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

Detection and Characterization of Zoonotic Pathogens in Game Meat Hunted in Northwestern Italy

Wildlife can represent a reservoir of zoonotic pathogens and a public health problem. In the present study, we investigated the spread of zoonotic pathogens (Salmonella spp., Yersinia enterocolitica, Listeria monocytogenes, Shiga-toxin-producing Escherichia coli (STEC), and hepatitis E virus (HEV)) considering the presence of virulence and antibiotic resistance genes in game meat from animals hunted in northwest Italy. During two hunting seasons (2020 to 2022), samples of liver and/or muscle tissue were collected from chamois (n = 48), roe deer (n = 26), deer (n = 39), and wild boar (n = 35). Conventional microbiology and biomolecular methods were used for the detection, isolation, and characterization of the investigated pathogens. Two L. monocytogenes serotype IIa strains were isolated from wild boar liver; both presented fosfomycin resistance gene and a total of 22 virulence genes were detected and specified in the text. Eight Y. enterocolitica biotype 1A strains were isolated from chamois (2), wild boar (5), and deer (1) liver samples; all showed streptogramin and beta-lactam resistance genes; the virulence genes found were myfA (8/8 strains), ymoA (8/8), invA (8/8), ystB (8/8), and ail (4/8). Our data underscore the potential role of wildlife as a carrier of zoonotic and antibiotic-resistant pathogens in northwest Italy and a food safety risk for game meat consumers.

Hunted Wild Boars in Sardinia: Prevalence, Antimicrobial Resistance and Genomic Analysis of Salmonella and Yersinia enterocolitica

The objective of this investigation was to evaluate Salmonella and Yersinia enterocolitica prevalence in wild boars hunted in Sardinia and further characterize the isolates and analyse antimicrobial resistance (AMR) patterns. In order to assess slaughtering hygiene, an evaluation of carcasses microbial contamination was also carried out. Between 2020 and 2022, samples were collected from 66 wild boars hunted during two hunting seasons from the area of two provinces in northern and central Sardinia (Italy). Samples collected included colon content samples, mesenteric lymph nodes samples and carcass surface samples. Salmonella and Y. enterocolitica detection was conducted on each sample; also, on carcass surface samples, total aerobic mesophilic count and Enterobacteriaceae count were evaluated. On Salmonella and Y. enterocolitica isolates, antimicrobial susceptibility was tested and whole genome sequencing was applied. Salmonella was identified in the colon content samples of 3/66 (4.5%) wild boars; isolates were S. enterica subs. salamae, S. ser. elomrane and S. enterica subs. enterica. Y. enterocolitica was detected from 20/66 (30.3%) wild boars: in 18/66 (27.3%) colon contents, in 3/66 (4.5%) mesenteric lymph nodes and in 3/49 (6.1%) carcass surface samples. In all, 24 Y. enterocolitica isolates were analysed and 20 different sequence types were detected, with the most common being ST860. Regarding AMR, no resistance was detected in Salmonella isolates, while expected resistance towards β-lactams (blaA gene) and streptogramin (vatF gene) was observed in Y. enterocolitica isolates (91.7% and 4.2%, respectively). The low presence of AMR is probably due to the low anthropic impact in the wild areas. Regarding the surface contamination of carcasses, values (mean ± standard deviation log10 CFU/cm2) were 2.46 ± 0.97 for ACC and 1.07 ± 1.18 for Enterobacteriaceae. The results of our study confirm that wild boars can serve as reservoirs and spreaders of Salmonella and Y. enterocolitica; the finding of Y. enterocolitica presence on carcass surface highlights how meat may become superficially contaminated, especially considering that contamination is linked to the conditions related to the hunting, handling and processing of game animals.

Presence of Foodborne Bacteria in Wild Boar and Wild Boar Meat-A Literature Survey for the Period 2012-2022

The wild boar is an abundant game species with high reproduction rates. The management of the wild boar population by hunting contributes to the meat supply and can help to avoid a spillover of transmissible animal diseases to domestic pigs, thus compromising food security. By the same token, wild boar can carry foodborne zoonotic pathogens, impacting food safety. We reviewed literature from 2012-2022 on biological hazards, which are considered in European Union legislation and in international standards on animal health. We identified 15 viral, 10 bacterial, and 5 parasitic agents and selected those nine bacteria that are zoonotic and can be transmitted to humans via food. The prevalence of Campylobacter, Listeria monocytogenes, Salmonella, Shiga toxin-producing E. coli, and Yersinia enterocolitica on muscle surfaces or in muscle tissues of wild boar varied from 0 to ca. 70%. One experimental study reported the transmission and survival of Mycobacterium on wild boar meat. Brucella, Coxiella burnetii, Listeria monocytogenes, and Mycobacteria have been isolated from the liver and spleen. For Brucella, studies stressed the occupational exposure risk, but no indication of meat-borne transmission was evident. Furthermore, the transmission of C. burnetii is most likely via vectors (i.e., ticks). In the absence of more detailed data for the European Union, it is advisable to focus on the efficacy of current game meat inspection and food safety management systems.

