A ratiometric SERS aptasensor based on catalytic hairpin self-assembly mediated cyclic signal amplification strategy for the reliable determination of E. coli O157:H7.

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly (CHA) mediated cyclic signal amplification strategy was developed for the rapid and reliable determination of Escherichia coli O157:H7. The recognition probe was synthesized by modifying magnetic beads with blocked aptamers, and the SERS probe was constructed by functionalizing gold nanoparticles (Au NPs) with hairpin structured DNA and 4-mercaptobenzonitrile (4-MBN). The recognition probe captured E. coli O157:H7 specifically and released the blocker DNA, which activated the CHA reaction on the SERS probe and turned on the SERS signal of 6-carboxyl-x-rhodamine (ROX). Meanwhile, 4-MBN was used as an internal reference to calibrate the matrix interference. Thus, sensitive and reliable determination and quantification of E. coli O157:H7 was established using the ratio of the SERS signal intensities of ROX to 4-MBN. This aptasensor enabled detection of 2.44 × 102 CFU/mL of E. coli O157:H7 in approximately 3 h without pre-culture and DNA extraction. In addition, good reliability and excellent reproducibility were observed for the determination of E. coli O157:H7 in spiked water and milk samples. This study offered a new solution for the design of rapid, sensitive, and reliable SERS aptasensors.

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.

Hybrid nanoflower-based electrochemical lateral flow immunoassay for Escherichia coli O157 detection.

An electrochemical biosensor has been developed for detection of Escherichia coli O157 by integrating lateral flow with screen-printed electrodes. The screen-printed electrodes were attached under the lateral flow detection line, and organic-inorganic nanoflowers prepared from E. coli O157-specific antibodies as an organic component were attached to the lateral flow detection line. In the presence of E. coli O157, an organic-inorganic nanoflower-E. coli O157-antimicrobial peptide-labelled ferrocene sandwich structure is formed on the lateral flow detection line. Differential pulse voltammetry is applied using a smartphone-based device to monitor ferrocene on the detection line. The resulting electrochemical biosensor could specifically detect E. coli O157 with a limit of detection of 25 colony-forming units mL-1. Through substitution of antibodies of organic components in organic-inorganic nanoflowers, biosensors have great potential for the detection of other pathogens in biomedical research and clinical diagnosis.

Vibrio cholerae O1 and Escherichia coli O157:H7 from drinking water and wastewater in Addis Ababa, Ethiopia.

BACKGROUND: In Addis Ababa, Ethiopia, open ditches along innner roads in residential areas serve to convey domestic wastewater and rainwater away from residences. Contamination of drinking water by wastewater through faulty distribution lines could expose households to waterborne illnesses. This prompted the study to assess the microbiological safety of wastewater and drinking water in Addis Ababa, identify the pathogens therein, and determine their antibiotic resistance patterns. RESULTS VIBRIO CHOLERAE: O1, mainly Hikojima serotype, was isolated from 23 wastewater and 16 drinking water samples. Similarly, 19 wastewater and 10 drinking water samples yielded Escherichia coli O157:H7. V. cholerae O1 were 100% resistant to the penicillins (Amoxacillin and Ampicillin), and 51-82% were resistant to the cephalosporins. About 44% of the V. cholerae O1 isolates in this study were Extended Spectrum Beta-Lactamase (ESBL) producers. Moreover, 26% were resistant to Meropenem. Peperacillin/Tazobactam was the only effective ß-lactam antibiotic against V. cholerae O1. V. cholerae O1 isolates showed 37 different patterns of multiple resistance ranging from a minimum of three to a maximum of ten antimicrobials. Of the E. coli O157:H7 isolates, 71% were ESBL producers. About 96% were resistant to Ampicillin. Amikacin and Gentamicin were very effective against E. coli O157:H7 isolates. The isolates from wastewater and drinking water showed multiple antibiotic resistance against three to eight antibiotic drugs. CONCLUSIONS: Open ditches for wastewater conveyance along innner roads in residence areas and underground faulty municipal water distribution lines could be possible sources for V. cholerae O1 and E. coli O157:H7 infections to surrounding households and for dissemination of multiple drug resistance in humans and, potentially, the environment.

Electroanalytical Platform for Rapid E. coli O157:H7 Detection in Water Samples.

