Qualitative and Quantitative Detection of Human Pathogenic Yersinia enterocolitica in Different Food Matrices at Retail Level in Bavaria

Prevalence and Persistence of Multidrug-Resistant Yersinia enterocolitica 4/O:3 in Tonsils of Slaughter Pigs from Different Housing Systems in Croatia

Yersinia enterocolitica is one of the priority biological hazards in pork inspection. Persistence of the pathogen, including strains resistant to antimicrobials, should be evaluated in pigs from different housing systems for risk ranking of farms. In this 2019 study, tonsils were collected from 234 pigs, of which 69 (29.5%) were fattened on 3 big integrated farms, 130 (55.5%) on 10 medium-sized farms, and 35 (15%) on 13 small family farms. In addition, 92 pork cuts and minced meat samples from the same farms were tested for the presence of Y. enterocolitica using the culture method. Phenotypic and genetic characteristics of the isolates were compared with previously collected isolates from 2014. The overall prevalence of Y. enterocolitica in pig tonsils was 43% [95% CI 36.7−49.7]. In pigs from big integrated, medium-sized, and small family farms, the prevalence was 29%, 52%, and 40%, respectively. All retail samples of portioned and minced pork tested negative for pathogenic Y. enterocolitica, likely due to high hygienic standards in slaughterhouses/cutting meat or low sensitivity of culture methods in these matrices. The highest recovery rate of the pathogen from tonsils was found when alkali-treated PSB and CIN agar were combined. The biosecurity category of integrated and medium farms did not affect the differences in prevalence of Y. enterocolitica (p > 0.05), in contrast to family farms. Pathogenic ail-positive Y. enterocolitica biotype 4 serotype O:3 persisted in the tonsils of pigs regardless of the type of farm, slaughterhouse, and year of isolation 2014 and 2019. PFGE typing revealed the high genetic concordance (80.6 to 100%) of all the Y. enterocolitica 4/O:3 isolates. A statistically significant higher prevalence of multidrug-resistant Y. enterocolitica 4/O:3 isolates was detected in the tonsils of pigs from big integrated farms compared to the other farm types (p < 0.05), with predominant and increasing resistance to nalidixic acid, chloramphenicol, and streptomycin. This study demonstrated multidrug resistance of the pathogen in pigs likely due to more antimicrobial pressure on big farms, with intriguing resistance to some clinically relevant antimicrobials used in the treatment of yersiniosis in humans.

Virulence Determinants and Genetic Diversity of Yersinia Species Isolated from Retail Meat

Yersinia enterocolitica is an important foodborne pathogen, and the determination of its virulence factors and genetic diversity within the food chain could help understand the epidemiology of yersiniosis. The aim of the present study was to detect the prevalence, and characterize the virulence determinants and genetic diversity, of Yersinia species isolated from meat. A total of 330 samples of retailed beef (n = 150) and pork (n = 180) in Latvia were investigated with culture and molecular methods. Whole genome sequencing (WGS) was applied for the detection of virulence and genetic diversity. The antimicrobial resistance of pathogenic Y. enterocolitica isolates was detected in accordance with EUCAST. Yersinia species were isolated from 24% (79/330) of meats, and the prevalence of Y. enterocolitica in pork (24%, 44/180) was significantly higher (p < 0.05) than in beef (13%, 19/150). Y. enterocolitica pathogenic bioserovars 2/O:9 and 4/O:3 were isolated from pork samples (3%, 6/180). Only resistance to ampicillin was confirmed in Y. enterocolitica 4/O:3 and 2/O:9 isolates, but not in other antimicrobials. Major virulence determinants, including ail, inv, virF, ystA and myfA, were confirmed with WGS in Y. enterocolitica 2/O:9 and 4/O:3. MLST typing revealed 15 STs (sequence types) of Y. enterocolitica with ST12 and ST18, which were associated with pathogenic bioserovars. For Y. enterocolitica 1A, Y. kristensenii, Y. intermedia and Y. frederiksenii, novel STs were registered (ST680-688). The presence of virulence genes and genetic characteristics of certain Y. enterocolitica STs confirm the common knowledge that pork could be an important source of pathogenic Yersinia.

Meat Safety from Farm to Slaughter—Risk-Based Control of Yersinia enterocolitica and Toxoplasma gondii

The implementation of the traditional meat safety control system has significantly contributed to increasing food safety and public health protection. However, several biological hazards have emerged in meat production, requiring a comprehensive approach to their control, as traditional methods of meat inspection at the slaughterhouse are not able to detect them. While national control programs exist for the most important meat-related hazards, similar data are still lacking for certain neglected threats, such as Yersinia enterocolitica or Toxoplasma gondii. The obstacle in controlling these hazards in the meat chain is their presence in latently infected, asymptomatic animals. Their effective control can only be achieved through systematic preventive measures, surveillance or monitoring, and antimicrobial interventions on farms and in slaughterhouses. To establish such a system, it is important to collect all relevant data on hazard-related epidemiological indicators from the meat chain, which should provide relevant guidance for interventions at the harvest and post-harvest stage. The proposed approach is expected to improve the existing system and provide many opportunities to improve food safety and public health.

