Pathogenicity of Shiga toxin-producing Escherichia coli (STEC) from wildlife: Should we care?

Risk for public health of multiresistant Shiga toxin-producing Escherichia coli (STEC) in wild boar (Sus scrofa) in Tunisia

BACKGROUND

Wild boar (Sus scrofa) is increasingly implicated as a reservoir of various pathogens, such as Shiga toxin-producing E. coli (STEC) that are transmissible to other wildlife, domestic animals and humans. This represents risks to both human and animal health by causing food-borne infections. This investigation set out to evaluate the antibiotic resistance profiles and virulence factor rates of STEC strains isolated from wild boars.

MATERIAL AND METHODS

A total of 110 fecal samples were taken from postmortem carcasses of wild boar that were collected during the hunting campaign. PCR was used to check for the presence of the STEC virulence genes stx1, while stx2, eaeA, and ehxA in E. coli isolates. The detection of STEC serogroups was carried out by PCR amplification. Additional virulence genes, phylogenetic groups and integrons were determined in the STEC strains. Antibiotic resistance was assessed in the isolates against 21 antimicrobial agents by disk-diffusion method.

RESULTS

STEC isolates were identified in 10.9 % (12/110) of the E. coli isolates and the serogroups were O157, O145, O45 and O26. Of the strains, 75 % contained the Shiga toxin-1 gene (stx1), stx2 and ehxA were identified in 66.7 % and 33.3 % respectively. Other virulence factors fimH, traT, iutA, cdt3, ibeA, aer and fyuA were found in 100 %, 50 %, 41.7 %, 41.7 %, 33.3 %, 25 % and 8.3 % of the strains, respectively. Integrons classes 1 and 2 were found in 58.3 % and 8.3 % of the strains, respectively. The majority of STEC isolates belonged to phylogroup B1 (58.4 %), followed by E (25 %), A (8.3 %), and D (8.3 %).

CONCLUSIONS

Our findings suggest that wild boars are an important reservoir of STEC isolates. Based on the presence of virulence factors encoding for toxins (stx1 and stx2), adhesins, and invasion among STEC strains in association with integrons as mobile genetic elements, these strains may have a high potential to cause human disease.

Making sense of sentinels: wildlife as the One Health bridge for environmental antimicrobial resistance surveillance

Antimicrobial resistance (AMR), arising from decades of imprudent anthropogenic use of antimicrobials in healthcare and agriculture, is considered one of the greatest One Health crises facing healthcare globally. Antimicrobial pollutants released from human-associated sources are intensifying resistance evolution in the environment. Due to various ecological factors, wildlife interact with these polluted ecosystems, acquiring resistant bacteria and genes. Although wildlife are recognized reservoirs and disseminators of AMR in the environment, current AMR surveillance systems still primarily focus on clinical and agricultural settings, neglecting this environmental dimension. Wildlife can serve as valuable sentinels of AMR in the environment, reflecting ecosystem health, and the effectiveness of mitigation strategies. This review explores knowledge gaps surrounding the ecological factors influencing AMR acquisition and dissemination in wildlife, and highlights limitations in current surveillance systems and policy instruments that do not sufficiently address the environmental component of AMR. We discuss the underutilized opportunity of using wildlife as sentinel species in a holistic, One Health-centred AMR surveillance system. By better integrating wildlife into systematic AMR surveillance and policy, and leveraging advances in high-throughput technologies, we can track and predict resistance evolution, assess the ecological impacts, and better understand the complex dynamics of environmental transmission of AMR across ecosystems.

Systematic Review of the Occurrence and Antimicrobial Resistance Profile of Foodborne Pathogens from Enterobacteriaceae in Wild Ungulates Within the European Countries

Game meat is derived from non-domesticated, free-ranging wild animals and plays an important role in human nutrition, but it is recognized as a source of food-borne and drug-resistant pathogens impacting food safety. The present review aimed to provide a comprehensive analysis of the frequency of isolation and antimicrobial resistance (AMR) profiles of major foodborne pathogens from the Enterobacteriaceae, including Salmonella, Escherichia, and Yersinia genera, in wild ungulates, across Europe in the 21st century. A systematic search was conducted via the Google Scholar database using the PRISMA guidelines. In this regard, the content of a total of 52 relevant scientific publications from both European Union (n = 10) and non-European Union countries (n = 3) was processed, highlighting the main scientific achievements and indicating knowledge gaps and future perspectives. The studies highlighted that Salmonella spp. was the most commonly encountered pathogen, and significant AMR levels were noticed for the isolated strains, especially against penicillin (32.8%) and amoxicillin (32.1%). This review underscores the importance of monitoring the presence of food-borne pathogens and their AMR in wildlife as important public health and food safety concerns.

