Escherichia coli O157:H7 Infections Associated with Contaminated Pork Products - Alberta, Canada, July-October 2014

Prevalence, Molecular Characterization, and Antimicrobial Resistance Profiles of Shiga Toxin-Producing Escherichia coli Isolated from Raw Beef, Pork, and Chicken Meat in Vietnam

Shiga toxin-producing Escherichia coli (STEC) is one of the most important foodborne pathogens, and the rise of antibiotic resistance to it is a significant threat to global public health. The purpose of this study is to investigate the prevalence, molecular characterization, and antibiotic resistance of STEC isolated from raw meat in Vietnam. The findings in this study showed that the prevalence of STEC in raw beef, pork, and chicken meat was 9.72% (7/72), 5.56% (4/72), and 1.39% (1/72), respectively. The STEC isolates were highly resistant to ampicillin (91.67%) and tetracycline (91.67%), followed by trimethoprim/sulfamethoxazole (83.33%), streptomycin (75%), and florfenicol (66.67%). The incidence of STEC virulence-associated genes, including stx1, stx2, eae, and ehxA, was 8.33% (1/12), 91.67% (11/12), 33.33% (4/12), and 58.33% (7/12), respectively. STEC serogroups O157, O26, and O111 were detected in 3 out of 12 STEC isolates. Two isolates were found to be ESBL producers carrying the blaCTX-M-55 gene, and three isolates were colistin-resistant strains harboring the mcr-1 gene. Notably, a STEC O111 isolate from chicken meat harbored both the blaCTX-M-55 and mcr-1 genes.

Microbiological and chemical analysis of food collected under official control in the Emilia-Romagna region of northern Italy, 2014-2019

This study analyzed data from six years (2014-2019) of official controls in the Emilia-Romagna region (northern Italy) to investigate the frequencies of human pathogens and chemical hazards in foods during production and distribution. Campylobacter spp. was the most prevalent pathogen, isolated in 4.4% of the 1,078 food samples examined, followed by Salmonella spp. (2.8%), Shiga toxin-producing Escherichia coli (STEC) (1.9%) and Listeria monocytogenes (0.9%). Salmonella serotyping showed that the isolates belonged to the serotypes most commonly isolated from humans in Emilia-Romagna. These serotypes were: S. Infantis (34.8%), mostly isolated from chicken, monophasic S. Typhimurium (1,4, (Anonymous, 2013),12:i:-) (12.6%), S. Bredeney (8.9%) and S. Derby (8.6%). No Clostridium botulinum, Yersinia spp. and Shigella spp. were isolated. No positivity was detected for hepatitis A virus, while 5.1% samples taken in the production phase of the food chain were found to be contaminated with norovirus. The chemical analyses identified environmental contaminants within legal limits (heavy metals, 0.6% positive overall; mycotoxins, 0.4% positive overall), analytes subjected to monitoring (perfluoro-alkyl substances (PFASs), 6.2% positive overall; inorganic arsenic, no positives overall) and process contaminants and additives within legal limits (acrylamide, 9.6% positive overall; permitted or non-permitted additives, 0.9% positive overall). Only one sample showed dioxins and polychlorinated biphenyls (PCBs) at levels higher than the legal limits. The monitoring by competent authorities (CA) of food contamination can generate useful data that can be used as a basis for estimating the exposure to different food contaminants over time and for evaluating the effects of control measures on the contamination of food.

Breeding for disease resilience: opportunities to manage polymicrobial challenge and improve commercial performance in the pig industry

Disease resilience, defined as an animal's ability to maintain productive performance in the face of infection, provides opportunities to manage the polymicrobial challenge common in pig production. Disease resilience can deliver a number of benefits, including more sustainable production as well as improved animal health and the potential for reduced antimicrobial use. However, little progress has been made to date in the application of disease resilience in breeding programs due to a number of factors, including (1) confusion around definitions of disease resilience and its component traits disease resistance and tolerance, and (2) the difficulty in characterizing such a complex trait consisting of multiple biological functions and dynamic elements of rates of response and recovery from infection. Accordingly, this review refines the definitions of disease resistance, tolerance, and resilience based on previous studies to help improve the understanding and application of these breeding goals and traits under different scenarios. We also describe and summarize results from a "natural disease challenge model" designed to provide inputs for selection of disease resilience. The next steps for managing polymicrobial challenges faced by the pig industry will include the development of large-scale multi-omics data, new phenotyping technologies, and mathematical and statistical methods adapted to these data. Genome editing to produce pigs resistant to major diseases may complement selection for disease resilience along with continued efforts in the more traditional areas of biosecurity, vaccination and treatment. Altogether genomic approaches provide exciting opportunities for the pig industry to overcome the challenges provided by hard-to-manage diseases as well as new environmental challenges associated with climate change.