Yersiniosis in New Zealand

The rate of yersiniosis in New Zealand (NZ) is high compared with other developed countries, and rates have been increasing over recent years. Typically, >99% of human cases in NZ are attributed to Yersinia enterocolitica (YE), although in 2014, a large outbreak of 220 cases was caused by Yersinia pseudotuberculosis. Up until 2012, the most common NZ strain was YE biotype 4. The emergent strain since this time is YE biotype 2/3 serotype O:9. The pathogenic potential of some YE biotypes remains unclear. Most human cases of yersiniosis are considered sporadic without an identifiable source. Key restrictions in previous investigations included insufficient sensitivity for the isolation of Yersinia spp. from foods, although foodborne transmission is the most likely route of infection. In NZ, YE has been isolated from a variety of sick and healthy domestic and farm animals but the pathways from zoonotic reservoir to human remain unproven. Whole-genome sequencing provides unprecedented discriminatory power for typing Yersinia and is now being applied to NZ epidemiological investigations. A "One-Health" approach is necessary to elucidate the routes of transmission of Yersinia and consequently inform targeted interventions for the prevention and management of yersiniosis in NZ.

Prevalence of pathogenic Yersinia enterocolitica in minced meat, pig tongues and hearts at the retail level in the Czech Republic detected by real time PCR

Yersiniosis is the third most frequently reported zoonosis in the European Union and Yersinia enterocolitica is the most common species causing human infections. Pigs are assumed to be the main reservoir of human pathogenic Y. enterocolitica with the presence of bacteria mainly in the tonsils and intestinal content. Undercooked pork and pork products have been suggested as the primary source of human yersiniosis. Nevertheless, data on the prevalence of pathogenic Y. enterocolitica in foodstuffs including pork products are very limited. A molecular based method (real time PCR) targeting the ompF gene (detection of Yersinia genus) and the ail gene (a chromosomally located virulence marker of Y. enterocolitica) was used to determine the prevalence of pathogenic Y. enterocolitica in minced meat and edible pork offal at the retail level in the Czech Republic. A total of 50 pig tongues, 50 pig hearts, and 93 samples of minced meat containing pork were purchased at nine retail outlets in Brno. High detection rates of Yersinia spp. were found in all types of samples (pig tongues, 80.0%; pig hearts, 40.0%; and minced meat, 55.9%). The highest prevalence of pathogenic Y. enterocolitica was found in pig tongues (40.0%), followed by pig hearts (18.0%) and minced meat samples (17.2%). Although from the point of view of food safety the merely molecular detection of DNA of the pathogenic bacteria could represent a false positive result, our results indicate the presence of pathogenic Y. enterocolitica in raw pork products at the retail level in the Czech Republic, which may pose a risk of consumer infection. Sufficient heat treatment and prevention of cross-contamination during preparation of food in the kitchen should be recommended.

High prevalence of pathogenic Yersinia enterocolitica in pig cheeks

Samples from pork cuts for minced meat and cheeks from processing plants and a slaughterhouse, and modified atmosphere (MA) packaged pork from retail were studied to estimate the prevalence of pathogenic, i.e. virulence plasmid bearing, Yersinia enterocolitica and Yersinia pseudotuberculosis in pork, as well as to quantify pathogenic Y. enterocolitica in pork cuts. Pathogenic (virF-positive) Y. enterocolitica was isolated from 17 pig cheeks (23%) but not from any of the MA-packaged 54 retail pork samples and only from one of the 155 pork cut (0.6%). Most (16/17) of the cheek samples were contaminated with pathogenic Y. enterocolitica 4/O:3 and one with bioserotype 2/O:9. No Y. pseudotuberculosis was isolated. The prevalence of pathogenic Y. enterocolitica was clearly higher (39%) in 155 pork cuts when studied with nested PCR targeting yadA on the virulence plasmid pYV although the contamination level was low varying between 0.1 and 1.6 MPN/g. Raw pork cuts and especially pig cheeks may serve as possible sources for yersiniosis caused by pathogenic Y. enterocolitica.

Occurrence of zoonotic clostridia and Yersinia in healthy cattle

Zoonotic pathogens are a frequent cause of disease worldwide. This study was designed to determine the occurrence of Clostridium difficile, Clostridium botulinum, and Yersinia enterocolitica in cattle in southern Bavaria, Germany. The study population included 49 farms; 34 were dairy farms (30 also fattening beef cattle) and 15 were solely beef cattle farms. Fecal and dust samples were collected from summer 2011 to summer 2012 and analyzed using a combination of enrichment procedures and real-time PCR. For the detection of C. difficile, samples were screened for the presence of the tpi gene and toxin genes tcdA, tcdB, and cdtA. Samples also were screened for genes for C. botulinum toxins A through F and for the ail gene of Y. enterocolitica. Of 506 samples, C. difficile genes were found in 29 samples (5.7%): 25 samples from dairy farms and 4 samples from beef cattle farms. Toxin genes were identified in 17 samples, with toxigenic profiles of A(+)B(+)CDT(-), A(+)B(-)CDT(+), and A(+)B(+)CDT(+). C. botulinum toxin genes were not detected in fecal samples from cattle, but the gene for toxin B was detected in 1 (0.8%) of 125 dust samples. Y. enterocolitica genes were found in 6 (1.6%) of 382 fecal samples from three dairy farms and one beef cattle farm. This study revealed that C. difficile and Y. enterocolitica are rare on cattle farms in Bavaria, Germany. In contrast to results of previous studies, C. botulinum was not detected in fecal samples but was found very rarely in dust samples from the cattle environment.

Quantification of Yersinia enterocolitica in raw milk using qPCR

This report describes a new, sensitive and specific protocol for rapid detection and quantification of Yersinia enterocolitica in artificially contaminated raw milk samples. The new method is based on an optimized real-time PCR protocol with a TaqMan probe. The primers and probe are based on the chromosomal ail gene. This method was successful for both intended uses: (1) direct detection and quantification of Y. enterocolitica in artificially and naturally contaminated raw milk samples and (2) characterization of growth potential of different serotypes of Y. enterocolitica in raw milk at the most commonly used storage temperatures. The recent method eliminates the pre-PCR enrichment step, which makes it possible to quickly assess milk-related consumer exposure to this pathogen.