There is a pressing need to enhance early detection methods of E. coli O157:H7 to mitigate the occurrence and consequences of pathogenic contamination and associated outbreaks. This study highlights the efficacy of a portable electrochemical sensing platform that operates without faradaic processes towards detecting and quantifying E. coli O157:H7. It is specifically tailored for quick identification in potable water. The assay processing time is approximately 5 min, addressing the need for swift and efficient pathogen detection. The sensing platform was constructed utilizing specific, monoclonal E. coli antibodies, based on single-capture, non-faradaic, electrochemical immunoassay principles. The E. coli sensor assay underwent testing over a wide concentration range, spanning from 10 to 105 CFU/mL, and a limit of detection (LoD) of 1 CFU/mL was demonstrated. Significantly, the sensor's performance remained consistent across studies, with both inter- and intra-study coefficients of variation consistently below 20%. To evaluate real-world feasibility, a comparative examination was performed between laboratory-based benchtop data and data obtained from the portable device. The proposed sensing platform exhibited remarkable sensitivity and selectivity, enabling the detection of minimal E. coli concentrations in potable water. This successful advancement positions it as a promising solution for prompt on-site detection, characterized by its portability and user-friendly operation. This study presents electrochemical-based sensors as significant contributors to ensuring food safety and public health. They play a crucial role in preventing the occurrence of epidemics and enhancing the supervision of water quality.

Au-Pt Coating Improved Catalytic Stability of Au@AuPt Nanoparticles for Pressure-Based Point-of-Care Detection of Escherichia coli O157:H7.

Point-of-care testing (POCT) technologies facilitate onsite detection of pathogens in minutes to hours. Among various POCT approaches, pressure-based sensors that utilize gas-generating reactions, particularly those catalyzed by nanozymes (e.g., platinum nanoparticles, PtNPs, or platinum-coated gold nanoparticles, and Au@PtNPs) have been shown to provide rapid and sensitive detection capabilities. The current study introduces Au-Pt alloy-coated gold nanoparticles (Au@AuPtNPs), an innovative nanozyme with enhanced catalytic activity and relatively high stability. For pathogen detection, Au@AuPtNPs are modified with H1 or H2 hairpin DNAs that can be triggered to undergo a hybridization chain reaction (HCR) that leads to their aggregation upon recognition by an initiator strand (Ini) with H1-/H2-complementary aptamers tethered to magnetic beads (MBs). Pathogen binding to the aptamer exposes Ini, which then binds Au@AuPtNPs and initiates a HCR, resulting in Au@AuPtNP aggregation on MBs. These Au@AuPtNP aggregates exhibit strong catalysis of O2 from the H2O2 substrate, which is measured by a pressure meter, enabling detection of Escherichia coli (E. coli) O157:H7 at concentrations as low as 3 CFU/mL with high specificity. Additionally, E. coli O157:H7 could also be detected in simulated water and tea samples. This method eliminates the need for costly, labor- and training-intensive instruments, supporting its further testing and validation for deployment as a rapid-response POCT application in the detection of bacterial contaminants.

Rapid and Sensitive Quantification of Bacterial Viability Using Ratiometric Fluorescence Sensing.

Bacterial viability assessment plays an important role in food-borne pathogen detection and antimicrobial drug development. Here, we first used GelRed as a DNA-binding stain for a bacterial viability assessment. It was found that live bacteria were able to exclude GelRed, which however could easily penetrate dead ones and be absorbed nonspecifically on the bacterial periplasm. Cations were used to reduce the nonspecific adsorption and greatly increase the red fluorescence ratio of dead to live bacteria. Combined with SYTO 9 (a membrane-permeable dye) for double-staining, a ratiometric fluorescent method was established. Using Escherichia coli O157:H7 as a bacteria model, the ratiometric fluorescent method can probe dead bacteria as low as 0.1%. A linear correlation between the ratiometric fluorescence and the theoretical ratio of dead bacteria was acquired, with a correlation coefficient R2 of 0.97. Advantages in sensitivity, accuracy, and safety of the GelRed/SYTO9-based ratiometric fluorescent method against traditional methods were demonstrated. The established method was successfully applied to the assessment of germicidal efficacy of different heat treatments. It was found that even 50 °C treatment could lead to the death of minor bacteria. The as-developed method has many potential applications in microbial researches, and we believe it could be expanded to the viability assessment of mammalian cells.

On-Chip Capture, Raman-Silent Polymer Labeling, and Digital Mapping Analysis of Escherichia coli O157:H7 in Beverages All-in-One.

