from faeces were more likely to contain the virulence plasmid than isolates from tonsils and carcass swabs. To obtain reliable results regarding the presence of plasmid-carrying Y. enterocolitica isolates, sensitive isolation methods should be combined with testing of a sufficient number of isolates.

Prevalence, characterization and antimicrobial susceptibility of Salmonella enterica and Yersinia enterocolitica in pigs at slaughter in Italy

In 2005–2008, 1152 samples (451 faecal samples, 451 carcass swabs and 250 tonsils) were collected from 451 finishing pigs slaughtered in three abattoirs of northern Italy. In two abattoirs, 34 scalding water samples were collected. The aim of this study was to investigate the faecal and palatine tonsil carriage rate of Salmonella enterica and Yersinia enterocolitica in pigs at slaughter and the degree of carcass contamination by these bacteria. Typing of the isolates, virulence characterization and antimicrobial testing were also performed.S. enterica was isolated from 21.5% of the faecal samples, 10.9% of the carcasses and 10.4% of the tonsils, but not from scalding water. Nineteen different serovars were identified among 172 S. enterica isolates. The prevalent serovars were Derby (41.3%), Rissen (12.2%), Typhimurium (11%), 4,[5],12:i:— (8.7%) and Give (4.1%). S. enterica ser. Typhimurium and S. enterica ser. 4,[5],12:i:— isolates were phage-typed and PT DT120 was the most common (23.5%). Y. enterocolitica was detected in 17.1% of the faecal samples, 2.4% of the carcasses, 10.8% of the tonsils and 11.8% of the scalding water samples. A total of 119 isolates were found, four of them in water. Of the 115 Y. enterocolitica isolates of pig origin, 24 (20.9%) were 4/O:3 and 4 (3.5%) were 2/O:9. Y. enterocolitica 4/O:3 represented 85.7% of the pathogenic isolates found in all types of samples and 100% of those found in tonsils. In 4/O:3 isolates the most common virulence-associated genes were ystA (100%), inv (95.8%), ail (87.5%) and yadA (54.2%). In 2/O:9 isolates the prevalent genes were ail (100%), inv (100%) and ystA (100%), followed by ystB (25.0%). The majority (75.7%) of Y. enterocolitica isolates was biotype 1A, belonging to 13 serotypes (O:3; O:5; O:4,32-4,33; O:6,30-6,31; O:7,8-8; O:7,8-8-8,19; O:7,13; O:8; O:9; O:13; O:16-16,29; O:41,42-41,43; O:52). The most common virulence genes in 1A isolates were inv (95.4%) and ystB (72.4%).The antimicrobial resistance test showed that all Salmonella isolates were susceptible to cefotaxime, ciprofloxacin, cefalothin, gentamicin and enrofloxacin. Resistances to tetracycline (56%), sulphonamide compounds (42%) and streptomycin (34%) were the most common. All Y. enterocolitica isolates were susceptible to ciprofloxacin, ceftazidime, cefotaxime, chloramphenicol, enrofloxacin, gentamicin, kanamicin and neomycin. Most isolates were resistant to cefalothin (92%) and ampicillin (89%).Apparently, carcass contamination by S. enterica and Y. enterocolitica was more likely attributable to cross-contamination than to self-contamination, suggesting that good hygienic measures and slaughtering procedures can control transmission of these pathogens to pork meat.