Shiga Toxin-Producing Escherichia coli (STEC) and STEC-Associated Virulence Genes in Raw Ground Pork in Canada

ABSTRACT

Shiga toxin-producing Escherichia coli (STEC) O157:H7/nonmotile and some non-O157 STEC strains are foodborne pathogens. In response to pork-associated O157 STEC outbreaks in Canada, we investigated the occurrence of STEC in Canadian retail raw ground pork during the period of 1 November 2014 to 31 March 2016. Isolated STEC strains were characterized to determine the Shiga toxin gene (stx) subtype and the presence of virulence genes encoding intimin (eae) and enterohemorrhagic E. coli hemolysin (hlyA). O157 STEC and non-O157 STEC strains were isolated from 1 (0.11%) of 879 and 13 (2.24%) of 580 pork samples, respectively. STEC virulence gene profiles containing both eae and hlyA were found only in the O157 STEC (stx2a, eae, hlyA) isolate. The eae gene was absent from all non-O157 STEC isolates. Of the 13 non-O157 STEC isolates, two virulence genes of stx1a and hlyA were found in four (30.8%) O91:H14 STEC isolates, whereas one virulence gene of stx2e, stx1a, and stx2a was identified in five (38.5%), two (15.4%), and one (7.7%) STEC isolates, respectively, of various serotypes. The remaining non-O157 STEC isolate carried stx2, but the subtype is unknown because this isolate could not be recovered for sequencing. O91:H14 STEC (stx1a, hlyA) was previously reported in association with diarrheal illnesses, whereas the other non-O157 STEC isolates identified in this study are not known to be associated with severe human illnesses. Virulence gene profiles identified in this study indicate that the occurrence of non-O157 STEC capable of causing severe human illness is rare in Canadian retail pork. However, O157 STEC in ground pork can occasionally occur; therefore, education regarding the potential risks associated with STEC contamination of pork would be beneficial for the public and those in the food industry to help reduce foodborne illnesses.

HIGHLIGHTS

Genomic analysis of Shiga toxin-producing Escherichia coli O157:H7 from cattle and pork-production related environments

Three E. coli O157:H7 outbreaks have been attributed to contaminated pork in Alberta, Canada, recently. This study investigates the phylogenetic relatedness of E. coli O157:H7 from pigs, cattle, and pork-production environments for source attribution. Limited strain diversity was observed using five conventional subtyping methods, with most or all strains being in one subgroup. Whole-genome single nucleotide polymorphism analysis confirmed the recent ancestry of the isolates from all three sources. Most environmental isolates clustered closer with pig isolates than cattle isolates. Also, a direct link was observed between 2018-outbreak environmental isolates and isolates collected from a pig farm in 2018. The majority of pig isolates harbor only one Shiga toxin gene, stx_2a, while 70% (35/50) of the cattle isolates have both stx_1a and stx_2a. The results show some E. coli O157:H7 strains could establish persistence on pig farms and as such, pigs can be a significant source of the organism.

Mucosal IFNγ production and potential role in protection in Escherichia coli O157:H7 vaccinated and challenged cattle

Shiga-toxin producing Escherichia coli O157:H7 (O157)-based vaccines can provide a potential intervention strategy to limit foodborne zoonotic transmission of O157. While the peripheral antibody response to O157 vaccination has been characterized, O157-specific cellular immunity at the rectoanal junction (RAJ), a preferred site for O157 colonization, remains poorly described. Vaccine induced mucosal O157-specific antibodies likely provide some protection, cellular immune responses at the RAJ may also play a role in protection. Distinct lymphoid follicles were increased in the RAJ of vaccinated/challenged animals. Additionally, increased numbers of interferon (IFN)γ-producing cells and γδ + T cells were detected in the follicular region of the RAJ of vaccinated/challenged animals. Likewise, adjuvanted-vaccine formulation is critical in immunogenicity of the O157 parenteral vaccine. Local T cell produced IFNγ may impact epithelial cells, subsequently limiting O157 adherence, which was demonstrated using in vitro attachment assays with bovine epithelial cells. Thus, distinct immune changes induced at the mucosa of vaccinated and challenged animals provide insight of mechanisms associated with limiting O157 fecal shedding. Enhancing mucosal immunity may be critical in the further development of efficacious vaccines for controlling O157 in ruminants and thus limiting O157 transmission to humans.

Genome Sequences of 104 Escherichia coli O157:H7 Isolates from Pigs, Cattle, and Pork Production Environments in Alberta, Canada

Genome sequences of Escherichia coli O157:H7 originating from pigs are limited in the public databases. We sequenced 104 E. coli O157:H7 isolates from pig and cattle feces and pork production environments in Alberta, Canada. The information will aid studies investigating sources of E. coli O157:H7 contaminating pork and the associated environments.

