Coli O157 Research Articles

Real-time fluorescence growth curves for viable bacteria quantification in foods

Here, for the first time, we used a membrane permeable fluorescent nucleic acid stain (SYBR Green) to trace the in-vivo DNA replication during bacterial binary fission. Such stain did not influence the growth of bacteria. Nor did the bacteria degrade the stain, enabling the fluorescent microplate reader to monitor sensitively the growth of the bacteria. Hence, a real-time fluorescence growth curve (RTFGC) method was put forward for the sensitive quantification of viable bacteria in foods. Using E. coli O157:H7 as a bacteria model, the RTFGC method could quantify bacteria within the range of 10 to 1 × 106 cfu/mL, with a linear correlation coefficient R2 of 0.997. It was found that melting curve was unique for a particular bacterial strain, which could be used for contamination identifications. Good practicability of the RTFGC in quantifying E. coli O157:H7 from tap water, juices, and milks was demonstrated.

Escherichia coli in betel leaves: prevalence, virulence characterization and antibiogram

Escherichia coli is a significant foodborne pathogen, frequently linked to hemorrhagic diarrhea, especially in developing nations, where it presents considerable public health concerns. This study was conducted to examine the virulence gene profiles and antibiotic resistance patterns of E. coli strains isolated from piper betel leaves. A total of 100 betel leaf samples, including fresh (n = 60) and ready-to-eat (n = 40) specimens, were collected and tested for the presence of E. coli using standard diagnostic techniques, such as selective culture methods, staining, latex agglutination, and polymerase chain reaction (PCR) assays. Further, the identified E. coli isolates underwent PCR-based testing for virulence genes and disk diffusion assays to assess antibiotic susceptibility. Among the 100 samples screened, 4% (n = 4/100; 95% CI: 1.57–9.84; P = 0.1126) were identified as E. coli O157, and 33% (n = 33/100; 95% CI: 24.56–42.69; P = 0.4011) were classified as non-O157 isolates. The virulence gene stx1 was found in 10.81% of isolates, while stx2, eaeA, and hlyA genes were not detected in any samples. Antibiotic resistance analysis showed that all isolates (100%, 37/37) were resistant to amoxicillin and erythromycin, with 75.68% (28/37) demonstrating resistance to tetracycline. Notably, all isolates were fully susceptible to ceftriaxone and ciprofloxacin. A majority (72.97%, 27/37) of isolates were sensitive to streptomycin, and 67.57% (25/37) were sensitive to gentamicin. Additionally, 86.48% of the E. coli isolates exhibited multidrug resistance (MDR), showing 10 resistance patterns, including 8 MDR patterns. The most common MDR pattern was AMX-TE-E, observed in 56.76% (21/37) of isolates. One isolate demonstrated resistance to six of the eight tested antibiotics across four distinct classes, with the resistance pattern AMX-TE-GEN-S-E-AZM. The MAR indices for E. coli isolates ranged between 0.25 and 0.75. These findings highlight the significant threat posed to global public health by multidrug-resistant shiga toxin-producing E. coli found on piper betel leaves in urban environments. Asian Australas. J. Biosci. Biotechnol. 2024, 9(3), 33-44

Investigating the Synergistic Effects of Carvacrol and Citral-Edible Polysaccharide-Based Nanoemulgels on Shelf Life Extension of Chalkidiki Green Table Olives.

Modern bioeconomy and sustainability demands lead food technology in the development of novel biobased edible food preservatives. Herein, the development and characterization of novel polysaccharide (xanthan gum and kappa-carrageenan)-based nanoemulgels (NGs) enhanced with essential oil derivatives; pure citral (CT); pure carvacrol (CV); and various CT:CV ratios (25:75, 50:50, and 75:25) are presented. The obtained NGs are applied as active edible coatings for extending the shelf life of Protected Designation of Origin (PDO) green table olives of Chalkidiki. The zeta potential demonstrated the high stability of the treatments, while light scattering measurement and scanning electron microscopy images confirmed the <100 nm droplet size. EC50 indicated high antioxidant activity for all the tested samples. The fractional inhibitory concentration (FIC) confirmed the synergistic effect of NG with a CT:CV ratio at 50:50 against Staphylococcus aureus and at CT:CV ratios 25:75 and 75:25 against E. coli O157:H7. NG coatings with CT:CV ratios at 50:50 and at 25:75 effectively controlled the weight loss at 0.5%, maintained stable pH levels, and preserved the visual quality of green olives on day 21. The synergistic effect between CT and CV was confirmed as they reduced the spoilage microorganisms of yeasts and molds by 2-log [CFU/g] compared to the control and almost 1 log [CFU/g] difference from pure CT and CV-based NGs without affecting the growth of beneficial lactic acid bacteria crucial for fermentation. NGs with CT:CV ratios at 50:50 and at 25:75 demonstrated superior effectiveness in preventing discoloration and maintaining the main sensory attributes. Overall, shelf life extension was achieved in 21 compared to only 7 of the uncoated ones. Finally, this study demonstrates the potential of polysaccharide-based NGs in mixtures of CT and CV for the shelf life extension of fermented food products.