Shiga Toxin-Producing Escherichia coli Isolated from Wild Ruminants in Liguria, North-West Italy

Wildlife may represent an important source of infectious diseases for humans and other wild and domestic animals. Wild ruminants can harbour and transmit Shiga toxin-producing Escherichia coli (STEC) to humans, and some strains even carry important antimicrobial resistance. In this study, 289 livers of wild roe deer, fallow deer, red deer and chamois collected in Liguria, north-west Italy, from 2019 to 2023 were analysed. Overall, 44 STEC strains were isolated from 28 samples. The characterisation of serogroups showed the presence of O104, O113, O145 and O146 serogroups, although for 28 colonies, the serogroup could not be determined. The most prevalent Shiga toxin gene in isolated strains was Stx2, and more specifically the subtype Stx2b. The other retrieved subtypes were Stx1a, Stx1c, Stx1d and Stx2g. The isolated strains generally proved to be susceptible to the tested antimicrobials. However, multi-drug resistances against highly critical antimicrobials were found in one strain isolated from a roe deer. This study highlights the importance of wildlife monitoring in the context of a "One Health" approach.

Hunting Dynamics and Identification of Potentially Pathogenic Bacteria in European Fallow Deer (Dama dama) across Three Hunting Reserves in Western Romania

The study focused on the hunting practices and potentially pathogenic bacterial species among European fallow deer (Dama dama). Within a five-year period, three hunting grounds from Western Romania were examined. During this period, a total of 1881 deer were hunted, and 240 samples were collected by rectal and nasal swabbing from 120 carcasses. Bacterial strains were identified utilizing bacteriological assays and the Vitek® 2 Compact system. Notably, the Socodor hunting ground exhibited a significant difference in harvesting quotas between the bucks (Group M) and does/yearlings (Group F), favoring the latter. In the Chișineu Criș-Sălișteanca hunting ground, a likely correlation in harvesting quotas between the two groups was observed. The identified potentially pathogenic bacteria were Escherichia coli, Salmonella spp., Staphylococcus aureus, Listeria monocytogenes and Enterococcus faecium. These results highlight the importance of effectively managing the deer population and recognize the potential for Dama dama to spread zoonotic pathogens, emphasizing the necessity of adopting a One Health approach and maintaining ongoing surveillance of this game species' population dynamics.

A Comprehensive Review on Shiga Toxin Subtypes and Their Niche-Related Distribution Characteristics in Shiga-Toxin-Producing E. coli and Other Bacterial Hosts

Shiga toxin (Stx), the main virulence factor of Shiga-toxin-producing E. coli (STEC), was first discovered in Shigella dysenteriae strains. While several other bacterial species have since been reported to produce Stx, STEC poses the most significant risk to human health due to its widespread prevalence across various animal hosts that have close contact with human populations. Based on its biochemical and molecular characteristics, Shiga toxin can be grouped into two types, Stx1 and Stx2, among which a variety of variants and subtypes have been identified in various bacteria and host species. Interestingly, the different Stx subtypes appear to vary in their host distribution characteristics and in the severity of diseases that they are associated with. As such, this review provides a comprehensive overview on the bacterial species that have been recorded to possess stx genes to date, with a specific focus on the various Stx subtype variants discovered in STEC, their prevalence in certain host species, and their disease-related characteristics. This review provides a better understanding of the Stx subtypes and highlights the need for rapid and accurate approaches to toxin subtyping for the proper evaluation of the health risks associated with Shiga-toxin-related bacterial food contamination and human infections.

