Phenotypic and genotypic characterization of beta-D-glucuronidase-positive Shiga toxin-producing Escherichia coli O157:H7 isolates from deer

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.

First isolation of verocytotoxin-producing Escherichia coli O157:H7 from sports animals in Southern Thailand

Background and Aim:

Escherichia coli O157:H7 is enterohemorrhagic E. coli, which produces verocytotoxin or Shiga toxin. It is a well-known cause of severe diseases in humans worldwide. Cattle and other ruminants are the main reservoirs of this organism. Sports animals, such as fighting bulls, riding horses, and fighting cocks, are economic animals in Southern Thailand. This study aimed to identify E. coli O157:H7 from the rectal swabs of these sports animals and determine the antimicrobial susceptibility patterns of isolated bacteria.

Materials and Methods:

The rectal swabs were collected from 34 fighting bulls, 32 riding horses, and 31 fighting cocks. The swabs were cultured on MacConkey (MAC) Agar; the suspected colonies were then identified by VITEK^® 2 GN card, and the antimicrobial susceptibility was tested by VITEK^® 2 AST N194 in VITEK^® 2 Compact automation. Escherichia coli O157:H7 was confirmed by culturing on sorbitol MAC agar, the ability to grow at 44°C, and the presence of H7 antigen. In addition, the eaeA (E. coli attaching and effacing), along with stx1 and stx2 (Shiga cytotoxins) genes, were determined using polymerase chain reaction. Finally, the cytotoxicity of Shiga toxin was confirmed using the Vero cytotoxicity test.

Results:

Fifty-five suspected isolates (56.70%), which were collected from 19 fighting bulls (55.88%), 13 riding horses (40.63%), and 23 fighting cocks (71.13%), were identified as E. coli. However, one sample (Bull H9/1) from fighting bulls had an equal confidence level (50%) for E. coli and E. coli O157. The confirmation of this isolate demonstrated that it was sorbitol non-fermenter, could assimilate L-lactate, was unable to grow well at 44°C, and reacted with anti-serum to H7 antigen. In addition, it was positive with stx2 and eaeA genes, and the toxin affected Vero cells by a dose-dependent response. The antimicrobial susceptibility test revealed that five out of 55 (9.09%) E. coli isolates were resistant to antimicrobial agents. All five isolates (21.74%) were collected from fighting cocks. Escherichia coli Cock H4/3 was only one of the five isolates resistant to three antimicrobial agents (ciprofloxacin, moxifloxacin, and trimethoprim/sulfamethoxazole). Fortunately, it was not multidrug-resistant bacteria.

Conclusion:

This is the first report on detection of E. coli O157:H7 in fighting bulls and antibiotic-resistant characteristic of E. coli in fighting cocks in Southern Thailand. This research is beneficial in preventing the dissemination of E. coli O157:H7 or antimicrobial agent-resistant E. coli in sports animals and humans.

Whole-genome sequence analysis of Shiga toxin-producing Escherichia coli O157 strains isolated from wild deer and boar in Japan

The prevalence of Shiga toxin-producing Escherichia coli O157 (STEC O157) strains in wild deer and boar in Japan was investigated. STEC O157 strains were isolated from 1.9% (9/474) of the wild deer and 0.7% (3/426) of the wild boar examined. Pulsed-field gel electrophoresis (PFGE) analysis classified the wild deer and boar strains into four and three PFGE patterns, respectively. The PFGE pattern of one wild boar strain was similar to that of a cattle strain that had been isolated from a farm in the same area the wild boar was caught, suggesting that a STEC O157 strain may have been transmitted between wild boar and cattle. Clade analysis indicated that, although most of the strains were classified in clade 12, two strains were classified in clade 7. Whole-genome sequence (WGS) analysis indicated that all the strains carried mdfA, a drug resistance gene for macrolide antibiotics, and also pathogenicity-related genes similar to those in the Sakai strain. In conclusion, our study emphasized the importance of food hygiene in processing meat from Japanese wild animals for human consumption.

Game Meat Consumption and Foodborne Illness in Japan: A Web-Based Questionnaire Survey

HIGHLIGHTS

Game meat represents a unique source of foodborne illness in humans. A Web-based survey about game meat consumption was completed by 50,000 respondents. The odds of illness were greater among consumers of raw game meat than processed meat. The greater the number of game meat types consumed, the higher the prevalence of illness. Those who hunted and prepared bear, boar, and deer meat were likely to get ill.