Genome sequences of Escherichia coli O157:H7 originating from pigs are limited in the public databases. We sequenced 104 E. coli O157:H7 isolates from pig and cattle feces and pork production environments in Alberta, Canada. The information will aid studies investigating sources of E. coli O157:H7 contaminating pork and the associated environments.

Survey of Intact and Nonintact Raw Pork Collected at Retail Stores in the Mid-Atlantic Region of the United States for the Seven Regulated Serogroups of Shiga Toxin-Producing Escherichia coli

A total of 514 raw pork samples (395 ground or nonintact and 119 intact samples) were purchased at retail stores in Pennsylvania, Delaware, and New Jersey between July and December 2017. All raw pork samples were screened for serogroup O26, O45, O103, O111, O121, O145, or O157:H7 cells of Shiga toxin-producing Escherichia coli (STEC-7) using standard microbiological and molecular methods. In short, 21 (5.3%) of the 395 ground or nonintact pork samples and 3 (3.4%) of the 119 intact pork samples tested positive via the BAX system real-time PCR assay for the stx and eae virulence genes and for the somatic O antigens for at least one of the STEC-7 serogroups. However, none of these 24 presumptive-positive pork samples subsequently yielded a viable isolate of STEC displaying a STEC-7 serogroup-specific surface antigen in combination with the stx and eae genes. These data suggest that cells of STEC serogroups O26, O45, O103, O111, O121, O145, or O157:H7 are not common in retail raw pork samples in the mid-Atlantic region of the United States.

Epidemiology of Shiga Toxin-Producing Escherichia coli O157 in the Province of Alberta, Canada, 2009-2016

Shiga toxin-producing Escherichia coli (STEC) infections are the product of the interaction between bacteria, phages, animals, humans, and the environment. In the late 1980s, Alberta had one of the highest incidences of STEC infections in North America. Herein, we revisit and contextualize the epidemiology of STEC O157 human infections in Alberta for the period 2009–2016. STEC O157 infections were concentrated in large urban centers, but also in rural areas with high cattle density. Hospitalization was often required when the Shiga toxin genotype stx2a stx2c was involved, however, only those aged 60 years or older and infection during spring months (April to June) independently predicted that need. Since the late 1980s, the rate of STEC O157-associated hemolytic uremic syndrome (HUS) in Alberta has remained unchanged at 5.1%, despite a marked drop in the overall incidence of the infection. While Shiga toxin genotypes stx1a stx2c and stx2a stx2c seemed associated with HUS, only those aged under 10 years and infection during spring months were independently predictive of that complication. The complexity of the current epidemiology of STEC O157 in Alberta highlights the need for a One Health approach for further progress to be made in mitigating STEC morbidity.

Detection and isolation of Shiga Toxin-producing Escherichia coli (STEC) strains in caecal samples from pigs at slaughter in Italy

Shiga toxin-producing Escherichia coli (STEC) strains are food-borne pathogens of public health concern. Despite ruminants are the most important reservoir, STEC human infections have also been attributed to pigs. We examined for the presence of STEC in 234 samples of swine caecal content collected during the year 2015 at Italian abattoirs in the framework of the harmonized monitoring of antimicrobial resistance (Decision 2013/652/EU). The presence of stx genes was detected in 122 (52.1%) samples, which were subsequently subjected to STEC isolation and characterization. The analysis of the 66 isolated STEC strains showed that the majority of the isolates (74.2%) possessed the stx2a gene subtype, in a few cases (16.7%) in combination with stx2b or stx2c. Only 25.8% of isolates possessed the stx2e subtype, typical of swine-adapted STEC. None of the isolates possessed the intimin-coding eae gene and the majority of them did not belong to serogroups commonly associated with human infections. The results of this study suggest that pigs can be considered as potential reservoir of certain STEC types.

Cellular and Mucosal Immune Responses Following Vaccination with Inactivated Mutant of Escherichia coli O157:H7

Shiga toxin-producing Escherichia coli O157:H7 (O157) can cause mild to severe gastrointestinal disease in humans. Cattle are the primary reservoir for O157, which colonizes the intestinal tract without inducing any overt clinical symptoms. Parenteral vaccination can reduce O157 shedding in cattle after challenge and limit zoonotic transmission to humans, although the impact of vaccination and vaccine formulation on cellular and mucosal immune responses are undetermined. To better characterize the cattle immune response to O157 vaccination, cattle were vaccinated with either water-in-oil-adjuvanted, formalin-inactivated hha deletion mutant of Shiga toxin 2 negative (stx2^-) O157 (Adj-Vac); non-adjuvanted (NoAdj-Vac); or non-vaccinated (NoAdj-NoVac) and peripheral T cell and mucosal antibody responses assessed. Cattle in Adj-Vac group had a higher percentage of O157-specific IFNγ producing CD4⁺ and γδ⁺ T cells in recall assays compared to the NoAdj-Vac group. Furthermore, O157-specific IgA levels detected in feces of the Adj-Vac group were significantly lower in NoAdj-Vac group. Extracts prepared only from Adj-Vac group feces blocked O157 adherence to epithelial cells. Taken together, these data suggest parenteral administration of adjuvanted, inactivated whole-cell vaccines for O157 can induce O157-specific cellular and mucosal immune responses that may be an important consideration for a successful vaccination scheme.