Clinical and public health implications of increasing notifications of LEE-negative Shiga toxin-producing Escherichia coli in England, 2014-2022

Introduction. Shiga toxin-producing Escherichia coli (STEC) belong to a diverse group of gastrointestinal pathogens. The pathogenic potential of STEC is enhanced by the presence of the pathogenicity island called the Locus of Enterocyte Effacement (LEE), including the intimin encoding gene eae.Gap statement. STEC serotypes O128:H2 (Clonal Complex [CC]25), O91:H14 (CC33), and O146:H21 (CC442) are consistently in the top five STEC serotypes isolated from patients reporting gastrointestinal symptoms in England. However, they are eae/LEE-negative and perceived to be a low risk to public health, and we know little about their microbiology and epidemiology.Aim. We analysed clinical outcomes and genome sequencing data linked to patients infected with LEE-negative STEC belonging to CC25 (O128:H2, O21:H2), CC33 (O91:H14) and, and CC442 (O146:H21, O174:H21) in England to assess the risk to public health.Results. There was an almost ten-fold increase between 2014 and 2022 in the detection of all STEC belonging to CC25, CC33 and CC442 (2014 n=38, 2022 n=336), and a total of 1417 cases. There was a higher proportion of female cases (55-70 %) and more adults than children, with patients aged between 20-40 and >70 most at risk across the different serotypes. Symptoms were consistent across the three dominant serotypes O91:H14 (CC33), O146:H21 (CC442) and O128:H2 (CC25) (diarrhoea >75 %; bloody diarrhoea 25-32 %; abdominal pain 64-72 %; nausea 37-45 %; vomiting 10-24 %; and fever 27-30 %). Phylogenetic analyses revealed multiple events of acquisition and loss of different stx-encoding prophage. Additional putative virulence genes were identified including iha, agn43 and subA.Conclusions. Continued monitoring and surveillance of LEE-negative STEC infections is essential due to the increasing burden of infectious intestinal disease, and the risk that highly pathogenic strains may emerge following acquisition of the Shiga toxin subtypes associated with the most severe clinical outcomes.

Comparative evaluation of antimicrobial activity of human granulysin, bovine and porcine NK-lysins against Shiga toxin-producing Escherichia coli O157:H7

Shiga toxin-producing Escherichia coli (STEC) O157:H7 (O157) is a foodborne pathogen causing human disease ranging from hemorrhagic colitis and hemolytic uremic syndrome to kidney failure, while remaining harmless to cattle, its primary reservoir. The severity of the human disease associated mainly with Shiga toxin production and a global emergence of antibiotic resistant STEC highlights the need for effective non-antibiotic, pre-harvest strategies to reduce O157 in cattle, the principal source of human infection. Towards this goal three synthetic antimicrobial peptides (AMPs): human granulysin (hGRNL), bovine NK-lysin (bNK2A), and porcine NK-lysin (pNKL), were tested in vitro against O157 isolates. As expected, circular dichroism spectroscopy findings were consistent with a predominantly α-helical conformation for all three AMPs in an environment mimicking bacterial outer surface or liposaccharides. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations of hGRNL (200 μM), bNK2A (12.5 μM against strain 86-24 and 25 μM against EDL933), and pNKL (6.25 μM) were determined using the Clinical and Laboratory Standards Institute broth microdilution method in Müeller-Hinton broth (cation-adjusted). The bNK2A and pNKL AMPs did not induce Shiga toxin expression in O157 at MIC, as there was a significant decrease or no change in toxin expression following 4- or 20 h incubation with the AMPs; bNK2A p <0.0001 (4 h) and p = 0.4831 (20 h); pNKL p <0.0001 (4 h) and p = 0.0001 (20 h). Propidium iodide uptake assay revealed faster O157 membrane damage or killing kinetics with bNK2A and pNKL compared to hGRNL. Nonetheless, transmission electron microscopy demonstrated that all three AMPs mediated damage to O157 membranes. In contrast, the three AMPs showed minimal cytotoxicity (<2%) against cattle red blood cells at tested concentrations (0.39-50 μM). Overall, our results demonstrate the potential for bNK2A and pNKL to be further developed into novel non-antibiotic agents to reduce O157 shedding in cattle.