Higher Resistance of Yersinia enterocolitica in Comparison to Yersinia pseudotuberculosis to Antibiotics and Cinnamon, Oregano and Thyme Essential Oils

Yersiniosis is an important zoonotic disease; however, data are scarce on the resistance of enteropathogenic yersiniae, especially that of Y. pseudotuberculosis. Minimum inhibitory concentrations (MIC) of 21 antibiotics and 3 essential oils (EOs) were determined by broth microdilution for Y. enterocolitica bioserotype 4/O:3 strains isolated from domestic swine (n = 132) and Y. pseudotuberculosis strains isolated from wild boars (n = 46). For 15 of 21 antibiotics, statistically significant differences were found between MIC values of Y. enterocolitica and Y. pseudotuberculosis. While Y. enterocolitica was more resistant to amoxiclav, ampicillin, cefotaxime, cefuroxime, gentamicin, imipenem, meropenem, tetracycline, tobramycin, and trimethoprim, Y. pseudotuberculosis was more resistant to cefepime, ceftazidime, colistin, erythromycin, and nitrofurantoin. Statistically significant differences were found between various essential oils (p < 0.001) and species (p < 0.001). The lowest MICs for multiresistant Y. enterocolitica (n = 12) and Y. pseudotuberculosis (n = 12) were obtained for cinnamon (median 414 and 207 μg/mL, respectively) and oregano EOs (median 379 and 284 μg/mL), whereas thyme EO showed significantly higher MIC values (median 738 and 553 μg/mL; p < 0.001). There was no difference between Y. enterocolitica strains of plant (1A) and animal (4/O:3) origin (p = 0.855). The results show that Y. enterocolitica is generally more resistant to antimicrobials than Y. pseudotuberculosis.

Different Swine Production Systems Can Shape Slurry Resistome at Mechanism and Class Levels Based on Swine Manure Evaluation

Antimicrobial resistance is a major threat to public health. Antimicrobial use in animal husbandry is a major concern since it can favor an increase in antimicrobial resistance among farms. Herein, we aim to better understand and characterize the main resistome profiles in microbial communities found in pig farms. Sampling of swine manure was performed in two different timepoints (October 2019 and January 2020) in each of the 14 different swine farms, located in the mesoregion of Western Santa Catarina state in Brazil, a pole of swine product production of worldwide importance. Samples were divided into three groups: farms with the opened regimen and no usage of antimicrobials (F1; n = 10), farms with the closed regimen and usage of antimicrobials (F2; n = 16), and farms with the closed regimen and no usage of antimicrobials (F3; n = 2). The metagenomic evaluation was performed to obtain and identify genetic elements related to antimicrobial resistance using nanopore sequencing. We used ResistoXplorer software to perform composition, alpha and beta diversity, and clustering analysis. In addition, PCR reactions were performed to confirm the presence or absence of seven different beta-lactamase family genes and five phosphoethanolamine transferase gene variants clinically relevant. Our findings based on the identification of resistance genes at the mechanism level showed a prevalence of alteration of the drug target (72.3%) profile, followed by drug inactivation (17.5%) and drug efflux (10.1%). We identified predominantly aminoglycosides (45.3%), tetracyclines (15.9%), and multiclass (11,2%) resistance genes. PCoA analysis indicates differences between F1 and F2 profiles. F2 samples showed increased diversity when compared to the F1 group. In addition, herein we first report the identification of mcr-4 in a slurry sample (C1F1.1) in Santa Catarina State. In general, our findings reinforce that many factors on the practices of animal husbandry are involved in the resistome profile at the mechanism and class levels. Further studies to better understand microbiome and mobilome aspects of these elements are necessary to elucidate transmission pathways between different bacteria and environments.

Characterisation of Yersinia enterocolitica strains isolated from wildlife in the northwestern Italian Alps

Introduction

Yersiniosis is a zoonosis causing gastroenteritis, diarrhoea, and occasionally reactive arthritis and septicaemia. Cases are often linked to meat consumption and the most common aetiological agent is the Gram-negative bacilliform Yersinia enterocolitica bacterium. The occurrence of Yersinia spp. among wild animals has mostly been studied in wild boar, but it has seldom been in other species.

Material and Methods

A total of 1,868 faecal samples from animals found dead or hunted were collected between 2015 and 2018 in the Valle d’Aosta region of the northwestern Italian Alps. Alpine ibex faecal samples were collected during a health monitoring program in 2018. Bacteria were isolated via PCR and confirmed as Y. enterocolitica biochemically. Strain antimicrobial susceptibility was tested by Kirby–Bauer disc diffusion, and the presence of virulence factors and antimicrobial resistance genes was investigated using whole-genome sequencing.

Results

Yersinia enterocolitica strains of biotype 1A were detected in six faecal samples from red deer (0.93%), roe deer (0.49%) and red foxes (0.7%). Strains found in beech martens (3.57%) and Alpine ibex (2.77%) belonged to biotypes 1B and 5, respectively and harboured the pYPTS01 plasmid that had only been detected in Y. pseudotuberculosis PB1/+. All the isolates were resistant to ampicillin and erythromycin.

