Search Results (34)

The impact of Oedema Disease produced by Shiga toxigenic Escherichia coli (STEC) in swine is increasing in some production countries due to increasing limitations on treatment with antimicrobials and zinc oxide, either because of the increased prevalence of multi-resistant strains or because of legal restrictions. The main pathological effect of Shiga toxin 2e is represented by damage to the endothelial cells of the blood vessel walls, leading to liquid extravasation and oedema formation in multiple tissues. These oedemas are generally easily identifiable in acute clinical cases. However, disease caused by Shiga toxin can occur without any externally visible oedema in the pigs, as observed in the subclinical presentation of Oedema Disease. It also causes productive losses, so it is important to identify and/or diagnose cases to set up control measures in order to optimize production and health. This article includes a comprehensive review of lesions and signs caused by Shiga toxin toxicosis in pigs, as well as other insights about the aetiology and epidemiology of STEC in pigs, and the effect of Shiga toxin recombinant toxoid vaccines in reducing these clinical and subclinical signs under field conditions. Full article

Background/Objectives: Increasing levels of antimicrobial resistance (AMR) have recently been observed at the human–domestic animal–wildlife interface. Wild birds have been identified as carriers of antimicrobial-resistant bacteria and serve as excellent biomarkers for epidemiological studies. This study assessed the current AMR presence in Eastern Spain’s commensal Escherichia coli isolated from free-ranging Bonelli’s eagles (Aquila fasciata). Methods: Nestlings and their nests were intensively sampled between 2022 and 2024 to determine their AMR profile and characterize E. coli. AMR testing was conducted using the broth microdilution method, following the European Committee on Antimicrobial Susceptibility Testing guidelines. Additionally, the presence of eaeA (intimin gene) and stx-1 and stx-2 (shiga toxins) was analyzed by real-time PCR to classify E. coli strains into enteropathogenic (EPEC) and Shiga-toxigenic (STEC) pathotypes. Results: Of all E. coli isolates, 41.7% were resistant to at least one antimicrobial, and 30% were multidrug-resistant. Only two strains were classified as EPEC and none as STEC. The highest resistance rates were observed for amoxicillin and tetracycline (19.6% each). Alarmingly, resistance to colistin and meropenem, last-resort antibiotics in human medicine, was also detected. Conclusions: Although the mechanisms of resistance acquisition remain unclear, transmission is likely to occur through the food chain, with synanthropic prey acting as intermediary vectors. These results highlight the role of Bonelli’s eagles as essential sentinels of environmental AMR dissemination, even in remote ecosystems. Strengthening One Health-based surveillance is necessary to address AMR’s ecological and public health risks in wildlife. Full article

Despite their prevalence in Europe, the source of contamination of humans by Attaching-Effacing Shigatoxigenic Escherichia coli (AE-STEC) O80:H2 remains unidentified. This study aimed to assess a procedure based on non-melibiose fermentation and resistance to tellurite to isolate AE-STEC and enteropathogenic (EPEC) O80:H2 from healthy cattle. The genome sequences of 40 calf and human AE-STEC and EPEC O80:H2 were analyzed: (i) none harbored the mel operon, but the 70mel DNA sequence instead; (ii) the ter-type 1 operon was detected in 16 EPEC and stx1a or stx2a AE-STEC, while no ter-type 1 operon was detected in the remaining 24 EPEC and stx2d AE-STEC. The 21 calf AE-STEC and EPEC O80:H2 were tested phenotypically: (i) none fermented melibiose on melibiose-MacConkey agar plates; (ii) ten of the 11 ter-type 1-positive strains had Minimal Inhibitory Concentrations (MIC) ≥ 128 µg/mL to potassium tellurite; (iii) conversely, the ten ter-negative strains had MIC of two µg/mL. Accordingly, enrichment broths containing two µg/mL of potassium tellurite and inoculated with one high MIC (≥256 µg/mL) stx1a AE-STEC O80:H2 tested positive with the O80 PCR after overnight growth, but not the enrichment broths inoculated with one low MIC (two µg/mL) EPEC. Nevertheless, neither AE-STEC nor EPEC O80:H2 were recovered from 96 rectal fecal samples collected from healthy cattle at one slaughterhouse after overnight growth under the same conditions. In conclusion, this procedure may help to isolate stx1a and stx2a AE-STEC and EPEC O80:H2, but not stx2d AE-STEC that are tellurite sensitive, and new surveys using different procedures are necessary to identify their animal source, if any. Full article

Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen and known to reside naturally in cattle. The application of untreated biological soil amendments of animal origin on fresh produce fields results in unique food safety challenges. It is critical to identify farm manure management practices to mitigate pre-harvest pathogen contamination. The objective of this study was to quantify the prevalence and level of STEC in cattle manure in the Mid-Atlantic region of the United States. A total of 161 bovine manure samples were collected from 13 cattle farms between 2016 and 2018. The samples were enriched with non-selective and selective media and quantified following a Most-Probable Number (MPN) assay. Among the recovered STEC isolates, PCR was performed to determine the presence of stx, eae, and rfbE. Clermont PCR was performed to identify phylogenetic groups of isolates. Of the 13 farms, 11 had STEC populations between <1.0 and >5.6 log MPN/g. Farm, humidity, and sampling year significantly (p < 0.05) influenced STEC populations in bovine manure. Of the 108 isolates, 50% were stx+ and 14% eae+. Phylogenetic group analysis revealed that 46% of the isolates belonged to group A, 19% to B1, 7% to B2, and 28% to D. Group D had the highest prevalence of stx+ and eae+ and group B1 had the lowest prevalence. Results suggest STEC geographical distribution in the Mid-Atlantic region is farm-specific, and climatic conditions can be critical for its survival and dissemination. Full article

Oedema disease (OD) in weaned piglets is caused by shigatoxigenic Escherichia coli (STEC), which produces the Stx2e toxin. The disease is controlled by early vaccination (for example, with Ecoporc Shiga^®). Iron-deficiency anaemia (IDA) and cystoisosporosis are the most common clinical conditions in piglets. These conditions are managed mainly by the intramuscular injection of iron and application of toltrazuril (for example, Forceris^®). In the present study, we sought to evaluate any effect on the efficacy of OD vaccination and iron/anticoccidial treatment resulting from a simultaneous application. An evaluation was carried out by measuring the development of neutralising antibodies against the Stx2e toxin, hematinic indices and oocysts shedding. Six litters from Stx2e-antibody-negative sows were included in the study, with 12 piglets in each litter. The piglets were randomly allocated into two groups on their second day of life (DOL): (T1) iron/anticoccidial treatment and vaccine were administered on different days, and (T2) products were administered simultaneously. Blood samples were collected to determine the levels of serum-neutralising antibodies, haemoglobin and haematocrit. Faecal matter was examined for the presence of oocysts of Cystoisospora suis. No differences were found between the two groups in terms of the development of neutralising antibodies. The levels of haemoglobin and haematocrit were lower (p < 0.05 and p = 0.08, respectively) when iron/anticoccidial treatment and vaccine were applied simultaneously but within the optimal range, based on current interpretive criteria for IDA. Oocysts were not detected in the faecal samples from the animals in either group. In conclusion, we found that, under the conditions of our study, the efficacy of OD vaccination and iron/anticoccidial treatment was not affected by the simultaneous use. Full article

E. coli is considered one of the most important zoonotic pathogens worldwide. Highly virulent and antimicrobial-resistant strains of E. coli have been reported in recent years, making it essential to understand their ecological origins. In this study, we analyzed the characteristics of E. coli strains present in the natural population of American bison (Bison bison) in Mexico. We sampled 123 individuals and determined the presence of E. coli using standard bacteriological methods. The isolated strains were characterized using molecular techniques based on PCR. To evaluate the diversity of E. coli strains in this population, we analyzed 108 suggestive colonies from each fecal sample. From a total of 13,284 suggestive colonies, we isolated 33 E. coli strains that contained at least one virulence gene. The virotypes of these strains were highly varied, including strains with atypical patterns or combinations compared to classical pathotypes, such as the presence of escV, eae, bfpB, and ial genes in E. coli strain LMA-26-6-6, or stx2, eae, and ial genes in E. coli strain LMA-16-1-32. Genotype analysis of these strains revealed a previously undescribed phylogenetic group. Serotyping of all strains showed that serogroups O26 and O22 were the most abundant. Interestingly, strains belonging to these groups exhibited different patterns of virulence genes. Finally, the isolated E. coli strains demonstrated broad resistance to antimicrobials, including various beta-lactam antibiotics. Full article

