Evaluation of virulence genes in Yersinia enterocolitica strains using SYBR Green real-time PCR

Design and Optimization of a yst-PCR to Detect Yersinia enterocolitica in Meat Food

In this study, a polymerase chain reaction (PCR) directed to the yst chromosomal gene (yst-PCR) was used as a rapid, sensitive, and specific method to detect Yersinia enterocolitica strains belonging to different biotypes in foods; a competitive Internal Amplification Control (cIAC) is also developed. The cIAC had a molecular weight of 417 bp and was detected until a concentration of 0.85 ng/μL. No other strains of other Yersinia species, nor Enterobacteriales order were detected by this PCR. In pure culture, the detection limit (DL) of the yst-PCR was lower for ystA+ strain (10 colony-forming unit [CFU]/mL) than for ystB+ strain (1 × 102 CFU/mL); which was the concentration detected in Y. enterocolitica inoculated minced meat. The proposed protocol included an enrichment step in peptone sorbitol bile (PSB) broth at 25°C for 24 h followed by isolation on Mac Conkey agar and chromogenic medium. An aliquot of the PSB broth homogenate and a loopful from the confluent zone of solid media were collected to perform DNA extraction for yst-PCR, and typical colonies were characterized by biochemical assays. Among 30 non-contaminated food samples, 4 samples were yst-positive and no Y. enterocolitica isolates were obtained. It is suggested that this yst-PCR could be used in the investigation of Y. enterocolitica in foods.

Traceability, virulence and antimicrobial resistance of Yersinia enterocolitica in two industrial cheese-making plants

Between 2018 and 2019, 309 environmental and food samples were collected from two industrial cheese-making plants located in Sardinia, in order to investigate Y. enterocolitica presence and to characterize the isolates. Y. enterocolitica isolates were further compared with isolates detected during a previous investigation from sheep and goat raw milk samples. Y. enterocolitica was detected in 7.4 % of the samples and the prevalence was higher, even if not significantly (P > 0.05) higher in non-food contact surface samples (10.2 %) than in food contact surface samples (3.8 %). The highest prevalence was detected in floor samples (13.5 %), followed by drain samples (7.2 %), which might serve as main harborage sites for further contamination. Y. enterocolitica was also detected in food contact surfaces, namely shelves of the Ricotta cooling room and packaging room, one cheese cutting machine surface and one raw milk filter sample. The biotype 1A isolates identified in this study were classified into six different serotypes. Additionally, a bioserotype 2/O:5,27 isolate was identified in one goat milk sample. All 1A isolates possessed the virulence genes invA and ystB while the 2/O:5,27 isolate showed the presence of ail, ystA, invA and yadA genes, thus confirming a pathogenic potential. The isolates showed intrinsic resistance to amoxicillin-clavulanic acid, ticarcillin and cefoxitin due to the presence of the blaA gene. Whole genome sequencing allowed to identify seven different sequence types among the 1A isolates, thus showing a high genetic diversity. The same Y. enterocolitica sequence type (ST3) was detected from three different areas of the same cheese-making plant, indicating a possible transfer of the microorganism along the processing lines. Y. enterocolitica contamination in cheese-making plants can pose a risk to human health. Preventive measures include the hygienic design of the plant layout and equipment, in association with proper cleaning and disinfection programmes.

Surveillance of Human Cases of Salmonellosis, Campylobacteriosis, Listeriosis, and Hepatitis A in Campania (Southern Italy): Seven-Year Monitoring (2013-2019)

Foodborne infections cause illness and death every year worldwide. The aim of this study was to describe trends in 2013-2019 in the occurrence of human cases of salmonellosis, campylobacteriosis, listeriosis, and hepatitis A in the Campania region. Human case data were provided by the National Surveillance System of disease and were grouped by year, province, age group, and sex. Moreover, the number of people hospitalized was recorded. In the Campania region, the total number of confirmed human cases for the diseases investigated was 1924, with Hepatitis A and the Salmonellosis as the first most reported (1009 and 825 cases, respectively). The incidence rates of gastroenteritis under study were lower than those in Italy and European Union in the same period, with the exception of Hepatitis A whose incidence was higher than that recorded in Italy. Data on hospitalizations pointed out the onset of severe forms of infection also for listeriosis and campylobacteriosis, whose incidence was very low (27 and 63 cases, respectively). Unfortunately, no information on the foods implicated is available. Although probably underestimated, gastroenteritis due to foodborne agents still represents a burden in Campania, and continuous monitoring and implementation of the currently available regional surveillance system is required.

