Characterization of Shiga toxin-producing Escherichia coli from feces of sika deer (Cervus nippon) in Japan using PCR binary typing analysis to evaluate their potential human pathogenicity

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.

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.

Prevalence of Shiga toxin-producing Escherichia coli in Yezo sika deer (Cervus nippon yesoensis) in the Tokachi sub-prefecture of Hokkaido, Japan

In food hygiene, the surveillance of foodborne pathogens in wild animals is indispensable because we cannot control hygienic status of them. Yezo sika deer (Cervus nippon yesoensis), which are found only on the island of Hokkaido, Japan, are the most common game animal in the country. In this study, we analyzed the incidence of Shiga toxin-producing Escherichia coli (STEC) in Yezo sika deer hunted in the Tokachi sub-prefecture, which is one of the densest zones for the sub-species. Real-time polymerase chain reaction testing detected STEC in 18.3% of fecal samples (59/323) collected from deer hunted between 2016 and 2017, whereas no Shigella and Salmonella markers were detected. No correlation was found between STEC detection from fecal samples and characteristics of carcasses, such as hunting area, age, and fascioliasis. From 59 STEC-positive fecal samples, we isolated 37 STEC strains, including 34 O- and H-genotyped strains, in which 16 different serogroups were detected. Genetic analysis revealed that our isolates included various stx gene types (stx1⁺/stx2^-, stx1⁺/stx2⁺, and stx1^-/stx2⁺) and carried eae. This study demonstrated that STEC strains with various features colonized the Yezo sika deer, similar to other subspecies of sika deer. We conclude that continuous surveillance activity is important to monitor the suitability of game animals as a food source and to assess the validity of the food safety management system for game meat production.

Survival of Shiga Toxin-Producing Escherichia coli in Various Wild Animal Feces That May Contaminate Produce

ABSTRACT

Domestic and wild animal intrusions are identified as a food safety risk during fresh produce production. The purpose of this study was to evaluate the survival of Shiga toxin-producing Escherichia coli (STEC) in cattle, feral pig, waterfowl, deer, and raccoon feces from sources in California, Delaware, Florida, and Ohio. Fecal samples were inoculated with a cocktail of rifampin-resistant STEC serotypes (O103, O104, O111, O145, and O157) (104 to 106 CFU/g of feces). Inoculated feces were held at ambient temperature. Populations of surviving cells were monitored throughout 1 year (364 days), with viable populations being enumerated by spread plating and enrichment when the bacteria were no longer detected by plating. Representative colonies were collected at various time intervals based on availability from different locations to determine the persistence of surviving STEC serotypes. Over the 364-day storage period, similar survival trends were observed for each type of animal feces from all states except for cattle and deer feces from Ohio. STEC populations remained the highest in cattle and deer feces from all states between days 28 and 364, except for those from Ohio. Feral pig, waterfowl, and raccoon feces had populations of STEC of <1.0 log CFU/g starting from day 112 in feces from all states. E. coli O103 and O104 were the predominant serotypes throughout the entire storage period in feces from all animals and from all states. The survival of both O157 and non-O157 STEC strains in domesticated and wild animal feces indicates a potential risk of contamination from animal intrusion.

HIGHLIGHTS

PREVALENCE OF YERSINIA AMONG WILD SIKA DEER (CERVUS NIPPON) AND BOARS (SUS SCROFA) IN JAPAN

We examined the prevalence of Yersinia, including pathogenic species such as Yersinia enterocolitica and Yersinia pseudotuberculosis, among wild sika deer (Cervus nippon) and boars (Sus scrofa) captured in Japan. The prevalence of Yersinia in the wild deer was 75% (207/277) and in the boars was 74% (40/54). A total of 417 isolates of nine Yersinia species were isolated from the animals examined: the largest number of isolates (48%, 200/417) were Y. enterocolitica biotype 1A. Pathogenic Y. enterocolitica 1B/O:8 were also isolated from two deer, and Y. pseudotuberculosis serogroups 3 and 4 were isolated from two boars and a deer, respectively. The pathogenic Y. enterocolitica 1B/O:8 isolates carried four virulence genes (ail, ystA, yadA, and virF), and Y. pseudotuberculosis serogroups 3 and 4 isolates carried three virulence genes (inv, yadA, and lcrF). Although the Y. enterocolitica 1B/O:8 and Y. pseudotuberculosis isolates were sensitive to almost all the antimicrobials tested, the two Y. enterocolitica 1B/O:8 isolates were resistant to azithromycin and ampicillin, and the three Y. pseudotuberculosis isolates were resistant only to azithromycin. These findings suggested that wild deer and boars might be important reservoirs for the agent causing human yersiniosis.