Biocontrol of Salmonella Schwarzengrund and Escherichia coli O157:H7 planktonic and biofilm cells via combined treatment of polyvalent phage and sodium hexametaphosphate on foods and food contact surfaces

Salmonella Schwarzengrund and Escherichia coli O157:H7 are ones of foodborne pathogens that can produce biofilms and cause serious food poisoning. Bacteriophages are an emerging antibacterial strategy used to prevent foodborne pathogen contamination in the food industry. In this study, the combined antibacterial effects of the polyvalent phage PS5 and sodium hexametaphosphate (SHMP) against both pathogens were investigated to evaluate their effectiveness in food applications. The combined treatment with phage PS5 (multiplicity of infection, MOI = 10) and 1.0% SHMP inhibited the growth of S. Schwarzengrund and E. coli O157:H7, and the viable counts of both decreased by more than 2.45 log CFU/mL. In KAGOME vegetable and fruit mixed juice, the combined treatment with PS5 (MOI = 100) and 1.0% SHMP also resulted in significant pathogen inactivation at 4 °C after 24 h. PS5 (1010 PFU/mL) and 1.0% SHMP showed stronger synergistic effects on biofilm formation and the removal of established biofilms on polystyrene plates. Additionally, we evaluated their combined effects on reducing the biofilms of S. Schwarzengrund and E. coli O157:H7 on glass tubes and cabbage leaves at 4 °C. These findings indicate the utility of this approach in the biocontrol of the planktonic and biofilm cells of S. Schwarzengrund and E. coli O157:H7 on foods and food contact surfaces.

Integration of MALDI glycotyping and NMR analysis to uncover an O-antigen substructure from pathogenic Escherichia coli O111

Escherichia coli O111 is a critical pathogenic E. coli serotype that causes severe, potentially fatal complications. Despite its reported variation, only one structure of the O-antigen polysaccharide from E. coli O111 has been reported. Here, a substructure of the O-antigen from E. coli O111 was characterized using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and NMR analysis. MALDI glycotyping revealed differing O-antigen repeating unit masses of Δm/z 787 and 828 in the E. coli strains and lipopolysaccharides from the O111 serogroup. This variation was caused by the replacement of the hexose residue with hexosamine in the repeating units, which was further confirmed by LIFT-TOF/TOF analysis. Structural elucidation of the O111 substructure by NMR analysis further demonstrated replacement of the hydroxyl group with an N-acetyl group on the terminal glucose residue of the O-antigen pentasaccharide repeating unit. To our knowledge, this study is the first to provide a detailed structural analysis of a new O-antigen substructure from the E. coli O111 serogroup.

Antibacterial effects and mechanisms of quercetin-β-cyclodextrin complex mediated photodynamic on Escherichia coli O157:H7.

Quercetin is a natural flavonoid with antioxidant, anti-inflammatory, and antibacterial properties. This work aimed to formulate quercetin-cyclodextrin microcapsules (QT-β-CD) while examining their photodynamic antibacterial effects and underlying mechanisms in detail. Characterization of the QT-β-CD was conducted using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The bacteriostatic effects of UV-A irradiation on Escherichia coli O157:H7 (E. coli O157:H7) were investigated. The photodynamic impact of QT-β-CD was assessed by analyzing hydrogen peroxide (H₂O₂) production. The antimicrobial activity was further elucidated through examinations of cell membrane integrity, protein damage, changes in cellular motility, biofilm formation, and extracellular polysaccharide reduction. The effect of QT-β-CD on LuxS and motA gene expression in E. coli O157:H7 was investigated by RT-qPCR. The findings demonstrated that QT-β-CD exhibited potent photodynamic properties and functioned as an efficient photosensitizer, causing substantial damage to E. coli O157:H7 cells. These results underscore the potential of quercetin as an antimicrobial agent for food preservation.