Risk factors and the overall characterization of Yersinia enterocolitica as an initial model of pathogen surveillance in the pig production system in Serbia

A survey was undertaken to determine the overall prevalence of Yersinia enterocolitica in pigs of slaughter age and to characterize the isolates in relation to bio-serotype, the presence of virulence genes, genetic diversity, and antimicrobial resistance. Moreover, possible risk factors associated with Y. enterocolitica infection during the pre-harvested and harvested phase of pig production were studied. The overall Y. enterocolitica prevalence in the pigs was 10.4% (95% confidence interval, CI = 8.5-12.3%). The most common Y. enterocolitica bio-serotype was 4/O:3, accounting for 81.6% of investigated isolates. The pathogenicity of 63 Y. enterocolitica 4/O:3 isolates, originating from all infected farms, was confirmed by the presence of both the ail and ystA virulence-associated genes and the absence of ystB gene (100%). Characterization with PFGE of 63 confirmed Y. enterocolitica 4/O:3 isolates identified five different genotypes with shared identical genetic profiles (100% similarity) within each genotype. Isolates originating from farrow-to-finish farms were only resistant to ampicillin, while resistance to nalidixic acid, tetracycline, and chloramphenicol at fattening farms was also observed. Risk factors related to Y. enterocolitica pig infection include fattening farms (odds ratio, OR = 2.3, 95% CI = 1.4-3.8, P < 0.001), a 3-6 h lairage period (OR = 1.6, 95% CI = 1.0-2.6, P = 0.035) and winter season (OR = 3.8, 95% CI = 2.0-7.4, P < 0.001). In addition to the overall characterization of Y. enterocolitica isolates, identification of the main risks associated with infection allows better application of preventive measures to reduce the occurrence and distribution of Y. enterocolitica infection.

Pathogenic potential and antibiotic resistance of Yersinia enterocolitica, a foodborne pathogen limited to swine tonsils in a pork production chain from Southern Brazil

In this study, we aimed to characterize the distribution of Yersinia enterocolitica in a pork production chain in Brazil, as well as the virulence profile and antibiotic resistance of the obtained isolates. Samples from 10 pig lots obtained from finishing farms (water, feed, and barn floors, n = 30), slaughterhouse (lairage floors, carcasses at four processing steps, tonsils, and mesenteric lymph nodes, n = 610), and processing (end cuts, processing environment, n = 160) were obtained in Paraná state, Brazil, and subjected to Y. enterocolitica detection by ISO 10,273. The obtained isolates were identified based on biochemical and molecular features (16 s rRNA, inv, bioserotyping) and subjected to PCR assays to detect virulence (ail, ystA, ystB, virF, myfA, fepA, fepD, fes, tccC, ymoA, hreP, and sat) and multidrug resistance-related genes (emrD, yfhD, and marC). Also, isolates were subjected to disk diffusion test to characterize their resistance against 17 antibiotics from 11 classes and to pulsed field gel electrophoresis (PFGE) after XbaI macro-restriction. Y. enterocolitica was detected in a single sample (tonsil), and the obtained three isolates were characterized as serotype O:3, harboring ail, ystA, virF, myfA, tccC, ymoA, hreP, emrD, yfhD, and marC, and resistant to all tested antibiotics. The three isolates presented identical macro-restriction profiles by PFGE, also identical to isolates obtained from Minas Gerais, other Brazilian state; one selected isolate was identified as biotype 4. Despite the low occurrence of Y. enterocolitica in the studied pork production, the virulence potential and the antibiotic resistance profiles of the isolates demonstrated their pathogenic potential, and the macro-restriction profiles indicate strains descending from a common subtype in the pork production chain of two Brazilian States.