Genomic Characterization of β-Glucuronidase-Positive Escherichia coli O157:H7 Producing Stx2a

Among Shiga toxin (Stx)–producing Escherichia coli (STEC) O157:H7 strains, those producing Stx2a cause more severe diseases. Atypical STEC O157:H7 strains showing a β-glucuronidase–positive phenotype (GP STEC O157:H7) have rarely been isolated from humans, mostly from persons with asymptomatic or mild infections; Stx2a-producing strains have not been reported. We isolated, from a patient with bloody diarrhea, a GP STEC O157:H7 strain (PV15-279) that produces Stx2a in addition to Stx1a and Stx2c. Genomic comparison with other STEC O157 strains revealed that PV15-279 recently emerged from the stx1a/stx2c-positive GP STEC O157:H7 clone circulating in Japan. Major virulence genes are shared between typical (β-glucuronidase–negative) and GP STEC O157:H7 strains, and the Stx2-producing ability of PV15-279 is comparable to that of typical STEC O157:H7 strains; therefore, PV15-279 presents a virulence potential similar to that of typical STEC O157:H7. This study reveals the importance of GP O157:H7 as a source of highly pathogenic STEC clones.

A Review of Zoonotic Infection Risks Associated with the Wild Meat Trade in Malaysia

The overhunting of wildlife for food and commercial gain presents a major threat to biodiversity in tropical forests and poses health risks to humans from contact with wild animals. Using a recent survey of wildlife offered at wild meat markets in Malaysia as a basis, we review the literature to determine the potential zoonotic infection risks from hunting, butchering and consuming the species offered. We also determine which taxa potentially host the highest number of pathogens and discuss the significant disease risks from traded wildlife, considering how cultural practices influence zoonotic transmission. We identify 51 zoonotic pathogens (16 viruses, 19 bacteria and 16 parasites) potentially hosted by wildlife and describe the human health risks. The Suidae and the Cervidae families potentially host the highest number of pathogens. We conclude that there are substantial gaps in our knowledge of zoonotic pathogens and recommend performing microbial food safety risk assessments to assess the hazards of wild meat consumption. Overall, there may be considerable zoonotic risks to people involved in the hunting, butchering or consumption of wild meat in Southeast Asia, and these should be considered in public health strategies.

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

This study examined the potential pathogenicity of Shiga toxin-producing Escherichia coli (STEC) in feces of sika deer by PCR binary typing (P-BIT), using 24 selected STEC genes. A total of 31 STEC strains derived from sika deer in 6 prefectures of Japan were O-serotyped and found to be O93 (n=12), O146 (n=5), O176 (n=3), O130 (n=3), O5 (n=2), O7 (n=1), O96 (n=1), O116 (n=1), O141 (n=1), O157 (n=1) and O-untypable (n=1). Of the 31 STEC strains, 13 carried both stx1 and stx2, 5 carried only stx1, and 13 carried one or two variants of stx2. However, no Stx2 production was observed in 3 strains that carried only stx2: the other 28 strains produced the appropriate Stx. P-BIT analysis showed that the 5 O5 strains from two wild deer formed a cluster with human STEC strains, suggesting that the profiles of the presence of the 24 P-BIT genes in the deer strains were significantly similar to those in human strains. All of the other non-O157 STEC strains in this study were classified with strains from food, domestic animals and humans in another cluster. Good sanitary conditions should be used for deer meat processing to avoid STEC contamination, because STEC is prevalent in deer and deer may be a potential source of STEC causing human infections.