Escherichia coli O157:H7 is one of the most susceptible foodborne pathogens, easily causing food poisoning and other health risks. It is of great significance to establish a quantitative method with higher sensitivity and less time consumption for foodborne pathogens analysis. The Raman-silent signal has a good performance for avoiding interference from the food matrix so as to achieve accurate signal differentiation. In this work, we presented a preparation-mapping all-in-one method for digital mapping analysis. We prepared a functionalized Raman-silent polymer label of Escherichia coli O157:H7, which was captured on a porous 4-mercaptophenylboric acid@Ag foam chip. To improve accuracy and widen the detection range, a digital mapping quantitative strategy was employed in data extraction and processing. By transfer mapping information into digitized statistical results, the limitation of obtaining reproducible intensity values just by randomly selected spots on the substrate can be addressed. With a wide linear range of 1.0 × 101-1.0 × 105 CFU mL-1 and a limit of detection of 4.4 CFU mL-1, this all-in-one method had good sensitivity performance. Also, this method achieved good precision and selectivity in a series of experiments and was successfully applied to the analysis of beverage samples.

Simultaneous SERS-decoding detection of multiple pathogens in drinking water with home-made portable double-layer filtration and concentration device.

The engineering of a home-made portable double-layer filtration and concentration device with the common syringe for rapid analysis of water samples is reported. The core elements of the device were two installed filtration membranes with different pore sizes for respective functions. The upper filtration membrane was used for preliminary intercepting large interfering impurities (interception membrane), while the lower filtration membrane was used for collecting multiple target pathogens (enrichment membrane) for determination. This combination can make the contaminated environmental water, exemplified by surface water, filtrated quickly through the device and just retained the target bacteria of Escherichia coli O157:H7, Staphylococcus aureus, and Listeria monocytogenes on the lower enrichment membrane. Integrating with surface-enhanced Raman spectra (SERS) platform to decode the SERS-Tags (SERS-TagCVa, SERS-TagR6G, and SERS-TagMB) already labeled on each of the enriched bacteria based the antibody-mediated immuno-recognition effect, fast separation, concentration, and detection of multiple pathogenic bacteria from the bulk of contaminated environmental water were realized. Results show that within 30 min, all target bacteria in the lake water can be simultaneously and accurately measured in the range from 101 to 106 CFU mL-1 with detection limit of 10.0 CFU mL-1 without any pre-culture procedures. This work highlights the simplicity, rapidness, cheapness, selectivity, and the robustness of the constructed method for simultaneous detecting multiple pathogens in aqueous samples. This protocol opens a new avenue for facilitating the development of versatile analytical tools for drinking water and food safety monitoring in underdeveloped or developing countries.

Fluorescent biosensor based on magnetic separation platform and spore-like breakable organosilica nanocapsules controlled-release carbon dots for the detection of Escherichia coli O157:H7.

Ultrasensitive and rapid detection of low concentration of Escherichia coli O157: H7 (E. coli O157:H7) in food is essential for food safety and public health. In this study, A novel fluorescence signal amplification biosensor based on magnetic separation platform and red fluorescent carbon dots (R-CDs)-encapsulated breakable organosilica nanocapsules (BONs) for ultrasensitive detection of E. coli O157:H7 was established. Wulff-type boronic acid functionalized magnetic nanoparticles (MNPs@B-N/APBA) with broad-spectrum bacterial recognition ability were synthesized for the first time to recognize and capture E. coli O157: H7 in food samples. R-CDs@BONs labeled with anti-E. coli O157:H7 monoclonal antibody (mAb@R-CDs@BONs-NH2) were used as the second recognition element to ensure the specificity for E. coli O157:H7 and form MNPs@B-N/APBA∼ E. coli O157:H7∼mAb@R-CDs@BONs-NH2 sandwich complexes, followed by releasing R-CDs to generate amplified fluorescence response signals for quantitative detection of E. coli O157:H7. The proposed method had a limit of detection with 25 CFU/mL in pure culture and contaminated lettuce samples, which the whole detection process took about 120 min. This fluorescence signal amplification biosensor has the potential to detect other pathogens in food by altering specific antibodies.

ENTEROHEMORRHAGIC ESCHERICHIA COLI LEADING TO HAEMOLYTIC UREMIC SYNDROME - CASE STUDY AND REVIEW.