Evaluation of the Correlation between the mRNA Expression Levels of ystA and ymoA Genes in Y. enterocolitica Strains with Different Enterotoxic Properties

Yersinia enterocolitica is one of the main causative agents of human diarrhea. Pigs are a reservoir and the most common source of infection for humans. The aim of this study was to analyze the expression of ystA and ymoA genes in Y. enterocolitica strains with different enterotoxic properties, isolated from humans and pigs. The experiment involved two groups of Y. enterocolitica strains producing and not producing enterotoxin YstA, which were isolated from humans and pigs. All strains were ystA- and ymoA-positive. The expression of ystA and ymoA genes was analyzed by quantitative real-time PCR (qPCR). The relative expression level of the ystA gene was significantly higher than the expression level of the ymoA gene in Y. enterocolitica strains isolated from humans with clinical symptoms of yersiniosis. In other strains, a significant decrease in ystA gene transcription was observed, and the relative expression level of the ymoA gene was significantly higher than the expression level of the ystA gene. Statistically significant differences were not observed in either group of strains isolated from pigs. The results of our study revealed a correlation between mRNA expression levels of ystA and ymoA genes in Y. enterocolitica strains isolated from humans.

Comparison of droplet digital PCR vs real-time PCR for Yersinia enterocolitica detection in vegetables

Yersiniosis - the 4th most commonly reported zoonosis in the European Union - is caused by the consumption of food contaminated with the bacterium Yersinia enterocolitica. The number of human cases and contaminated food samples is probably underestimated since conventional molecular methods currently proposed for Yersinia enterocolitica detection proved to have several limitations. Critical issues associated with the detection of Yersinia enterocolitica in meat and/or meat product has already been investigated, whereas data on the possible limits of the molecular methods for Yersinia enterocolitica detection in vegetables are still lacking. According to ISO method (ISO 18867:2015), real-time polymerase chain reaction (rtPCR) should be adopted for Yersinia enterocolitica detection, even if it proved to be affected by some biases. Recently, Droplet Digital PCR (ddPCR) has been introduced as a useful tool to detect and quantify different pathogenic bacteria in complex food matrices. However, its potential application for Yersinia enterocolitica detection in vegetables has never been investigated before. In the present study two molecular platforms (rtPCR and ddPCR) were used to evaluate the pathogen's behaviour in experimentally contaminated leafy greens (Lactuca sativa L.) and to assess the rate of detection achievable after the incubation for eleven days at different temperatures. By comparing, noticeable differences emerged between the two technical approaches: only ddPCR allowed the detection of the pathogen in leafy greens when contaminated at low levels. Moreover, results of the present work highlighted the importance of length and temperature of incubation on the survival and/or the growth of Yersinia enterocolitica in vegetables: at 18 and 25 °C the concentration of the pathogen considerably decreases along incubation. Based on data, the use of rtPCR leads to an underestimation of the true prevalence of pathogenic Y. enterocolitica in vegetables, while temperature and time currently proposed for Y. enterocolitica (25 °C for 24 h), allow optimizing detection. To conclude, ddPCR may be undoubtedly proposed as a reliable alternative strategy for the quick detection of the pathogen in food samples.

Evidence of Antimicrobial Resistance and Presence of Pathogenicity Genes in Yersinia enterocolitica Isolate from Wild Boars