Prevalence of Shiga Toxin-Producing Escherichia coli O157 in Wild Scottish Deer with High Human Pathogenic Potential

Shiga toxin-producing E. coli (STEC) infections associated with wildlife are increasing globally, highlighting many 'spillover' species as important reservoirs for these zoonotic pathogens. A human outbreak of STEC serogroup O157 in 2015 in Scotland, associated with the consumption of venison meat products, highlighted several knowledge gaps, including the prevalence of STEC O157 in Scottish wild deer and the potential risk to humans from wild deer isolates. In this study, we undertook a nationwide survey of wild deer in Scotland and determined that the prevalence of STEC O157 in wild deer is low 0.28% (95% confidence interval = 0.06-0.80). Despite the low prevalence of STEC O157 in Scottish wild deer, identified isolates were present in deer faeces at high levels (>104 colony forming units/g faeces) and had high human pathogenic potential based on whole genome sequencing and virulence gene profiling. A retrospective epidemiological investigation also identified one wild deer isolate from this study as a possible source of a Scottish human outbreak in 2017. These results emphasise the importance of food hygiene practices during the processing of wild deer carcasses for human consumption.

Physicochemical, microbiological, and sensory characteristics of "Sui Wu'u" traditional pork products from Bajawa, West Flores, Indonesia

Background and Aim

Sui Wu'u is a traditional meat preservation product from Bajawa, a region in East Nusa Tenggara. It is made by mixing pork with salt and corn flour, which is then stored in a bamboo container (tuku) for months. After 6 months of storage, this study examined the physicochemical, microbiological, and sensory properties of Sui Wu'u.

Materials and Methods

Sui Wu'u products were prepared using the traditional recipe from the Bajawa community. Fresh pork (pork belly and backfat), corn flour, and salt were purchased from local/traditional markets at proportions of 65%, 30%, and 5%, respectively. The physicochemical, amino acid, fatty acid profile, microbiological, and sensory properties of Sui Wu'u were evaluated after being stored for 6 months in a bamboo container (tuku).

Results

The results indicated that these Sui Wu'u were mainly characterized by high-fat levels, followed by protein. The pH value, salt content, moisture content, and water activity were 4.72%, 1.72%, 6.11%, and 0.62%, respectively. Minerals (K, P, Se, and Zn) and vitamin B6, as well as amino acids, such as leucine, phenylalanine, lysine (essential amino acids), glycine, proline, glutamic acid, and alanine (non-essential amino acids), are present in Sui Wu'u. The fatty acid profile was dominated by monounsaturated fatty acids (MUFA) (21.69%), saturated fatty acids (SFA) (17.78%), and polyunsaturated fatty acids (PUFA) (5.36%). Monounsaturated fatty acids, oleic acid (C18:1n9) was the most abundant fatty acid in Sui Wu'u, followed by palmitic acid SFA (C16:0); MUFA stearic acid (C18:0); and PUFA linoleic (C18:2n-6). The microbiological characteristics of Sui Wu'u showed no detectable microorganisms (<10 CFU/g) for Salmonella, total E. coli and total Staphylococcus, and average values of 4.4 × 105 CFU/g for total microbes, which were still below the maximum limit of microbial contamination according to the regulations of the Food and Drug Supervisory Agency of the Republic of Indonesia. The sensory assessment indicated that panelists highly preferred (rated as very like) Sui Wu'u for all sensory attributes.

Conclusion

The physicochemical, microbiological, and sensory characteristics of Sui Wu'u after 6 months of storage indicated that it still provides essential nutrients for the body and is quite safe for consumption. The stability of Sui Wu'u's shelf life can be attributed to the appropriate combination of pork, salt, corn flour, bamboo packaging (tuku), and storage temperature. The high-fat content in Sui Wu'u can be reduced by increasing the proportion of lean meat. Ensuring strict sanitation during the manufacturing process, using high-quality pork, salt, corn flour, and proper packaging with bamboo can further improve the safety of Sui Wu'u for consumption.

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.