Ten-year comparison of the efficiency of legal regulations of foodborne pathogens in broilers in Türkiye

Broiler meats are the primary source of foodborne pathogens, such as Campylobacter jejuni and Salmonella spp., and E. coli O157. The illegal use of antibiotics for preventive purposes or the habit of using broad-spectrum antibiotics in farms causes antibiotic resistance in these pathogens. This study compared C. jejuni, Salmonella spp. and E. coli O157 and their antibiotic resistance patterns in broiler meats in 2011-2012 and 2021-2022. The research we conducted in 2011-2012 to observe the effectiveness of the legal regulations enacted in Türkiye in 2014 and 2018 for controlling pathogens and monitoring the use of antibiotics was also repeated with a similar sample set in 2021-2022. The results showed the prevalence of C. jejuni, Salmonella spp., and E. coli O157 in 2011-2012 and 2021-2022 with 68.0%, 30.4%, 0.8% and 10.08%, 7.77%, 0.21%, respectively. The antimicrobial susceptibility tests against gentamicin, streptomycin, erythromycin, ciprofloxacin, enrofloxacin, tetracycline and oxytetracycline were performed by agar disk diffusion method. According to results in 2011-2012, all C. jejuni and Salmonella spp. were resistant to at least one tested antibiotic, with 31.57% Salmonella spp. and 16.47% C. jejuni being multidrug-resistant. In addition, one of the E. coli O157 strains was resistant to one antibiotic, and the other was resistant to two antibiotics. In 2021-2022, 81.3% C. jejuni, 46% Salmonella spp., and only one E. coli O157 were resistant to at least one tested antibiotic. Isolated strains of 8.33% C. jejuni and 21.62% Salmonella spp. were multidrug-resistant. In the past, antibiotics were used for preventative purposes, as indicated by the survey results. Today, it is evident that these rates have decreased to low levels as a result of legal regulations and monitoring.

Feeding Cows with Olive Cake Enriched in Polyphenols Improves the Sustainability and Enhances the Nutritional and Organoleptic Features of Fresh Caciocavallo Cheese.

In this study, Caciocavallo, a typical cheese produced in Sicily Island (Italy), was obtained from the milk of dairy cows fed with and without enriched olive cake (ECO and CTR, respectively) in order to evaluate nutritional, microbiological, volatile, and sensory differences in cheeses. ECO cheese showed greater (p < 0.05) MUFA and PUFA and polyphenols content and lower SFA content than CTR cheese. Microbiological analyses revealed the absence of Salmonella, Listeria monocytogenes, Escherichia coli, and E. coli O157, and no significant differences in the viable counts of the remaining microbial groups analyzed, between samples. Thermophilic lactococci were more prevalent in ECO cheese. The implementation of a culture-independent method, such as PCR-DGGE analyses, revealed the presence of a more diverse microbial population in both cheeses. Regarding the volatile compounds profile, long-chain free fatty acids were more abundant in the ECO cheese, resulting in a healthier free fatty acid profile. This study also showed that, especially for their appearance and taste, consumers mostly appreciated the ECO cheese. The results show that using enriched olive cake could enhance the sustainability and the quality of Ragusano cheese, improving not only the health of its consumers but also positively influencing tastes and acceptability.