The emerging heteropathotype shigatoxigenic (STEC) and extra-intestinal pathogenic Escherichia coli (ExPEC) O80:H2 has been the second leading cause of pediatric HUS in France since the mid-2010s. In contrast with other highly pathogenic STEC serotypes, for which ruminants have clearly been identified as the main human infection source, this heteropathotype’s reservoir remains unknown. In this context, we describe for the first time the isolation of seven STEC O80:H2 strains from healthy cattle on a single cattle farm in France. This study aimed at (i) characterizing the genome and (ii) investigating the phylogenetic positions of these O80:H2 STEC strains. The virulomes, resistomes, and phylogenetic positions of the seven bovine isolates were investigated using in silico typing tools, antimicrobial susceptibility testing and cgMLST analysis after short-read whole genome sequencing (WGS). One representative isolate (A13P112V1) was also subjected to long-read sequencing. The seven isolates possessed ExPEC-related virulence genes on a pR444_A-like mosaic plasmid, previously described in strain RDEx444 and known to confer multi-drug resistance. All isolates were clonally related and clustered with human clinical strains from France and Switzerland with a range of locus differences of only one to five. In conclusion, our findings suggest that healthy cattle in France could potentially act as a reservoir of the STEC-ExPEC O80:H2 pathotype. Full article

Shiga toxin-producing Escherichia coli are zoonotic pathogens that cause food-borne human disease. Among these, the O157:H7 serotype has evolved from an enteropathogenic O55:H7 ancestor through the displacement of the somatic gene cluster and recurrent toxigenic conversion by Shiga toxin-converting bacteriophages. However, atypical strains that lack the Shiga toxin, the characteristic virulence hallmark, are circulating in this lineage. For this study, we analyzed the pathogenome and virulence inventories of the stx+ strain, TT12A, isolated from a patient with hemorrhagic colitis, and its respective co-isolated stx− strain, TT12B. Sequencing the genomes to closure proved critical to the cataloguing of subtle strain differentiating sequence and structural polymorphisms at a high-level of phylogenetic accuracy and resolution. Phylogenomic profiling revealed SNP and MLST profiles similar to the near clonal outbreak isolates. Their prophage inventories, however, were notably different. The attenuated atypical non-shigatoxigenic status of TT12B is explained by the absence of both the ΦStx_1a- and ΦStx_2a-prophages carried by TT12A, and we also recorded further alterations in the non-Stx prophage complement. Phenotypic characterization indicated that culture growth was directly impacted by the strains’ distinct lytic phage complement. Altogether, our phylogenomic and phenotypic analyses show that these intimately related isogenic strains are on divergent Stx(+/stx−) evolutionary paths. Full article

Background: Land snails are considered a delicacy in many countries in Europe and sub-Saharan Africa. However, the interaction of microbial pathogens with land snails may present a public health threat when handling and/or consuming snails. This study examines the survival of Escherichia coli in edible land snails in a model system. Methods: Well-studied Shigatoxigenic (STEC) and non-STEC strains were compared. Mature Helix spp. were experimentally fed with E. coli-inoculated oats for 48 h. The snail feces after inoculation were periodically sampled and cultured for a 30-day period and subjected to microbiological analyses. Results: The average rate of decline of the non-STEC strain CSH-62 in the feces of live snails was significantly (p < 0.05) faster than that of STEC ERL 06-2503. In addition, the viable population of E. coli ERL 06-2503 significantly (p < 0.05) persisted for a longer time in the intestine of land snails than E. coli CSH-62. Conclusion: The results showed that the viable population of the E. coli strains examined demonstrated first-order kinetics, and their survival (CFU/mL) appeared significantly (p < 0.05) dependent on the E. coli pathotype. In addition, the continuous enumeration of E. coli in snail faeces indicated that land snails could serve as a mode of transmission of microbial pathogens to susceptible hosts, including humans. Further research is recommended to better quantify the direct and indirect health risks of pathogen transmission by edible snails to humans. Full article