Genotypic and phenotypic characterization of antimicrobial-resistant Escherichia coli from farm-raised diarrheic sika deer in Northeastern China

In China, overuse and/or abuse of antimicrobials are common in stockbreeding, which possess high risks of antimicrobial-resistant contaminations. The serogroups, major virulence genes, and antimicrobial resistant patterns of the antimicrobial-resistant Escherichia coli (E. coli) were investigated in the feces of diarrheic farm-raised sika deer from 50 farms in three Northeastern provinces of China. A total of 220 E. coli isolates were obtained and characterized. Twenty-eight O serogroups were identified from the obtained E. coli isolates with O2, O26, O128, O142 and O154 being dominant. Nearly all the isolates were resistant to at least four of the tested antimicrobials. More than 90% of the E. coli isolates carried at least one of the tested virulence genes. About 85% of the E. coli isolates carried one or more antimicrobial-resistant genes responsible for resistant phenotypes of sulfonamides, streptomycin/spectionomycin or tetracycline. The antimicrobial resistant level and pathogenic group occurrences of the obtained E. coli isolates were higher than that of livestock and wild animals reported in some developed countries. Thus, the fecal-carrying antimicrobial-resistant E. coli from the farm-raised sika deer is potentially a significant contamination source for freshwater systems and food chain, and may pose great health risks for human and animals in Northeastern China.

Prevalence, distribution and evolutionary significance of the IS629 insertion element in the stepwise emergence of Escherichia coli O157:H7

Background

Insertion elements (IS) are known to play an important role in the evolution and genomic diversification of Escherichia coli O157:H7 lineages. In particular, IS629 has been found in multiple copies in the E. coli O157:H7 genome and is one of the most prevalent IS in this serotype. It was recently shown that the lack of O157 antigen expression in two O rough E. coli O157:H7 strains was due to IS629 insertions at 2 different locations in the gne gene that is essential for the O antigen biosynthesis.

Results

The comparison of 4 E. coli O157:H7 genome and plasmid sequences showed numerous IS629 insertion sites, although not uniformly distributed among strains. Comparison of IS629s found in O157:H7 and O55:H7 showed the presence of at least three different IS629 sub-types. O157:H7 strains carry IS629 elements sub-type I and III whereby the ancestral O55:H7 carries sub-type II. Analysis of strains selected from various clonal groups defined on the E. coli O157:H7 stepwise evolution model showed that IS629 was not observed in sorbitol fermenting O157 (SFO157) clones that are on a divergent pathway in the emergence of O157:H7. This suggests that the absence of IS629 in SFO157 strains probably occurred during the divergence of this lineage, albeit it remains uncertain if it contributed, in part, to their divergence from other closely related strains.

Conclusions

The highly variable genomic locations of IS629 in O157:H7 strains of the A6 clonal complex indicates that this insertion element probably played an important role in genome plasticity and in the divergence of O157:H7 lineages.

Detection of Escherichia coli O157:H7 virulence genes in isolates from beef, pork, water, human and animal species in the northwest province, South Africa: public health implications

The aim of the present study was to isolate and identify Escherichia coli O157:H7 from pigs, cattle, humans, beef, pork and water samples and to determine their putative virulence genes by PCR analysis. A total of 220 samples were analysed; 5600 presumptive E. coli O157:H7 were screened for the presence of rfb(O157) and fliC(H7) gene fragments by PCR and 130 isolates were confirmed. The prevalence of E. coli O157:H7 was higher in pigs and pork 88(67.7%) than in cattle and beef 36(27.7%), water 3(2.3%) or humans 1 (0.77%). Moreover, the pathogen was more frequently isolated from faecal (16.9%-43.1%) than from meat samples (10.8%-24.6%). A large proportion--73 (56.2%)--of the isolates possessed the hlyA gene, while 48 (36.9%) harboured the eaeA gene. Although there were no major differences in the number of isolates harbouring the stx(1) and stx(2) genes, respectively, only a small proportion 13(10%) harboured both shiga toxin genes. Despite this, the proportion of isolates that possessed the stx(1) 29(22.3%) was higher than those possessing the stx(2) gene. None of the E. coli O157:H7 isolates harboured all four shiga-toxin producing E. coli (STEC) virulence genes investigated. When comparing the proportion of isolates obtained from the different sample sources and/or stations, significant positive correlations were observed between isolates from Mafikeng and Lichtenburg (r = 0.981, p < 0.05) and those from Mafikeng and Rustenburg (r = 0.991, p < 0.05). These results therefore indicate that meat and faeces samples obtained from major cities in the northwest province were contaminated with E. coli O157:H7. We suggest that there is a need for improving the sanitary conditions of farms, abattoirs and butcher shops. This could reduce transmission of E. coli O157:H7 to humans.