Yersinia enterocolitica (Ye) is a very important zoonosis andwild boars play a pivotal role in its transmission. In the last decade, the wild boar population has undergone a strong increase that haspushed them towards urbanized areas, facilitating the human–wildlife interface and the spread of infectious diseases from wildlife to domestic animals and humans. Therefore, it is important to know the serotype, antimicrobial resistance and presence of pathogenicity genes of Yersinia enterocolitica (Ye) isolated in species. From 2013 to 2018, we analyzed the liver of 4890 wild boars hunted in Liguria region; we isolated and serotyped 126 Ye positive samples. A decisive role in the pathogenicity is given by the presence of virulence genes; in Ye isolated we found ystB (~70%), ymoA (45.2%), ail (43.6%) and ystA (~20%). Moreover, we evaluated the susceptibility at various antimicrobic agents (Ampicillin, Chloramphenicol, Enrofloxacin, Gentamicin, Kanamycin, Trimethoprim–Sulfamethoxazole, Sulfisoxazole, Ceftiofur and Tetracycline). The antibiotic resistance was analyzed, and we found a time-dependent increase. It is important to shed light on the role of the wild boars as a reserve of potentially dangerous diseases for humans, and also on the antibiotic resistance that represents a public health problem.

Virulence genotyping and antimicrobial resistance profiles of Yersinia enterocolitica isolated from meat and meat products in Egypt

Pathogenic Yersinia enterocolitica (Y. enterocolitica) is one of the food-borne entero-pathogen responsible for yersiniosis in humans. The purpose of this research was to survey the prevalence, virulence-associated genes, and antimicrobial resistance of Y. enterocolitica isolated from meat and meat product samples in Egypt. Forty-one (5.9%) out of 700- samples of chicken meat, beef, ground beef, and sausage were positive Y. enterocolitica with a high prevalence in chicken meat (12%). Five virulence genes (ail, inv, ystA, ystB, and yadA) were characterized among 41 Y. enterocolitica isolates with variable frequencies. Among the strains tested, the ystB gene was detected with a high percentage (78.1%), followed by inv gene (70.7%), ail gene (14.6%), ystA gene (12.2%), and yadA gene (2.4%). A high resistance rate was estimated to amoxicillin-clavulanic acid (100%), followed by cefazolin (95%), ampicillin (65.9%), and doxycycline (51.2%), whilst a high sensitivity rate was observed to gentamicin and ciprofloxacin (97.6% each). Interestingly, the multidrug resistance was specified in the 70.7% of strains and showing 13 resistance patterns. Based on nucleotide sequence analysis of the 16s rRNA gene, the phylogenetic tree showed the genetic relatedness amongst Y. enterocolitica isolates. These findings highlighted the emergence of virulent and multidrug-resistant pathogenic Y. entrocolitica in retailed meat and meat products in Egypt.

Prevalence of Enteropathogens and Virulence Traits in Brazilian Children With and Without Diarrhea

The use of molecular diagnostics for pathogen detection in epidemiological studies have allowed us to get a wider view of the pathogens associated with diarrhea, but the presence of enteropathogens in asymptomatic individuals has raised several challenges in understanding the etiology of diarrhea, and the use of these platforms in clinical diagnosis as well. To characterize the presence of the most relevant bacterial enteropathogens in diarrheal episodes, we evaluated here the prevalence of diarrheagenic E. coli pathotypes, Salmonella spp., and Yersinia enterocolitica in stool samples of children with and without diarrhea using real-time quantitative PCR (qPCR). We found that the presence of genetic markers associated with bacterial pathogens was significantly higher in stool samples from the diarrhea group compared to the control (P < 0.001). Bacterial loads in samples positive for eae and aggR markers were also determined. Compared to samples from asymptomatic children, a significantly higher number of copies of the eae gene were found in diarrhea samples. Also, the presence of genetic markers associated with STEC strains with clinical significance was evaluated in eae-positive samples by high-throughput real-time PCR. The data presented herein demonstrated that asymptomatic children of an urban area in Brazil might be enteropathogen reservoirs, especially for STEC.