Shiga-toxin-producing Escherichia coli (STEC) is typically detected on food products mainly due to cross-contamination with faecal matter. The serotype O157:H7 has been of major public health concern due to the severity of illness caused, prevalence, and management. In the food chain, the main methods of controlling contamination by foodborne pathogens often involve the application of antimicrobial agents, which are now becoming less efficient. There is a growing need for the development of new approaches to combat these pathogens, especially those that harbour antimicrobial resistant and virulent determinants. Strategies to also limit their presence on food contact surfaces and food matrices are needed to prevent their transmission. Recent studies have revealed that bacteriophages are useful non-antibiotic options for biocontrol of E. coli O157:H7 in both animals and humans. Phage biocontrol can significantly reduce E. coli O157:H7, thereby improving food safety. However, before being certified as potential biocontrol agents, the safety of the phage candidates must be resolved to satisfy regulatory standards, particularly regarding phage resistance, antigenic properties, and toxigenic properties. In this review, we provide a general description of the main virulence elements of E. coli O157:H7 and present detailed reports that support the proposals that phages infecting E. coli O157:H7 are potential biocontrol agents. This paper also outlines the mechanism of E. coli O157:H7 resistance to phages and the safety concerns associated with the use of phages as a biocontrol. Full article

(1) Background: Formation of biofilms on food-contact surfaces by Shiga-toxigenic Escherichia coli (STEC) can pose a significant challenge to the food industry, making conventional control methods insufficient. Targeted use of bacteriophages to disrupt these biofilms could reduce this problem. Previously isolated and characterized bacteriophages (n = 52) were evaluated against STEC biofilms in vitro and on food-contact surfaces. (2) Methods: Phage treatments (9 logs PFU/mL) in phosphate-buffered saline were used individually or as cocktails. Biofilms of STEC (O157, O26, O45, O103, O111, O121, and O145) were formed in 96-well micro-titer plates (7 logs CFU/mL; 24 h) or on stainless steel (SS) and high-density polyethylene (HDPE) coupons (9 logs CFU/cm²; 7 h), followed by phage treatment. Biofilm disruption was measured in vitro at 0, 3, and 6 h as a change in optical density (A₅₉₅). Coupons were treated with STEC serotype-specific phage-cocktails or a 21-phage cocktail (3 phages/serotype) for 0, 3, 6, and 16 h, and surviving STEC populations were enumerated. (3) Results: Of the 52 phages, 77% showed STEC biofilm disruption in vitro. Serotype-specific phage treatments reduced pathogen population within the biofilms by 1.9–4.1 and 2.3–5.6 logs CFU/cm², while the 21-phage cocktail reduced it by 4.0 and 4.8 logs CFU/cm² on SS and HDPE, respectively. (4) Conclusions: Bacteriophages can be used to reduce STEC and their biofilms. Full article

The invasiveness properties of Shigatoxigenic and enteropathogenic Escherichia coli (STEC and EPEC) O80:H2 in humans and calves are encoded by genes located on a pS88-like ColV conjugative plasmid. The main objectives of this study in larvae of the Galleria mellonella moth were therefore to compare the virulence of eight bovine STEC and EPEC O80:H2, of two E. coli pS88 plasmid transconjugant and STX2d phage transductant K12 DH10B, of four E. coli O80:non-H2, and of the laboratory E. coli K12 DH10B strains. Thirty larvae per strain were inoculated in the last proleg with 10 μL of tenfold dilutions of each bacterial culture corresponding to 10 to 10⁶ colony-forming units (CFUs). The larvae were kept at 37 °C and their mortality rate was followed daily for four days. The main results were that: (i) not only the STEC and EPEC O80:H2, but also different E. coli O80:non-H2 were lethal for the larvae at high concentrations (from 10⁴ to 10⁶ CFU) with some variation according to the strain; (ii) the Stx2d toxin and partially the pS88 plasmid were responsible for the lethality caused by the E. coli O80:H2; (iii) the virulence factors of E. coli O80:non-H2 were not identified. The general conclusions are that, although the Galleria mellonella larvae represent a useful first-line model to study the virulence of bacterial pathogens, they are more limited in identifying their actual virulence properties. Full article