Escherichia coli is a gram-negative bacillus and considered to be the normal pathogen of intestinal and extraintestinal manifestations depending upon the strain. A variety of strains exist that are responsible for causing myriads of clinical presentation. E.coli O157: H7 being the most common and severe bacterial pathogen is the leading cause of bloody diarrhea. EHEC (Enterohemorrhagic E.coli) is responsible for causing severe complications like HC (Hemorrhagic colitis). Herein, we present the case of a young girl with E.coli O157:H7 infection and review the related literature. A previously healthy 37-year-old female presented with bloody diarrhea, fever, headache, and lower abdominal pain. As per history she had eaten a hamburger, denied any recent travel and absence of inflammatory bowel disease or bloody stools in family history. Physical examination revealed normal vital signs and the physical findings were unremarkable except for severe abdominal pain. Her stool was hem-occult positive. The complete blood count was within normal limits except neutrophilia and leukocytosis. An abdominal ultrasound showed thickened bowel loops consistent with colitis. First week of her hospital course, she continued to have bloody diarrhea and severe abdominal pain. Her final stool submitted to the laboratory on day 7 was consistent with a blood clot, following her developed low urine output and hematuria, with a serum creatinine of 2.1 mg/dl on day 5. Her renal symptoms were treated with fluids. She was given supportive treatment, and her platelet count and hemoglobin were stabilized. In early stages of bloody diarrhea, parental hydration plays a major role in accelerating volume expansion. Rapid stool analysis for these bacteria can alert specialists to deal with severe complications like HUS.

Detection of the chuA gene encoding the invasive enterohemorrhagic species Escherichia coli 0157:H7 using qPCR in horse feces samples on Sumbawa Island, Indonesia.

Background: Bacterial identification can be done using various testing techniques. Molecular techniques are often used to research dangerous diseases, an approach using genetic information on the pathogenic agent. The enterohemorrhagic invasive species Escherichia coli 0157:H7 was identified from the feces of working horses on the island of Sumbawa. Another advance in molecular technology is genome amplification with qPCR which is the gold standard for detecting E. coli. Aim: This study aims to detect and identify the invasive species E. coli 0157:H7 using the gene encoding chuA with the qPCR method sourced from horse feces. Methods: Fresh fecal samples from horses on Sumbawa Island were isolated and identified, then continued with molecular examination using the gene encoding chuA using the qPCR method. Results: qPCR testing in this study showed that six sample isolates that were positive for E. coli 0157:H7 were detected for the presence of the chuA gene, which is a gene coding for an invasive species of E. coli bacteria. The highest to lowest Cq values and Tm from the qPCR results of the sample isolates were 15.98 (4KJ), 14.90 (19KG), 14.6 (3KJ), 13.77 (20KG), 12.56 (5KGB), and 12.20 (6KJ). Tm values are 86.7 (4KJ), 86.69 (3KJ), 86.56 (5KGB), 85.88 (20KGB), 85.81 (19KG), and 85.74 (6KJ). Conclusion: Validation, standardization of the development, and modification of qPCR technology must be carried out to harmonize testing throughout to avoid wrong interpretation of the test results so that the determination of actions to eradicate and control diseases originating from animals in the field does not occur.

Shiga Toxin-Producing Escherichia coli O157:H7 Illness Outbreak Associated with Untreated, Pressurized, Municipal Irrigation Water - Utah, 2023.

During July-September 2023, an outbreak of Shiga toxin-producing Escherichia coli O157:H7 illness among children in city A, Utah, caused 13 confirmed illnesses; seven patients were hospitalized, including two with hemolytic uremic syndrome. Local, state, and federal public health partners investigating the outbreak linked the illnesses to untreated, pressurized, municipal irrigation water (UPMIW) exposure in city A; 12 of 13 ill children reported playing in or drinking UPMIW. Clinical isolates were genetically highly related to one another and to environmental isolates from multiple locations within city A's UPMIW system. Microbial source tracking, a method to indicate possible contamination sources, identified birds and ruminants as potential sources of fecal contamination of UPMIW. Public health and city A officials issued multiple press releases regarding the outbreak reminding residents that UPMIW is not intended for drinking or recreation. Public education and UPMIW management and operations interventions, including assessing and mitigating potential contamination sources, covering UPMIW sources and reservoirs, indicating UPMIW lines and spigots with a designated color, and providing conspicuous signage to communicate risk and intended use might help prevent future UPMIW-associated illnesses.

Synthetic phage-based approach for sensitive and specific detection of Escherichia coli O157.

