Safety Properties of Escherichia coli O157:H7 Specific Bacteriophages: Recent Advances for Food Safety

Prevalence, identification of virulence genes, and antibiotic resistance properties of Shiga-toxin producing Escherichia coli (STEC) strains isolated from ice cream and juice in sales centers

OBJECTIVE

Contaminated food with Shiga-toxin producing Escherichia coli (STEC) can cause diarrhea and severe diseases in consumers. This study aimed to assess the phenotypic and genotypic characteristics of virulence and antibiotic resistance genes in STEC strains isolated from various types of ice cream and fruit juice sold in Isfahan, Iran.

METHODS

From March 2023 to March 2024, 500 samples-including traditional ice cream (100), industrial ice cream (100), frozen ice cream (100), traditional juice (100), and industrial juice (100)-were collected. Samples were analyzed using biochemical and molecular methods for STEC detection. Antibiotic sensitivity was evaluated using the disc diffusion method against 14 antibiotics. Specific primers were used to identify antibiotic resistance and virulence genes.

RESULTS

Among the 500 samples, 52 (10.42%) were E. coli positive, with the highest prevalence found in traditional juice (20%) and traditional ice cream (15%). The pathogenic subtype, particularly enterohemorrhagic E. coli (EHEC), was most common in traditional juice (75% of positive samples) and traditional ice cream (66.66%). High antibiotic resistance rates were observed against ampicillin (86.53%), tetracycline (76.92%), and sulfamethoxazole (73.07%), while the lowest resistance was recorded for imipenem (7.69%). The most frequently detected antibiotic resistance genes were aadA1 (76.92%), tetA (57.69%), and sul1 (55.76%). Key virulence genes included stx1, stx2, and eaeA.

CONCLUSION

These findings emphasize the public health risks associated with STEC contamination in food products and the need for stricter food safety measures and antibiotic stewardship programs. These findings highlight the public health risks of STEC contamination in food products, particularly traditional ice cream and juice. Localized studies are essential to understand specific risks and inform targeted interventions. Strategies such as improved hygiene practices, stringent food safety regulations, and effective antibiotic stewardship programs are critical to mitigating the threat posed by STEC in food products.

Unraveling the Resistome, Virulome, and Pathogenicity of Escherichia Coli O157:H7 From Cattle Feces

Antimicrobial-resistant Escherichia coli, especially those belonging to the serotype O157, are increasingly linked to foodborne diseases with significant fatality rates worldwide. The food and medical industries have focused on E. coli O157:H7 due to its ability to produce toxins coupled with its low infectious dose. The aim of this study was to assess the virulome, resistome, and pathogenicity of E. coli O157:H7 using whole genome sequencing. Three previously isolated E. coli O157:H7 strains from cattle feces were subjected to whole genome sequencing. The genome sizes of all three E. coli O157:H7 strains were 5,117,276 bp, 5,039,443 bp, and 5,034,351 bp. The C + G contents were 50.22%, 50.53%, and 50.54%, while the number of contigs was 110, 43, and 42, respectively, for E. coli O157:H7 strains J32, J57, and J69. Several virulence determinants (hemorrhagic E. coli pilus (HCP), eaeA, hemolysin, etc.) were found in the genomes of these isolates. In addition, antibiotic resistance genes conferring resistance to aminoglycosides, tetracyclines, macrolides, fluoroquinolones, penams, carbapenems, cephalosporins, cephamycin, rifamycin, phenicols, monobactams, and nitroimidazole were found in the genomes. Interestingly, the genomes of these isolates also harbored determinants encoding resistance to disinfectants and antiseptics, indicating their concern in the food production and medical sectors. This highlights the public health concerns of these isolates, indicating the need for constant surveillance.

Molecular characterization and safety properties of multi drug-resistant Escherichia coli O157:H7 bacteriophages