Assessment of Shiga toxin-producing Escherichia coli isolates from wildlife meat as potential pathogens for humans

A total of 140 Shiga toxin-producing Escherichia coli (STEC) strains from wildlife meat (deer, wild boar, and hare) isolated in Germany between 1998 and 2006 were characterized with respect to their serotypes and virulence markers associated with human pathogenicity. The strains grouped into 38 serotypes, but eight O groups (21, 146, 128, 113, 22, 88, 6, and 91) and four H types (21, 28, 2, and 8) accounted for 71.4% and 75.7% of all STEC strains from game, respectively. Eighteen of the serotypes, including enterohemorrhagic E. coli (EHEC) O26:[H11] and O103:H2, were previously found to be associated with human illness. Genes linked to high-level virulence for humans (stx(2), stx(2d), and eae) were present in 46 (32.8%) STEC strains from game. Fifty-four STEC isolates from game belonged to serotypes which are frequently found in human patients (O103:H2, O26:H11, O113:H21, O91:H21, O128:H2, O146:H21, and O146:H28). These 54 STEC isolates were compared with 101 STEC isolates belonging to the same serotypes isolated from farm animals, from their food products, and from human patients. Within a given serotype, most STEC strains were similar with respect to their stx genotypes and other virulence attributes, regardless of origin. The 155 STEC strains were analyzed for genetic similarity by XbaI pulsed-field gel electrophoresis. O103:H2, O26:H11, O113:H21, O128:H2, and O146:H28 STEC isolates from game were 85 to 100% similar to STEC isolates of the same strains from human patients. By multilocus sequence typing, game EHEC O103:H2 strains were attributed to a clonal lineage associated with hemorrhagic diseases in humans. The results from our study indicate that game animals represent a reservoir for and a potential source of human pathogenic STEC and EHEC strains.

Genetic diversity among clonal lineages within Escherichia coli O157:H7 stepwise evolutionary model

Molecular characterization and subtyping show genetic diversities within clonal complexes.

Escherichia coli O157:H7 variants were examined for trait mutations and by molecular subtyping to better define clonal complexes postulated on the O157:H7 evolution model. Strains of β-glucuronidase–positive, sorbitol-negative O157:H7 isolated in United States and Japan were identical to A5 clonal strain and shared sequence type (ST)–65 by multilocus sequence typing (MLST); thus, they belong in A5. However, these strains exhibited pulsed-field gel electrophoresis (PFGE) profile differences that suggested genomic divergence between populations. Sorbitol-fermenting O157 (SFO157) strains from Finland, Scotland, and Germany were identical to A4 clonal strain and belong in A4. Some SFO157 strains, isolated years apart and from different countries, had identical PFGE profiles, suggesting a common origin. Despite similarities, some Finnish and Scottish and all of the German strains have ST-75 (“German clone”), whereas others have ST-76, a new variant (“Scottish clone”). MLST of strains in other clonal complexes also discriminated strains thought to be identical and showed that genetic differences will further distinguish clonal populations into subclones.

Presence of Shiga toxin-producing E. coli O157:H7 in a survey of wild artiodactyls

This study was carried out to evaluate the role of wild artiodactyls as reservoirs of Escherichia coli O157:H7 for livestock and humans. Retroanal mucosal swabs samples from 206 red deer (Cervus elaphus), 20 roe deer (Capreolus capreolus), 6 fallow deer (Dama dama) and 11 mouflon (Ovis musimon), collected during the hunting season (autumn-winter) in South-western Spain, were screened. Samples were pre-enriched in modified buffered peptone water, concentrated by an immunomagnetic separation technique and cultured onto selective cefixime tellurite sorbitol MacConkey agar. Polymerase chain reaction (PCR) was used to detect the presence of genes coding O157 and H7 antigens and the virulence factors verocytotoxin, intimin and enterohaemolysin. Three E. coli O157:H7 isolates were obtained from red deer (1.5%). Two of them showed inability to ferment sorbitol and lack of beta-d-glucuronidase (GUD) activity, however, the other strain investigated was an atypical sorbitol-fermenting E. coli O157:H7 with GUD(+) activity. This is the first report pointing to red deer as a reservoir of E. coli O157:H7 in Spain.