Evaluation of microbial contamination of different pork carcass areas through culture-dependent and independent methods in small-scale slaughterhouses

Routine evaluation of the slaughter process is performed by the enumeration of the aerobic colony count, Enterobacteriaceae and Salmonella spp. on the carcass through destructive or non-destructive methods. With non-destructive methods, bacteria are counted from a minimum area of 100 cm² in different sampling sites on the pork carcasses, and the results of these investigated areas are pooled to one value for the complete carcass evaluation (a total of 400 cm²). However, the composition of the bacterial community present on the different sampling areas remains unknown. The aim of the study was to characterize the microbial population present on four areas (ham, back, jowl and belly) of eight pork carcasses belonging to two different slaughterhouses through culture-dependent (Matrix-assisted laser desorption/ionization time-of-flight Mass Spectrometry MALDI-TOF MS, combined with 16S rRNA gene sequencing) and complementary culture-independent (16S rRNA amplicon sequencing) methods. The presence of Salmonella spp. and Y. enterocolitica was additionally assessed. Using MALDI-TOF MS, Staphylococcus, Pseudomonas, and Escherichia coli were found to dominate the bacterial cultures isolated from the 8 carcasses. Based on the 16S rRNA amplicon sequencing analyses however, no specific genus clearly dominated the bacterial community composition. By using this culture-independent method, the most abundant genera in microbial populations of the ham, back, jowl and belly were found to be similar, but important differences between the two slaughterhouses were observed. Thus, present data suggests that the indigenous bacterial population of individual animals is overruled by the microbial population of the slaughterhouse in which the carcass is handled. Also, our data suggests that sampling of only one carcass area by official authorities may be appropriate for the evaluation of the hygienic status of the carcasses and therefore of the slaughter process.

Is Yersinia bercovieri Surpassing Yersinia enterocolitica in Wild Boars (Sus scrofa)?

Yersiniosis was the fourth reported zoonosis in the European Union in 2018. As well-known, pigs are recognized important reservoirs of Yersinia enterocolitica. The study was focused on Y. enterocolitica detection in mesenteric lymph nodes and faeces of 305 wild boars, but Yersinia bercovieri was more common, being isolated from 108 animals (35.4%). Cold season (p = 1.17 × 10^-5) and young age (p = 0.004) significantly increased Y. bercovieri detection. Y. enterocolitica 1A belonging to six serotypes (O:4.32-4.33; O:5; O:6.30-6.31; O:7.8-8-8.19; O:10-34; O:12.25-12.26) was isolated from 8.2% (25/305) of the animals. Cold season significantly affected (p = 0.037) Y. enterocolitica detection.

Detection and quantification of Campylobacter in foods: New analytic approaches to detect and quantify Campylobacter spp. in food samples

The aim of the present study was to develop rapid qualitative and quantitative methods based on the use of Real-Time PCR and Droplet Digital PCR (ddPCR), in order to have reliable techniques to detect and quantify Campylobacter spp. in food samples. The gene 16S-rRNA was used as specific target for Campylobacter spp. Real- Time PCR evaluation assay and a not competitive internal control was ushered in it. To investigate the selectivity of the method, 26 Campylobacter strains and 40 non-Campylobacter strains were tested and in order to verify the application of Real- Time PCR method, 5 pork meat samples were experimentally inoculated with a Campylobacter jejuni strain. Subsequently, dilutions with a bacterial load of Campylobacter jejuni within 10-106 CFU/mL were chosen for the optimization of the ddPCR assay. Lastly, a total of 54 naturally contaminated foods samples were analyzed through molecular (Real-Time PCR and ddPCR) and traditional methods. The Real-Time PCR protocol demonstrated to amplify only the Campylobacter spp. strains and when Campylobacter jejuni was experimentally inoculated in meat samples the pathogen was always detected. The ddPCRs assay allowed to quantify a level of contamination of 10 CFU/mL, but it was unable to quantify levels of 105 - 106 CFU/mL. Lastly, Campylobacter spp. was never detected in the 54 samples tested. In conclusion, the novel analytic approach proposed, based on an initial screening of the samples with Real-Time PCR and then on quantification of Campylobacter spp. with a ddPCR on those positive, represents a quick monitoring tool and, if used correctly, it would allow the implementation of food safety.