Escherichia coli O157 can cause foodborne outbreaks, with infection leading to severe disease such as hemolytic-uremic syndrome. Although phage-based detection methods for E. coli O157 are being explored, research on their specificity with clinical isolates is lacking. Here, we describe an in vitro assembly-based synthesis of vB_Eco4M-7, an O157 antigen-specific phage with a 68-kb genome, and its use as a proof of concept for E. coli O157 detection. Linking the detection tag to the C-terminus of the tail fiber protein, gp27 produces the greatest detection sensitivity of the 20 insertions sites tested. The constructed phage detects all 53 diverse clinical isolates of E. coli O157, clearly distinguishing them from 35 clinical isolates of non-O157 Shiga toxin-producing E. coli. Our efficient phage synthesis methods can be applied to other pathogenic bacteria for a variety of applications, including phage-based detection and phage therapy.

Occurrence, molecular characterization, and antimicrobial susceptibility of sorbitol non-fermenting Escherichia coli in lake water, fish and humans in central Oromia, Ethiopia.

Contaminated lake water and fish can be sources of bacterial pathogens of public health concern, including pathogenic E. coli. Within Ethiopia, specifically, Central Oromia, raw fish consumption is a common practice. Although there are few reports on occurrence of E. coli O157 in fish destined for human consumption and children under five years, information on the transmission pathways of E. coli O157 and other sorbitol non-fermenting (SN-F) E. coli from water-to-fish-to-human, and their virulence factors and antimicrobial resistant determinants along the fish supply chain is lacking. The study aimed to investigate the occurrence, molecular characteristics, and antimicrobial susceptibility of E. coli O157 and other SN-F E. coli strains in fish, lake water and humans in central Oromia, Ethiopia. A total of 750 samples (450 fish samples, 150 water samples, 150 human stool samples) were collected from five lakes and three health facilities. The samples were processed following the standard protocol recommended by European Food Safety Authority and Kirby-Bauer disc diffusion method for detection of the bacteria, and antimicrobial susceptibility tests, respectively. Molecular characterization of presumptive isolates was performed using Whole-Genome Sequencing (WGS) for serotyping, determination of virulence factors, antimicrobial resistance traits, and genetic linkage of the isolates. Overall, 3.9% (29/750) of the samples had SN-F E. coli; of which 6.7% (n = 10), 1.8% (n = 8) and 7.3% (n = 11) were retrieved from water, fish, and diarrheic human patients, respectively. The WGS confirmed that all the isolates were SN-F non-O157: H7 E. coli strains. We reported two new E. coli strains with unknown O-antigen from fish and human samples. All the strains have multiple virulence factors and one or more genes encoding for them. Genetic relatedness was observed among strains from the same sources (water, fish, and humans). Most isolates were resistant to ampicillin (100%), tetracycline (100%), cefotaxime (100%), ceftazidime (100%), meropenem (100%), nalidixic acid (93.1%) and sulfamethoxazole/trimethoprim (79.3%). Majority of the strains were resistant to chloramphenicol (58.6%) and ciprofloxacin (48.3%), while small fraction showed resistance to azithromycin (3.45%). Isolates had an overall MDR profile of 87.5%. Majority, (62.1%; n = 18) of the strains had acquired MDR traits. Genes encoding for mutational resistance and Extended-spectrum beta-lactamases (ESBL) were also detected. In conclusion, our study revealed the occurrence of virulent and MDR SN-F E. coli strains in water, fish, and humans. Although no genetic relatedness was observed among strains from various sources, the genomic clustering among strains from the same sources strongly suggests the potential risk of transmission along the supply chain at the human-fish-environment interface if strict hygienic fish production is not in place. Further robust genetic study of the new strains with unknown O-antigens, and the epidemiology of SN-F E. coli is required to elucidate the molecular profile and public health implications of the pathogens.

ICP-MS based detection method combined with Au NP and Ag NP labeling for bacteremia diagnosis.

Bacteremia, as a serious infectious disease, has an increasing incidence and a high mortality rate. Early diagnosis and early treatment are crucial for improving the cure rate. In this work, we proposed an inductively coupled plasma mass spectrometry (ICP-MS)-based detection method combined with gold nanoparticle (Au NP) and silver nanoparticle (Ag NP) labeling for the simultaneous detection of Salmonella and Escherichia coli (E. coli O157:H7) in human blood samples. Salmonella and E. coli O157:H7 were captured by magnetic beads coupled with anti-8G3 and anti-7C2, and then specifically labeled by Au NP-anti-5H12 and Ag NP-anti-8B1 respectively, which were used as signal probes for ICP-MS detection. Under the optimal experimental conditions, the limits of detection of 164 CFU mL-1 for Salmonella, 220 CFU mL-1for E. coli O157:H7 and the linear ranges of 400-80,000 CFU mL-1Salmonella, 400-60,000 CFU mL-1 E. coli O157:H7 were obtained. The proposed method can realize the simultaneous detection of two types of pathogenic bacteria in human whole blood in 3.5 h, showing great potential for the rapid diagnosis of bacteremia in clinic.