Shiga toxin-producing Escherichia coli isolates from red deer (Cervus elaphus), roe deer (Capreolus capreolus) and fallow deer (Dama dama) in Poland

Shiga toxin-producing Escherichia (E.) coli (STEC) pathogens are responsible for the outbreaks of serious diseases in humans, including haemolytic uraemic syndrome (HUS), bloody diarrhoea (BD) and diarrhoea (D), and they pose a significant public health concern. Wild ruminants are an important environmental reservoir of foodborne pathogens that can cause serious illnesses in humans and contaminate fresh products. There is a general scarcity of published data about wildlife as a reservoir of foodborne pathogens in Poland, which is why the potential epidemiological risk associated with red deer, roe deer and fallow deer as reservoirs of STEC/AE-STEC strains was evaluated in this study. The aim of the study was to investigate the prevalence of STEC strains in red deer (Cervus elaphus), roe deer (Capreolus capreolus) and fallow deer (Dama dama) populations in north-eastern Poland, and to evaluate the potential health risk associated with wild ruminants carrying STEC/AE-STEC strains. We examined 252 rectal swabs obtained from 134 roe deer (Capreolus capreolus), 97 red deer (Cervus elaphus) and 21 fallow deer (Dama dama) in north-eastern Poland. The samples were enriched in modified buffered peptone water. Polymerase chain reaction (PCR) assays were conducted to determine the virulence profile of stx1, stx2 and eae or aggR genes, to identify the subtypes of stx1 and stx2 genes, and to perform O and H serotyping. E. coli O157:H7 isolates were detected in the rectal swabs collected from 1/134 roe deer (0.75%) and 4/97 red deer (4.1%), and they were not detected in fallow deer (Dama dama). The remaining E. coli serogroups, namely O26, O103, O111 and O145 that belong to the "top five" non-O157 serogroups, were detected in 15/134 roe deer (11.19%), 18/97 red deer (18.56%) and 2/21 fallow deer (9.52%). STEC/AE-STEC strains were detected in 33 roe deer isolates (24.63%), 21 red deer isolates (21.65%) and 2 fallow deer isolates (9.52%). According to the most recent FAO/WHO report, stx2a and eae genes are the primary virulence traits associated with HUS, and these genes were identified in one roe deer isolate and one red deer isolate. Stx2 was the predominant stx gene, and it was detected in 78.79% of roe deer and in 71.43% of red deer isolates. The results of this study confirmed that red deer and roe deer in north-eastern Poland are carriers of STEC/AE-STEC strains that are potentially pathogenic for humans. This is the first report documenting the virulence of STEC/AE-STEC strains from wild ruminants in Poland.

Isolation and characterisation of Shiga toxin-producing Escherichia coli from Norwegian bivalves

Only a few studies concerning Shiga toxin-producing E. coli (STEC) detection in bivalves and their harvesting areas have been reported, and to the best of our knowledge there are no outbreaks associated with STEC from bivalves described. The aim of the present study was to investigate the occurrence of STEC in Norwegian bivalves, and to characterize potential STEC isolated from the samples. A total of 269 samples of bivalves were screened for the presence of stx and eae genes, and markers for the serogroups O26, O103, O111, O145 and O157 by using ISO TS 13136 (2012). The screening returned 19 samples that were positive for stx and eae, and attempts of isolation of STEC were made from these samples. Presumptive STEC were obtained from three samples, and three isolates (one from each sample) were subjected to whole-genome-sequencing (WGS). The WGS revealed that one of the isolates did not carry the stx genes, while the other two were identified as stx_2i positive E. coli O9:H19 and stx_2g positive E. coli O96:H19. Neither of the two STEC isolates were positive for virulence markers such as eae and ehx. The results suggest that the occurrence of STEC in Norwegian bivalves is low.

Detection of Sarcocystis spp. and Shiga toxin-producing Escherichia coli in Japanese sika deer meat using a loop-mediated isothermal amplification-lateral flow strip

Game meat potentially harbors a number of parasitic and bacterial pathogens that cause foodborne disease. It is thus important to monitor the prevalence of such pathogens in game meats before retail and consumption to ensure consumer safety. In particular, Sarcocystis spp. and Shiga toxin-producing Escherichia coli (STEC) have been reported to be causative agents of food poisoning associated with deer meat consumption. To examine the prevalence of these microbiological agents on-site at a slaughterhouse, the rapid, simple and sensitive detection method known as the “DNA strip” has been developed, a novel tool combining loop-mediated isothermal amplification and a lateral flow strip. This assay has achieved higher sensitivity and faster than conventional PCR and is suitable for on-site inspection.

High flux isothermal assays on pathogenic, virulent and toxic genetics from various pathogens

Toxins, encoding by virulence factors, are significant cause of food-borne illnesses and death in the worldwide. Loop-mediated isothermal amplification (LAMP) is one of the widely used methodologies because of the high sensitivity, specificity and rapidity. Nowadays, LAMP has been regarded as an innovative gene amplification technology and emerged as an alternative to PCR-based methodologies in identification of the pathogenic virulent and toxic genetics. The high sensitivity of LAMP enables detection of the pathogens in sample materials even without time consuming and sample preparation. Therefore, we review the typical characteristics of LAMP assay, recent advance in detection of virulence factors and the application of LAMP assay on detection of four commonly virulence factors. As concluded, with the advantages of rapidity, simplicity, sensitivity, specificity and robustness, LAMP is capable of identification the virulence factors. Moreover, the main purpose of this review is to provide theory support for the application of LAMP assay on the virulence factors identification.