The increase in multi drug resistance (MDR) amongst food-borne pathogens such as Escherichia coli O157:H7, coupled with the upsurge of food-borne infections caused by these pathogens is a major public health concern. Lytic phages have been employed as an alternative to antibiotics for use against food-borne pathogens. However, for effective application, phages should be selectively toxic. Therefore, the objective of this study was to characterise lytic E. coli O157:H7 phages isolated from wastewater as possible biocontrol agents and access their genomes for the absence of genes that denotes virulence, resistance, toxins, and lysogeny using whole genome sequencing. E. coli O157:H7 bacteriophages showed clear plaques ranging in size from 1.0 mm to 2.0 mm. Spot test and Efficiency of plating (EOP) analysis demonstrated that isolated phages could infect various environmental E. coli strains. Four phages; vB_EcoM_EP32a, vB_EcoP_EP32b, vB_EcoM_EP57, and vB_EcoM_EP69 demonstrated broad lytic spectra against E. coli O157:H7 strains. Transmission Electron Microscopy (TEM) showed that all phages have tails and were classified as Caudoviricetes. Growth parameters showed an average latent period of 15 ± 3.8 min, with a maximum burst size of 392 PFU/cell. The phages were stable at three distinct temperatures (4 °C, 28 °C, and 37 °C) and at pH values of 3.5, 5.0, 7.0, 9.0, and 11.0. Based on their morphological distinctiveness, three phages were included in the Whole Genome Sequencing (WGS) analysis. WGS results revealed that E. coli O157:H7 phages (vB_EcoM_EP32a, vB_EcoP_EP32b, and vB_EcoM_EP57) were composed of linear double-stranded DNA (dsDNA) with genome sizes 163,906, 156,698, and 130,723 bp and GC contents of 37.61, 37, and 39% respectively. Phages vB_EcoM_EP32a and vB_EcoP_EP32b genomes were classified under the class Caudoviricetes, Straboviridae family, and the new genus "Phapecoctavirus", while vB_EcoM_EP57 was classified under the class Caudoviricetes, Autographiviridae family. Genome analysis revealed no lysogenic (integrase), virulence, or antimicrobial resistance sequences in all three Escherichia phage genomes. The overall results provided evidence that lytic E. coli O157:H7 bacteriophages in this study, are relatively stable, can infect diverse E. coli strains, and does not contain genes responsible for virulence, resistance, toxins, and lysogeny. Thus, they can be considered as biocontrol candidates against MDR pathogenic E. coli O157:H7 strains in the food industry.

Combating antibiotic resistance in a one health context: a plethora of frontiers

One of the most significant medical advancements of the 20th century was the discovery of antibiotics, which continue to play a vital tool in the treatment and prevention of diseases in humans and animals. However, the imprudent use of antibiotics in all fields of One-Health and concerns about antibiotic resistance among bacterial pathogens have raised interest in antibiotic use restrictions on a global scale. Despite the failure of conventional antimicrobial agents, only about 15 new antibiotics have been introduced clinically since year 2000 to date. Moreover, there has been reports of resistance to some of these new antibiotics. This has necessitated a need to search for alternative strategies to combat antimicrobial resistant pathogens. Thus, this review compiles and evaluates the approaches-natural compounds, phage treatment, and nanomaterials-that are being used and/or suggested as the potential substitutes for conventional antibiotics.

An integrated magnetic separation enzyme-linked colorimetric sensing platform for field detection of Escherichia coli O157: H7 in food

An intelligent colorimetric sensing platform integrated with in situ immunomagnetic separation function was developed for ultrasensitive detection of Escherichia coli O157: H7 (E. coli O157: H7) in food. Captured antibody modified magnetic nanoparticles (cMNPs) and detection antibody/horseradish peroxidase (HRP) co-functionalized AuNPs (dHAuNPs) were firstly synthesized for targeted enrichment and colorimetric assay of E. coli O157: H7, in which remarkable signal amplification was realized by loading large amounts of HRP on the surface of AuNPs. Coupling with the optical collimation attachments and embedded magnetic separation module, a highly integrated optical device was constructed, by which in situ magnetic separation and high-quality imaging of 96-well microplates containing E. coli O157: H7 was achieved with a smartphone. The concentration of E. coli O157: H7 could be achieved in one-step by performing digital image colorimetric analysis of the obtained image with a custom-designed app. This biosensor possesses high sensitivity (1.63 CFU/mL), short detecting time (3 h), and good anti-interference performance even in real-sample testing. Overall, the developed method is expected to be a novel field detection platform for foodborne pathogens in water and food as well as for the diagnosis of infections due to its portability, ease of operation, and high feasibility.

An Emerging Foodborne Pathogen Spotlight: A Bibliometric Analysis and Scholarly Review of Escherichia coli O157 Research

Foodborne infections pose a substantial global threat, causing an estimated 600 million illnesses and resulting in approximately 420,000 deaths annually. Among the diverse array of pathogens implicated in these infections, Escherichia coli (E. coli), specifically the O157 strain (E. coli O157), emerges as a prominent pathogen associated with severe outbreaks. This study employs a comprehensive bibliometric analysis and scholarly review focused on E. coli O157 research. The bibliometric analysis highlights the significant role played by the United States in the E. coli O157 research domain. Further exploration underscores the noteworthy contributions of the researcher Doyle MP, whose body of work, consisting of 84 documents and an impressive H-Index of 49, reflects their substantial impact in the field. Recent research trends indicate a discernible shift towards innovative detection methods, exemplified by the adoption of CRISPR-CAS and Loop-Mediated Isothermal Amplification. Moreover, high-throughput whole-genome sequencing techniques are gaining prominence for the expeditious analysis of pathogenic E. coli strains. Scientists are increasingly exploring antimicrobial agents, including phage therapy, to address the challenges posed by antibiotic-resistant E. coli strains, thereby addressing critical concerns related to multi-drug resistance. This comprehensive analysis provides vital insights into the dynamic landscape of E. coli O157 research. It serves as a valuable resource for researchers, policymakers, and healthcare professionals dedicated to mitigating E. coli O157 outbreaks and advancing global public health strategies.