A highly sensitive aptamer–antibody birecognized ECL sensing platform based on the cascaded reaction between CeO2@mrGO and Co-SAC@NC for E. coli O157:H7 in untreated milk

Rapid, sensitive and specific detection of foodborne pathogens is of great significance to the early warning and prevention of foodborne diseases and environmental pollution. Here, an electrochemiluminescent (ECL) biosensor with the cascaded reaction between two nanozymes was developed for the detection of E. coli O157:H7. Cobalt single-atom catalyst (Co-SAC@NC) with oxidase (OD) -like activity, as a co-reaction accelerator of O2, catalyzed oxygen to reactive oxygen species (ROSs) and boosted ECL of luminol-O2 system. Another nanozyme CeO2@mrGO with excellent phosphatase-like activity by the introduction of Fe was use to label Ab. CeO2@mrGO captured E. coli O157:H7, and then combined with Ap on the electrode surface through the affinity of aptamer and antibody to form a sandwich structure on the gold electrode (CeO2@mrGO-Ab/E. coli O157:H7/Ap-AuE). CeO2@mrGO converted AAP into AA, which consumed ROS and quenched ECL emission of luminol-O2 system. As a consequence, this ECL sensor had a linear response range of 17–1.7 × 105 CFU/mL with LOD of 2.78 CFU/mL. This aptamer-antibody birecognized system was able to be applied to assay E. coli O157:H7 in untreated contaminated milk samples with satisfactory results.

A HOF-101@AgNPs-based dual-signal mode aptasensor for electrochemiluminescence and fluorescence detection of E. coli O157:H7

Escherichia coli O157:H7 (E. coli O157:H7) emerges as a foodborne pathogen, emphasizing the imperative for creating precise detection tools. An ultrasensitive electrochemiluminescence/fluorescence (ECL/FL) dual-signal mode aptasensor was constructed for the detection of E. coli O157:H7. Ultrafine silver nanoparticles were loaded on the surface of hydrogen-bonded organic skeleton materials by in-situ photoreduction method, and then combined with aptamers that can identify specific targets to prepare HOF-101@AgNPs@Apt, greatly simplifying the ECL/FL dual-signal mode probe fabrication process and improving sensing reliability. HOF-101@AgNPs@Apt had both strong ECL luminescence and fluorescence, resulting in a high detection sensitivity. The low limit of detection (LOD) for ECL and FL were 0.48 CFU mL−1 and 2.39 CFU mL−1, respectively. Moreover, the proposed dual-signal mode aptasensor has been successfully applied to determine E. coli O157:H7 levels in tap water and milk with superior accuracy and high antiinterference capability, providing a promising method for food safety monitoring.

An Outbreak of Shiga Toxin-Positive Enteroaggregative Escherichia coli O104:H4 Related Hemolytic Uremic Syndrome in Turkey: A Multicenter Study

Introduction: Serious outbreaks of Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (STEC-HUS) have been reported globally. In 2011, Germany experienced a significant outbreak of HUS caused by enteroaggregative E. coli (EAEC) O104:H4 strain. Since then, no other outbreaks of this strain have been reported. This study aims to evaluate pediatric patients affected by the second documented worldwide outbreak of STEC-HUS (EAEC O104:H4 serotype) contaminating local drinking water. Methods: Medical records of patients hospitalized in five pediatric intensive care units (PICUs) diagnosed with STEC-HUS between July and September 2022 were evaluated retrospectively. Results: Eighteen patients (14 girls and 4 boys) were enrolled in the study. The median age was 7.4 (Interquartile range [IQR] 1.3–17) years. Abdominal pain was the most common symptom (100%). The mean duration between symptom onset and development of STEC-HUS was 3 days (IQ 1–9). EAEC O104:H4 serotype was detected in the stool samples of 8 patients. Neurological involvement was observed in 3 patients, cardiac involvement in 2 patients, and both in 1 patient. Two patients required respiratory support and dialysis was performed in 16 (88.8%) patients. Plasmapheresis was administered to 2 patients, and eculizumab was given to four. No mortality was reported during follow-up; the mean durations of PICU and hospital stays were 11.3 and 31.6 days, respectively. Conclusion: Outbreaks of HUS can have serious impacts on both mortality and morbidity. However, timely diagnosis and implementation of appropriate supportive care, including dialysis, respiratory support, and medical treatment for eligible patients, can lead to favorable outcomes.

Efficacy of an Edible Coating with Carvacrol and Citral in Frozen Strawberries and Blueberries to Control Foodborne Pathogens.