Yersinia enterocolitica detection in pork products: Evaluation of isolation protocols

Conventional methods for Yersinia enterocolitica detection in food samples are generally considered inadequate. Problems arise from the presence of the so-called "background flora", coupled to the low contamination level of the pathogen. Since, data on the microbial ecology occurring in competitive microflora are still lacking, MALDI TOF MS was used for strains 'identification after enrichment in PSB or ITC broths, and after plating on selective CIN medium at different incubation times. SYBR Green Real time PCR was used for the Y. enterocolitica strains' detection (4/O:3, 1A/O:5) in experimentally contaminated foods, as well as in naturally contaminated samples. A higher number of different bacterial genera (10 on CIN and 18 on PCA) was recorded after enrichment in PSB, whilst enrichment in ITC led to recovery of 6 and 10 genera on CIN and PCA, respectively. Yersiniaceae was the dominant family on the first day of incubation, but on the second day the percentage of isolation considerably decreased. By testing experimentally contaminated samples, substantial difficulties were encountered. The biotype 1A was always detected, whereas strain 4/O:3 proved to be poorly competitive. Based on the data, the enrichment media PSB and ITC, currently proposed for Y. enterocolitica detection, need to be improved to promote a successful pathogen's recovery.

Yersinia enterocolitica-specific modulation of innate immune responses in jejunal epithelial cells

Gut is often subject to infection by different pathogens like Y. enterocolitica. To date, biotypes (BTs) 1A have been considered as non-pathogenic, because they do not express plasmid of virulence pYV; however, BTs 1A strains present other chromosomic virulence genes and recent studies suggest an implication of this microorganism in reactive arthritis. Although many studies highlighted the molecular basis of pathogenesis of Ye infection, scanty data are available about several environmental BTs 1A strains, often isolated in cases of foodborne disease but not included in pathogenicity studies. The aim of our work was to verify the ability of different Ye 1A strains to adhere and penetrate IPEC-J2 cells and to modulate intestinal innate immunity. Our results showed that all strains under study were able to adhere and penetrate enterocytes, causing inflammatory responses. Indeed, adhesion and invasion of enterocytes is an essential step in Ye pathogenesis (Fàbrega and Vila, 2012). Moreover, our data suggest the possible involvement of strains Ye2/O:9 in reactive arthritis, due to their ability (i) to penetrate enterocytes as pathogenic Ye1/O:8 strains do, and (ii) to increase IL-6, IL-8, IL-12 and IL-18 release. Lastly, our results confirm that IPEC-J2 cells are a very good model to evaluate host-pathogen interaction, and indicate IL-8, TNF-α, TLRs1 and 4 as possible markers of the ability of Ye strains to penetrate enterocytes. Moreover, we showed that Ye strains differently affect the host's innate immune responses.

Effect of low doses of biocides on the antimicrobial resistance and the biofilms of Cronobacter sakazakii and Yersinia enterocolitica

The susceptibility of Cronobacter sakazakii ATCC 29544 (CS) and Yersinia enterocolitica ATCC 9610 (YE) to sodium hypochlorite (10% of active chlorine; SHY), peracetic acid (39% solution of peracetic acid in acetic acid; PAA) and benzalkonium chloride (BZK) was tested. Minimum inhibitory concentration (MIC) values (planktonic cells; microdilution broth method) of 3,800 ppm (SHY), 1,200 ppm (PAA) and 15 ppm (BZK) for CS, and 2,500 ppm (SHY), 1,275 ppm (PAA) and 20 ppm (BZK) for YE, were found. In some instances, an increase in growth rate was observed in presence of sub-MICs (0.25MIC, 0.50MIC or 0.75MIC) of biocides relative to the samples without biocides. The cultures exhibited an acquired tolerance to biocides and an increase in antibiotic resistance after exposure to sub-MICs of such disinfectants. Strains were able to form strong biofilms on polystyrene after 48 hours (confocal laser scanning microscopy), with average biovolumes in the observation field (14,161 µm2) of 242,201.0 ± 86,570.9 µm3 (CS) and 190,184.5 ± 40,860.3 µm3 (YE). Treatment of biofilms for 10 minutes with disinfectants at 1MIC or 2MIC reduced the biovolume of live cells. PAA (YE) and BZK (CS and YE) at 1MIC did not alter the percentage of dead cells relative to non-exposed biofilms, and their effect of countering biofilm was due principally to the detachment of cells. These results suggest that doses of PAA and BZK close to MICs might lead to the dissemination of live bacteria from biofilms with consequent hazards for public health.