The most significant serotype of Shiga-toxigenic Escherichia coli that causes foodborne illnesses is Escherichia coli O157:H7. Elimination of E. coli O157:H7 during food processing and storage is a possible solution. Bacteriophages have a significant impact on bacterial populations in nature due to their ability to lyse their bacterial host. In the current study, a virulent bacteriophage, Ec_MI-02, was isolated from the feces of a wild pigeon in the United Arab Emirates (UAE) for potential future use as a bio-preservative or in phage therapy. Using a spot test and an efficiency of plating analysis, Ec_MI-02 was found to infect in addition to the propagation host, E. coli O157:H7 NCTC 12900, five different serotypes of E. coli O157:H7 (three clinical samples from infected patients, one from contaminated green salad, and one from contaminated ground beef). Based on morphology and genome analysis, Ec_MI-02 belongs to the genus Tequatrovirus under the order Caudovirales. The adsorption rate constant (K) of Ec_MI-02 was found to be 1.55 × 10⁻⁸ mL/min. The latent period was 50 min with a burst size of almost 10 plaque forming units (pfu)/host cell in the one-step growth curve when the phage Ec_MI-02 was cultivated using the propagation host E. coli O157:H7 NCTC 12900. Ec_MI-02 was found to be stable at a wide range of pH, temperature, and commonly used laboratory disinfectants. Its genome is 165,454 bp long with a GC content of 35.5% and encodes 266 protein coding genes. Ec_MI-02 has genes encoding for rI, rII, and rIII lysis inhibition proteins, which supports the observation of delayed lysis in the one-step growth curve. The current study provides additional evidence that wild birds could also be a good natural reservoir for bacteriophages that do not carry antibiotic resistance genes and could be good candidates for phage therapy. In addition, studying the genetic makeup of bacteriophages that infect human pathogens is crucial for ensuring their safe usage in the food industry. Full article

The origin of human and calf infections by Shigatoxigenic (STEC) and enteropathogenic (EPEC) Escherichia coli O80:H2 is still unknown. The aim of this study was to identify E. coli O80 in healthy cattle with an emphasis on melibiose non-fermenting E. coli O80:H2. Faecal materials collected from 149 bulls at 1 slaughterhouse and 194 cows on 9 farms were tested with O80 antigen-encoding gene PCR after overnight growth in enrichment broths. The 53 O80 PCR-positive broths were streaked on different (semi-)selective agar plates. Five E. coli colonies from 3 bulls and 11 from 2 cows tested positive with the O80 PCR, but no melibiose non-fermenting E. coli was isolated. However, these 16 E. coli O80 were negative with PCR targeting the fliC_H2, eae, stx1, stx2 and hlyF genes and were identified by WGS to serotypes and sequence types O80:H6/ST8619 and O80:H45/ST4175. They were phylogenetically related to E. coli O80:H6 and O80:H45 isolated from different animal species in different countries, respectively, but neither to STEC and EPEC O80:H2/ST301, nor to other serotypes of the clonal complex 165. As a conclusion, healthy adult cattle were not identified as a source of contamination of humans and calves by STEC or EPEC O80:H2. Full article

Understanding Shiga toxin subtypes in E. coli from reservoir hosts may give insight into their significance as human pathogens. The data also serve as an epidemiological tool for source tracking. We characterized Shiga toxin subtypes in 491 goat E. coli isolates (STEC) from the mid-Atlantic US region (stx1 = 278, stx2 = 213, and stx1/stx2 = 95). Their serogroups, phylogroups, M13RAPD genotypes, eae (intimin), and hly (hemolysin) genes were also evaluated. STEC-positive for stx1 harbored Stx1c (79%), stx1a (21%), and stx a/c (4%). Those positive for Stx2 harbored stx2a (55%) and Stx2b (32%), while stx2a/stx2d and stx2a/stx2b were each 2%. Among the 343 STEC that were serogrouped, 46% (n = 158) belonged to O8, 20% (n = 67) to 076, 12% (n = 42) to O91, 5% (n = 17) to O5, and 5% (n = 18) to O26. Less than 5% belonged to O78, O87, O146, and O103. The hly and eae genes were detected in 48% and 14% of STEC, respectively. Most belonged to phylogroup B1 (73%), followed by D (10%), E (8%), A (4%), B2 (4%), and F (1%). M13RAPD genotyping revealed clonality of 091, O5, O87, O103, and O78 but higher diversity in the O8, O76, and O26 serogroups. These results indicate goat STEC belonged to important non-O157 STEC serogroups, were genomically diverse, and harbored Shiga toxin subtypes associated with severe human disease. Full article