Adding essential oils in an edible coating could be an alternative for the food industry to control foodborne pathogens. In 2014, EFSA published a report highlighting the risk associated with Salmonella spp. and Norovirus in fresh and frozen berries. This study aimed to evaluate the efficacy of an edible coating (RP-7) with carvacrol and citral on reducing the population of Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes, and murine Norovirus (MNV-1) in frozen strawberries and blueberries. Before evaluating the efficacy, the best method for applying the coating on fruit was studied. The immersion method was selected, with an optimal drying time of 45 min. After this, the berries were frozen and stored for one, two, three, four, and eight weeks at -18 °C. In strawberries, all bacteria were reduced to below 0.7 log cfu/strawberry in the eighth week, and the MNV-1 infectivity showed a reduction of nearly 2 logarithmic units. In blueberries, S. enterica and E. coli O157:H7 were reduced to 0.8 log cfu/blueberries within a week, and MNV-1 achieved a reduction of 0.8 logarithmic units at the end of the assay. The application of RP-7 affected the studied microorganisms in frozen strawberries and blueberries.

Three birds with one stone: A nano zeolitic imidazolate framework-luciferase-antimicrobial peptide biocomposite-based biosensing platform for improving enzyme stability, detection sensitivity, and sterilization effect

Adenosine triphosphate-driven bioluminescence (ATP-BL) biosensors were widely employed for on-site screening of bacteria. However, unstable luciferase with strict storage conditions limited its field detection. Moreover, the traditional ATP-BL biosensors lacked the sterilization effect. In this study, a robust and multifunctional zeolitic imidazolate framework-90 decorated with luciferase and polyethylene glycol–antimicrobial peptides (ZIF-90@Luc-AMP) was prepared. It could not only enhance the activity and stability of luciferase at ambient temperatures (≥1 month) but also sensitively detect target bacteria via the bioluminescence (BL) method and kill them (three birds with one stone). During the detection process, the target pathogen Escherichia coli O157:H7 (E. coli O157:H7) was specifically captured on a phage-modified stir bar and formed a sandwich complex with ZIF-90@Luc-AMP. With the synergistic bacteriolysis of ZIF-90@Luc-AMP and the phage, the captured E. coli O157:H7 was decomposed and emitted adenosine triphosphate (ATP), achieving the sterilization effect. Meanwhile, the introduced luciferase catalyzed ATP to produce a BL signal, which was proportional to the concentration of E. coli O157:H7. Combining ZIF-90@Luc-AMP and a phage-labeled stir bar for target recognition and enrichment, the entire analytical process could be easily manipulated within 30 min with a low limit of detection (20 CFU/mL) through a portable ATP bioluminescent meter. The multifunctional ZIF-90@Luc-AMP biosensor with high stability, specificity, and sensitivity was also appropriate for rapid pathogen screening and antibacterial application in the wild.

Phage-modified dual-peak long-period fiber grating biosensor for ultrasensitive, rapid and specific detection of pathogen strains

Herein, we present an ultrasensitive, rapid and specific phage-modified dual-peak long-period fiber grating (Phage-DP-LPFG) biosensor for detecting foodborne pathogens. Compared to the single-peak resonance LPFG with a grating period of 360 μm, the DP-LPFG with a grating period of 163 μm offers enhanced sensitivity to refractive index changes caused by bacterial adsorption. By directionally immobilising phages on the DP-LPFG, the sensor achieves high specificity for target bacterial strains. Upon capturing the target strain, the short-wavelength near-infrared transmission loss peak undergoes a blue shift, whereas the long-wavelength transmission loss peak exhibits a red shift. The shift in spacing between the two peaks (Δλ) increases with higher bacterial capture, enabling the quantification of target strains based on Δλ changes. Using Escherichia coli O157:H7 (E. coli O157:H7) as a model, the Phage-DP-LPFG biosensor demonstrates a linear detection range of 25–108 CFU/mL with a low limit of detection of 8 CFU/mL in 10 min under optimal conditions. The biosensor was also tested on food samples such as fish and milk, showing no notable differences from standard methods but with reduced detection time. It was further extended to the detection of another foodborne pathogen strain Hafnia paralvei (MCCC 1K06097) (H. paralvei (MCCC 1K06097)) with satisfactory results. This study offers a novel approach for the rapid, sensitive and specific detection of trace pathogenic strains in foods.