The design, validation and clinical verification of an in-house qualitative PCR to detect Yersinia enterocolitica and Yersinia pseudotuberculosis in faeces

Yersiniosis is a zoonotic foodborne infection of public health significance. The aim of this study was to design and validate a simple, accurate and cost-effective polymerase chain reaction (PCR) to detect pathogenic Yersinia spp. in faecal samples. An intercalating dye (EvaGreen)-based real-time multiplex PCR assay was designed to detect yadA, ystB and inv by melt curve analysis, allowing undifferentiated detection of all Yersinia enterocolitica biotypes, including biotype 1A, and Yersinia pseudotuberculosis. The assay was validated using cultured bacteria and clinical samples. A total of 107 positive and 51 negative samples were tested. The sensitivity and specificity was 98% and 100%. The limit of detection was 10⁴-10⁵ CFU/g faeces. A total of 605 samples (9 positive) were tested in the clinical verification with an accuracy and negative predictive value of 99% [95% confidence interval (CI) 97.9-99.6%] and 99.8% (95% CI 97.9-99.6%), respectively. This is an accurate, simple and cost-effective assay for the detection of pathogenic Yersinia spp.

Assessment of microbial communities on freshly killed wild boar meat by MALDI-TOF MS and 16S rRNA amplicon sequencing

Wild boars (Sus scrofa) are the most widely distributed large mammals and recent increase in consumption of wild boar meat urges the need of microbiological quality criteria. The aim of the study was to characterize the initial bacterial contamination on freshly-killed wild boar meat using a culture-dependent approach with ISO-methods combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification and 16S rRNA amplicon sequencing. Moreover, the presence of foodborne pathogens was examined using Real-Time-PCR and confirmed by classical isolation. Analysing 22 unrelated wild boar meat samples showed a higher bacterial contamination level compared to pork, with Salmonella present in almost one third of the samples. A great variability of the microbial contamination between the samples was recorded, as well as complementary results between culturing and 16S rRNA amplicon sequencing as frequently isolated genera were not always detected, and vice versa. Furthermore, the foodborne pathogen Salmonella was never detected with 16S rRNA amplicon sequencing, demonstrating the necessity for a cautious approach in the implementation of new analysis techniques in food safety. The present work determines that attention should be paid to the trade of non-inspected meat directly to retail or consumers.

Prevalence, bioserotyping and antibiotic resistance of pathogenic Yersinia enterocolitica detected in pigs at slaughter in Sardinia