Conclusion

The biovar 1A strains exhibited different virulence factors and behaved like non-pathogenic commensals. The strain from an Alpine ibex also harboured the self-transmissible pYE854 plasmid that can mobilise itself and the pYPTS01 plasmid to other strains. The beech marten could be considered a sentinel animal for Y. enterocolitica. Phenotypic resistance may account for the ability of all the strains to resist β-lactams.

Antibiotic resistance and potential bacterial pathogens identified in red deer's faecal DNA

In the last decades, the wildlife-human interface has been increasing due to several anthropogenic factors. Therefore, it is crucial to be aware of the impact of these new dynamics on the health of wild animals and their associated zoonotic disease risks. This study aimed to characterize the faecal microbiota of two populations of red deer (Cervus elaphus) by metabarcoding, with a particular focus on potential human and veterinary pathogens, and to perform an assessment of antibiotic resistance genes (ARGs) occurrence. The faecal microbiota of red deer was assessed by metabarcoding using the 16S rRNA marker, and OTUs of the genera Treponema, Yersinia, Clostridium, Mycobacterium, and Rickettsia were identified. Two of them affiliated with species more commonly regarded as pathogens (Clostridium piliforme and Yersinia enterocolitica). The quantification of ARGs was performed by quantitative real-time PCR, using a metagenomic approach, and the most abundant genes were found to be bla_TEM , sul1, tetracycline resistance genes (tetW, tetO, and tetQ) and ermF. From these, tetO and tetW are rank II ARGs, which were recently considered future threats for human health. Our results suggest the need for screening programs for the occurrence of pathogens and ARGs in wildlife and particularly in-game species.

Cadmium and wild boar: environmental exposure and immunological impact on macrophages

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Wild boar represents useful bioindicator for Cadmium environmental exposure.

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Cadmium can be absorbed by wild boar moMФ with subsequent cell viability decrease.

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Moderate cadmium concentration down-regulated IL-12p40, TNF-α expression in moMФ.

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Moderate cadmium concentration decreased antimicrobial molecules expression in moMФ.

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Moderate cadmium concentration down-regulated expression of several TLRs in moMФ.

Cadmium (Cd²⁺) is regarded as one of the most toxic heavy metals, which can enter the food chain through environmental contamination and be bioaccumulated. Its exposure in Ligurian wild boars was monitored between 2016–2020 and revealed high level of this heavy metal in different provinces. In one of these polluted area, 21 wild boars were additionally sampled and the relationship between hepatic and renal Cd²⁺ concentration suggested that majority of these animals presented chronic intoxication. Cd²⁺ exposure of wild boar might lead to an immunosuppression status, thus in vitro experiments on wild boar monocyte-derived macrophages (moMФ) were carried out. Effects of Cd²⁺ scalar doses were evaluated through viability and adsorption assays, ELISA, qPCR. Moderate doses of this environmental pollutant (20 μM) were absorbed by moMФ, with subsequent reduction of their viability. This heavy metal did not trigger release of either IFN- β, anti-inflammatory or pro-inflammatory cytokines by moMФ, instead 24 h treatment with 20 μM of Cd²⁺ resulted in down-regulated expression of TNF-α, IL-12p40, several TLRs, CD14, MD2, BD2, MyD88, p65, and NOS2. The results of our monitoring activity suggested that wild boar can be useful to monitor environmental exposure of this heavy metal and can help in understanding the type of contamination. In addition, in vitro experiments on wild boar moMФ revealed that Cd²⁺ exposure negatively affected the immune function of these cells, likely leading to increased susceptibility to infection.

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.

Prevalence and Antimicrobial Resistances of Salmonella spp. Isolated from Wild Boars in Liguria Region, Italy

Salmonella spp. is an important zoonotic agent. Wild boars might host this pathogen in the intestinal tract and might represent a risk for Salmonella spp. transmission to humans. Wild boars are widely spread in Liguria, due to the environmental characteristics of the region. The aim of the study was the isolation, typing, and investigation of antimicrobial susceptibility of the isolated strains of Salmonella spp. During the 2013–2017 hunting seasons, 4335 livers of wild boars were collected and analyzed for the presence of Salmonella spp. A total of 260 strains of Salmonella spp. were isolated and characterized, with a prevalence of 6%. The isolated strains belonged to all six Salmonella enterica subspecies. Most of them were identified as Salmonella enterica subs. enterica of which 31 different serotypes were identified. The dominating serotype identified was S. Enteritidis. The antimicrobial resistance profiles of the isolated strains were analyzed against sixteen molecules. Of the isolated strains, 94.6% were resistant to at least one of the tested antimicrobials. This study showed the circulation of resistant Salmonella spp. strains in the wild boar population living in this area of Italy, underling the potential risk for these animals to disseminate this pathogen and its antimicrobial resistances.