Simultaneous detection of six major virulent genes of Escherichia coli O157:H7 from seafood by multiplex PCR and its validation through spiked study

Enterohaemorrhagic Escherichia coli (EHEC), mainly the serotype O157:H7 is a global concern in foodborne outbreaks,. The incidence of E. coli O157:H7 in seafood sold in India has been reported as 8.4%. The conventional method for the detection of E. coli O157:H7 from seafood is cumbersome and time consuming making this strain particularly challenging to detect. In this study a multiplex PCR was developed targeting six major virulence factors of the pathogen viz. shigatoxin 1 and 2, attachment and effacement factor, flagellar antigen, hemolysin gene and O157 antigen. The sensitivity of the multiplex PCR developed in the study was found to be 120 pg μl-1 of DNA and that of E. coli 0157:H7 spiked samples was 2 cfu ml-1. The multiplex PCR developed in this study showed 100% specificity in identifying E. coli O157:H7, effectively distinguishing it from non-target bacteria. This highly sensitive and specific multiplex PCR is the first of its kind to detect E. coli O157:H7 in seafood by targeting six major virulence genes. Keywords: E. coli O157:H7, EHEC, Foodborne pathogen, Seafood, Sensitivity, Shigatoxin, Specificity

Portable real-time determination of Escherichia coli O157:H7 and Staphylococcus aureus based on smartphones and hydrogels

The aptamers functionalized orange-emission carbon dots (OCDs) and green-emission carbon dots (GCDs) had dual-emission peaks with single excitation. Tungsten disulfide nanosheets (WS2 NSs)-triggered fluorescence quenching achieved the ratiometric fluorescence determination of Escherichia coli O157:H7 (E. coli O157:H7) and Staphylococcus aureus (S. aureus) with wide ranges of 18–1.8 × 106 and 37–3.7 × 107 CFU/mL and low detection limits of 8 and 20 CFU/mL, respectively. The results in real sample with recoveries of 90–101 % and RSD < 4.12 % were no significant difference from standard plate counting method. Meanwhile, the dual-color CDs were further adopted in the smartphone-assisted hydrogel platform and achieved speedy, sensitive, portable and real-time determination of E. coli O157:H7 and S. aureus in real samples. This work has not only developed ratiometric fluorescence detection and constructed a portable hydrogel platform, but also provided a unique strategy in developing a time-efficient and easy-to-use portable device in food safety monitoring.

Synergistic antimicrobial activities of aqueous extract derived from olive byproduct and their modes of action

BackgroundPlant-derived antimicrobials (PDAs) are considered a viable alternative to synthetic antimicrobial agents. Diverse antimicrobial mechanisms of PDAs significantly reduce the risk of developing antimicrobial resistance. Utilization of PDAs also offers economic and environmental advantages, as they can be derived from agricultural byproducts, such as olive pomace.ResultsIn this study, a green, water-based, ultrasound-assisted extraction (UAE) was deployed to obtain aqueous olive pomace extract (OPE) from dry olive pomace. Total phenolic content, extraction yield, chemical compositions, and antimicrobial activities of OPE were evaluated. In addition, the potential synergistic interaction between the phenolic components in OPE and the antimicrobial mechanisms underlying the synergistic interaction were characterized. The results show that ca. 25 mg GAE/g of extraction yields were achieved by the UAE of dry olive pomace. Based on the high-performance liquid chromatography (HPLC) analysis, diverse phenolic compounds such as gallic acid (GA), hydroxytyrosol (HT), and 4-hydroxyphenylacetic acid (4-HPA) were identified in OPE. OPE exhibited strong antimicrobial activities, and 0.2 mg GAE/mL of OPE achieved > 5 log reductions of Escherichia coli O157:H7 and Listeria innocua cells within 30 min of treatment. A 3D isobologram analysis demonstrated that OPE exhibited strong synergistic antimicrobial activities, compared to those of individual phenolic components (GA, HT, or 4-HPA), showing interaction index (γ) of 0.092 and 0.014 against E. coli O157:H7 and L. innocua, respectively (γ < 1: synergistic activity). Antimicrobial mechanism analyses revealed that phenolic components in OPE exerted strong synergistic activities through diverse modes of action, and increased levels of oxidative stress, membrane damage, and decreased levels of metabolic activities were observed in the OPE-treated bacterial cells.ConclusionsThese findings demonstrate an approach for valorizing agricultural byproducts to develop plant byproduct-based antimicrobials with strong synergistic activities. Multiple modes of action of this byproduct extract may enable the control of diverse microbes in food and agriculture systems.Graphical abstract