The aims of the present study were to determine Yersinia enterocolitica prevalence in finishing pigs and piglets at slaughter and to characterize the isolates in terms of bioserotype, virulence profile, antimicrobial susceptibility and genetic diversity. During the years 2013-2014, nine pig slaughterhouses placed in Sardinia (Italy) were visited twice, in order to collect animal samples and scalding water. Overall, 609 samples respectively of tonsils (126), colon content (161), mesenteric lymph nodes (161) and carcass surfaces (161) were collected from 126 finishing pigs and 35 piglets. Moreover, 18 scalding water samples were collected. Samples were analyzed for the detection of Y. enterocolitica according to ISO 10273-2003 standard (with some modifications). With regard to finishing pigs, Y. enterocolitica was detected in 11.9% of colon content samples, 3.2% of tonsils and 2.4% of lymph nodes. In piglets, Y. enterocolitica prevalence was 8.6% in colon content and 2.8% lymph nodes samples. Y. enterocolitica was not detected from carcass surface samples of both finishing pigs and piglets and from scalding water samples. Isolates were bio- and serotyped, tested for the presence of four virulence genes by PCR (ail, ystA, ystB and inv) and for antimicrobial resistance by disc-diffusion method. Among 47 confirmed isolates, 33 (70.2%) belonged to bio-serotype 4:O3, 7 (14.9%) to bio-serotype 2/O:5 and 7 (14.9%) to bio-serotype 1A. Bio-serotype 1A was detected only in isolates of piglets' samples. In bio-serotype 4/O:3 isolates the most common virulence genes were ystA (97.0%), ail (84.8%) and inv (78.8%). In bio-serotype 2/O:5, ail, inv and ystA genes were detected in all of the isolates. All bio-serotype 1A isolates were ystB positive (lacking ail, inv and ystA). All isolates were susceptible to cefotaxime, ceftazidime, chloramphenicol, ciprofloxacin, enrofloxacin, gentamicin, nalidixic acid, sulphonamide, tetracycline and trimethoprim-sulphametoxazole. Resistances to ampicillin and cefalothin were the most common (100%), followed by amoxicillin/clavulanic acid (83.0%) and streptomycin (4.3%). Resistance to amoxicillin/clavulanic acid was detected in 57% of bio-serotype 4/O:3 isolates, 71% of bio-serotype 1A and 100% of bio-serotype 2/O:5 isolates. Two bio-serotype 4/O:3 isolates (6%) were resistant to streptomycin. Thirty-two pathogenic Y. enterocolitica isolates were tested by NotI-PFGE, which identified 5 patterns among bio-serotype 4/O:3 isolates and 2 patterns among bio-serotype 2/O:5 isolates. This study provides epidemiological data about human pathogenic Y. enterocolitica and highlight the role of pigs as a potential source of infection for the consumers in Sardinia.

Yersinia enterocolitica in Italy: A Case of Septicemia and Abdominal Aortic Aneurysm Infection

We report a case of Yersinia enterocolitica septicemia in a 63-year-old patient admitted to the Vascular Surgery Department of Umberto I Hospital (Rome, Italy) for an abdominal aortic aneurysm. The microorganism, recovered from both peripheral blood cultures and aneurysmatic aortic wall specimens, was identified as Y. enterocolitica using matrix-assisted laser desorption ionization-time of flight analysis (MALDI-TOF MS) and 16S rDNA gene sequencing. The isolate responsible for septicemia belonged to the O:9 serotype (biogroup 2). A genetic screening of the isolate made it possible to detect the presence of both the yst and ail genes, encoding a heat-stable enterotoxin and a protein involved in invasion/adherence and serum resistance, respectively. Our case contributes in enriching epidemiological data concerning Y. enterocolitica infections, which might represent severe complications in patients suffering from cardiovascular diseases. Moreover, this study, together with the others, should be regarded as valuable and useful tools for monitoring the rate of infections worldwide.

Yersinia enterocolitica biotype 1A: a possible new trigger of reactive arthritis

Yersinia enterocolitica (YE) biotype 1A is generally considered non-pathogenic, and the role of it in causing reactive musculoskeletal complications is unclear. We evaluated the capability of YE biotype 1A to induce reactive arthritis (ReA) and other reactive musculoskeletal symptoms. Analysis of self-reported musculoskeletal symptoms was supplemented with a telephone interview (with a permission to acquire copies of patient files from a local physician or hospital) and/or clinical examination of subjects with recent musculoskeletal symptoms after a positive stool culture for YE. The diagnoses of ReA and reactive tendinitis and enthesitis (ReTe) were defined as "definite" when based on clinical examination and/or on interview by phone and "probable" when based solely on the questionnaire. Of 120 subjects, who reported musculoskeletal symptoms, 100 were included in the final analysis. Among these 100 patients, 68% had YE biotype 1A, 16% YE bio/serotype 4, and 1% biotype 2 infection; the remaining 15% had different YE-like strains or a non-biotypable strain. Of the 21 patients with ReA and of the 14 patients with ReTe, the diagnosis was definite in 9 and 7 patients and probable in 12 and 7 patients, respectively. The clinical picture of ReA caused by YE biotype 1A was similar with other bio/serotypes of YE. The definite ReA due to YE biotype 1A occurred in middle-aged adults (5 men, 4 women) with the most frequently affected joints being the knees and ankles. We suggest that YE biotype 1A should be taken into account as a new trigger of ReA.