Shiga Toxin-Producing Escherichia coli in Faecal Samples from Wild Ruminants

Wildlife can harbour Shiga toxin-producing Escherichia coli (STEC). In the present study, STEC in faecal samples from red deer (n = 106) and roe deer (n = 95) were characterised. All isolates were non-O157 strains. In red deer, STEC were detected in 17.9% (n = 19) of the isolates, and the eae/stx_2b virulence profile was detected in two isolates (10.5%). One STEC strain harboured stx_1a (5.3%) and eighteen STEC strains harboured stx₂ (94.7%). The most prevalent stx₂ subtypes were stx_2b (n = 12; 66.7%), stx_2a (n = 3; 16.7%), and stx_2g (n = 2; 11.1%). One isolate could not be subtyped (NS) with the applied primers (5.6%). The most widely identified serotypes were O146:H28 (n = 4; 21%), O146:HNM (n = 2; 10.5%), O103:H7 (n = 1; 5.3%), O103:H21 (n = 1; 5.3%), and O45:HNM (n = 1; 5.3%). In roe deer, STEC were detected in 16.8% (n = 16) of the isolates, and the eae/stx_2b virulence profile was detected in one isolate (6.3%). Two STEC strains harboured stx_1a (12.5%), one strain harboured stx_1NS/stx_2b (6.3%), and thirteen strains harboured stx₂ (81.3%). The most common subtypes were stx_2b (n = 8; 61.5%), stx_2g (n = 2; 15.4%), non-typeable subtypes (NS) (n = 2; 15.4%), and stx_2a (n = 1; 7.7%). Serotype O146:H28 (n = 5; 31.3%) was identified. The study demonstrated that the zoonotic potential of STEC strains isolated from wildlife faeces should be monitored in the context of the 'One Health' approach which links human health with animal and environmental health.

Prevalence and Implications of Shiga Toxin-Producing E. coli in Farm and Wild Ruminants

Shiga-toxin-producing Escherichia coli (STEC) is a food-borne pathogen that causes human gastrointestinal infections across the globe, leading to kidney failure or even death in severe cases. E. coli are commensal members of humans and animals' (cattle, bison, and pigs) guts, however, may acquire Shiga-toxin-encoded phages. This acquisition or colonization by STEC may lead to dysbiosis in the intestinal microbial community of the host. Wildlife and livestock animals can be asymptomatically colonized by STEC, leading to pathogen shedding and transmission. Furthermore, there has been a steady uptick in new STEC variants representing various serotypes. These, along with hybrids of other pathogenic E. coli (UPEC and ExPEC), are of serious concern, especially when they possess enhanced antimicrobial resistance, biofilm formation, etc. Recent studies have reported these in the livestock and food industry with minimal focus on wildlife. Disturbed natural habitats and changing climates are increasingly creating wildlife reservoirs of these pathogens, leading to a rise in zoonotic infections. Therefore, this review comprehensively surveyed studies on STEC prevalence in livestock and wildlife hosts. We further present important microbial and environmental factors contributing to STEC spread as well as infections. Finally, we delve into potential strategies for limiting STEC shedding and transmission.

Virulence Genes of Pathogenic Escherichia coli in Wild Red Foxes (Vulpes vulpes)

Simple Summary

Escherichia coli is a commensal of the intestinal tract of humans and animals, but some pathotypes can cause severe infections. Enteropathogenic E. coli (EPEC), Shiga toxin-producing E. coli (STEC), and enterohemorrhagic E. coli (EHEC) are the pathotypes most frequently involved in enteric disorders observed in people and domestic animals. Wildlife may harbor and excrete these pathotypes too, therefore, they may be source of infections for humans and domestic animals. Vulpes vulpes seem to be involved in the epidemiology of pathogenic E. coli strains, and thus they could be a relevant threat mainly when they invade human settlements in rural and urban areas.

Abstract

Different pathotypes of Escherichia coli can cause severe diseases in animals and humans. Wildlife may contribute to the circulation of pathogenic pathotypes, including enteropathogenic E. coli (EPEC), Shiga toxin-producing E. coli (STEC), and enterohemorrhagic E. coli (EHEC). This study analyzed 109 DNA samples previously extracted from fecal specimens collected from red foxes (Vulpes vulpes) to detect E. coli virulence genes eaeA, hlyA, stx1, and stx2, that characterize the EPEC, STEC, and EHEC strains. Thirty-one (28.4%) samples were positive for at least one investigated virulence gene: eaeA gene was detected in 21 (19.2%) samples, hlyA in 10 (9.1%), stx1 in 6 (5.5%), and stx2 in 4 (3.6%). Nine DNA samples resulted positive for two or three virulence genes: five (4.6%) samples were positive for eaeA and hlyA genes, two (1.8%) for eaeA and stx1, one (0.9%) for hlyA and stx1, one (0.9%) for eaeA, hlyA and stx2. Red foxes seem to be involved in the epidemiology of these infections and their role could be relevant because they may be source of pathogenic E. coli for other wild animals, as well as domestic animals and humans.