Vaccines Against Escherichia coli

Escherichia coli has a complex and versatile nature and continuously evolves from non-virulent isolates to highly pathogenic strains causing severe diseases and outbreaks. Broadly protective vaccines against pathogenic E. coli are not available and the rising in both, multi-drug resistant and hypervirulent isolates, raise concern for healthcare and require continuous efforts in epidemiologic surveillance and disease monitoring. The evolving knowledge on E. coli pathogenesis mechanisms and on the mediated immune response following infection or vaccination, together with advances in the "omics" technologies, is opening new perspectives toward the design and development of effective and innovative E. coli vaccines.

The EspF N-Terminal of Enterohemorrhagic Escherichia coli O157:H7 EDL933w Imparts Stronger Toxicity Effects on HT-29 Cells than the C-Terminal

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 EspF is an important multifunctional protein that destroys the tight junctions of intestinal epithelial cells and promotes host cell apoptosis. However, its molecular mechanism remains elusive. We knocked out the espF sequence (747 bp, ΔespF), N-terminal sequence (219 bp, ΔespF_N), and C-terminal sequence (528 bp, ΔespF_C) separately using the pKD46-mediated λ Red homologous recombination system. Then, we built the corresponding complementation strains, namely, ΔespF/pespF, ΔespF_N/pespF_N, and ΔespF_C/pespF_C by overlap PCR, which were used in infecting HT-29 cells and BALB/C mice. The level of reactive oxygen species, cell apoptosis, mitochondrial trans-membrane potential, inflammatory factors, transepithelial electrical resistance (TER), and animal mortality were evaluated by DCFH-DA, double staining of Annexin V-FITC/PI, JC-1 staining, ELISA kit, and a mouse assay. The wild-type (WT), ΔespF, ΔespF/pespF, ΔespF_C, ΔespF_C/pespF_C, ΔespF_N, and ΔespF_N/pespF_N groups exhibited apoptotic rates of 68.3, 27.9, 64.9, 65.7, 73.4, 41.3, and 35.3% respectively, and mean TNF-α expression levels of 428 pg/mL, 342, 466, 446, 381, 383, and 374 pg/mL, respectively. In addition, the apoptotic rates and TNF-α levels of the WT, ΔespF/pespF, and ΔespF_C were significantly higher than that of ΔespF, ΔespF_N, ΔespF_C/pespF_C, and ΔespF_N/pespF_N group (p < 0.05). The N-terminal of EspF resulted in an increase in the number of apoptotic cells, TNF-α secretion, ROS generation, mitochondria apoptosis, and pathogenicity in BalB/c mice. In conclusion, the N-terminal domain of the Enterohemorrhagic E. coli O157:H7 EspF more strongly promotes apoptosis and inflammation than the C-terminal domain.

Shiga Toxin-Producing Escherichia Coii in Slaughtered Pigs and Pork Products

During the years 2015-2016, 83 faecal samples were collected at slaughter from pigs reared in farms located in Central-Northern Italy. During the years 2014-2016 a total of 562 pork products [465 not-readyto-eat (NRTE) and 97 ready-to-eat (RTE) products] were collected from retail outlets, large retailers and processing plants. The samples were analysed according to ISO TS 13136:2012. Out of 83 swine faecal samples, 77 (92.8%) resulted stx-positive by real time polymerase chain reaction (PCR), 5 stx2+ and 1 stx1+ Shiga toxin-producing Escherichia coli (STEC) strains were isolated. Among the 465 NRTE samples, 65 (14.0%) resulted stx-positive by real time PCR and 7 stx2+ STEC strains were isolated. The stx2 gene was detected more frequently than the stx1 gene both in faecal samples (90.4 vs 8.4%) and in NRTE pork products (13.3 vs 1.3%). All the RTE samples included in the analysis resulted stx-negative. Among the samples resulted positive for stx and eae genes, serogroup-associated genes were detected at high frequency: O26 resulted the most frequent in faecal samples (81.3%) and O145 in pork products (88.1%). The O157 serogroup resulted positive in 83.3 and 78.1% of pork products and faecal samples, respectively. Despite the frequent detection by real time PCR of genes indicating the possible presence of STEC strains belonging to the six serogroups, the bacteriological step did not confirm the isolation of any such strains.