PH selective fluorometric detection of E. coli using water soluble polyphenothiazine

This work has investigated the use of a novel cationic conjugated polymer, Poly 10-(6-(3-methylimidazolidin-l-yl)hexyl)−9-Phenothiazine (PMP), as a sensing platform for a polymer-based fluorescence sensor for the detection of E. Coli O157:H7. Fourier Transform Infrared Spectroscopy (FTIR), ultraviolet radiation (UV), proton nuclear magnetic resonance (1HNMR), and photoluminescence (PL) analysis were used to characterise the synthesised polymer. The electrostatic interaction between single strand genomic DNA of E.coli (tDNA) and cationic polymer resulted in photoinduced charge transfer (PET) mediated quenching of the fluorescence intensity of PMP, which has been utilized as a tool for the detection DNA of E. coli (tDNA), since the decrease in photoluminescence intensity of cationic polymer was found to be proportional to the concentration of tDNA. The biosensor developed using PMP exhibits sensitive detection of tDNAin the range of 10−18 to 10−21 M concentration with a lowest detection limit of tDNA is 1 × 10−21 M.

Lipopolysaccharide Core Truncation in Invasive Escherichia coli O157:H7 ATCC 43895 Impairs Flagella and Curli Biosynthesis and Reduces Cell Invasion Ability.

Escherichia coli O157:H7 (E. coli O157) is known for causing severe foodborne illnesses such as hemorrhagic colitis and hemolytic uremic syndrome. Although E. coli O157 is typically regarded as an extracellular pathogen and a weak biofilm producer, some E. coli O157 strains, including a clinical strain ATCC 43895, exhibit a notable ability to invade bovine crypt cells and other epithelial cells, as well as to form robust biofilm. This invasive strain persists in the bovine host significantly longer than non-invasive strains. Various surface-associated factors, including lipopolysaccharides (LPS), flagella, and other adhesins, likely contribute to this enhanced invasiveness and biofilm formation. In this study, we constructed a series of LPS-core deletion mutations (waaI, waaG, waaF, and waaC) in E. coli O157 ATCC 43895, resulting in stepwise truncations of the LPS. This approach enabled us to investigate the effects on the biosynthesis of key surface factors, such as flagella and curli, and the ability of this invasive strain to invade host cells. We confirmed the LPS structure and found that all LPS-core mutants failed to form biofilms, highlighting the crucial role of core oligosaccharides in biofilm formation. Additionally, the LPS inner-core mutants ΔwaaF and ΔwaaC lost the ability to produce flagella and curli. Furthermore, these inner-core mutants exhibited a dramatic reduction in adherence to and invasion of epithelial cells (MAC-T), showing an approximately 100-fold decrease in cell invasion compared with the outer-core mutants (waaI and waaG) and the wild type. These findings underscore the critical role of LPS-core truncation in impairing flagella and curli biosynthesis, thereby reducing the invasion capability of E. coli O157 ATCC 43895.

Establishment of LAMP-CRISPR/Cas12a for rapid detection of Escherichia coli O157:H7 and one-pot detection

Escherichia coli O157:H7 is a pathogenic serotype of Escherichia coli. Consumption of food contaminated with E. coli O157:H7 could cause a range of diseases. Therefore, it is of great importance to establish rapid and accurate detection methods for E. coli O157:H7 in food. In this study, based on LAMP and combined with the CRISPR/cas12a system, a sensitive and specific rapid detection method for E. coli O157:H7 was established, and One-Pot detection method was also constructed. The sensitivity of this method could stably reach 9.2 × 10° CFU/mL in pure culture, and the whole reaction can be completed within 1 h. In milk, E. coli O157:H7 with an initial contamination of 7.4 × 10° CFU/mL only needed to be cultured for 3 h to be detected. The test results can be judged by the fluorescence curve or by visual observation under a UV lamp, eliminating instrument limitations and One-Pot detection can effectively prevent the problem of false positives. In a word, the LAMP-CRISPR/cas12a system is a highly sensitive and convenient method for detecting E. coli O157:H7.