A Dual-mode platform for the rapid detection of Escherichia coli O157:H7 based on CRISPR/Cas12a and RPA.

Escherichia coli O157:H7 (E. coli O157:H7) is a foodborne pathogenic microorganism that is commonly found in the environment and poses a significant threat to human health, public safety, and economic stability worldwide. Thus, early detection is essential for E. coli O157:H7 control. In recent years, a series of E. coli O157:H7 detection methods have been developed, but the sensitivity and portability of the methods still need improvement. Therefore, in this study, a rapid and efficient testing platform based on the CRISPR/Cas12a cleavage reaction was constructed. Through the integration of recombinant polymerase amplification and lateral flow chromatography, we established a dual-interpretation-mode detection platform based on CRISPR/Cas12a-derived fluorescence and lateral flow chromatography for the detection of E. coli O157:H7. For the fluorescence detection method, the limits of detection (LODs) of genomic DNA and E. coli O157:H7 were 1.8 fg/µL and 2.4 CFU/mL, respectively, within 40 min. Conversely, for the lateral flow detection method, LODs of 1.8 fg/µL and 2.4 × 102 CFU/mL were achieved for genomic DNA and E. coli O157:H7, respectively, within 45 min. This detection strategy offered higher sensitivity and lower equipment requirements than industry standards. In conclusion, the established platform showed excellent specificity and strong universality. Modifying the target gene and its primers can broaden the platform's applicability to detect various other foodborne pathogens.

ß-Galactosidase-triggered in situ synthesis of yellow emitting silicon nanoparticle and its application in visual detection of E. coli O157:H7 and drug susceptibility test.

The sensitive detection of foodborne pathogenic and rapid antibiotic susceptibility testing (AST) is of great significance. This paper reports the enzyme-triggered in situ synthesis of yellow emitting silicon nanoparticles (SiNPs) and the detection of Escherichia coli (E. coli) O157:H7 in food samples and the rapid AST. The rapid counting of E. coli O157:H7 has been achieved through direct visual observation, equipment detection, and smartphone digitalization. A simple detection platform based on smartphone senses and cotton swabs has been established. Meanwhile, rapid AST based on enzyme-catalyzed SiNPs can intuitively obtain colorimetric samples. This paper established a system for bacterial enzyme-triggered in situ synthesis of SiNPs, with high responsiveness, luminescence ratio, and specificity. The detection limit for E. coli O157:H7 can reach 100 CFU/mL during 5 h, and the recovery efficiency ranges from 90.14% to 110.16%, which makes it a promising strategy for the rapid detection of E. coli O157:H7 and AST.

Green-Synthesized Amino Carbons for Impedimetric Biosensing of E. coli O157:H7.

This study describes the synthesis of amino-functionalized carbon nanoparticles derived from biopolymer chitosan using green synthesis and its application toward ultrasensitive electrochemical immunosensor of highly virulent Escherichia coli O157:H7 (E. coli O157:H7). The inherent advantage of high surface-to-volume ratio and enhanced rate transfer kinetics of nanoparticles is leveraged to push the limit of detection (LOD), without compromising on the selectivity. The prepared carbon nanoparticles were systematically characterized by employing CO2-thermal programmed desorption (CO2-TPD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-visible), and transmission electron microscopy (TEM). The estimated limit of detection of 0.74 CFU/mL and a sensitivity of 5.7 ((ΔRct/Rct)/(CFU/mL))/cm2 in the electrochemical impedance spectroscopy (EIS) affirm the utility of the sensor. The proposed biosensor displayed remarkable selectivity against interfering species, making it well suited for real-time applications. Moreover, the chitosan-derived semiconducting amino-functionalized carbon shows excellent sensitivity in a comparative analysis compared to highly conducting amine-functionalized carbon synthesized via chemical modification, demonstrating its vast potential as an E. coli sensor.

Detection of Escherichia coli O157H7 and Campylobacter jejuni in Bovine Carcasses in Two Slaughterhouses in Bio-Bío District, Chile.

Escherichia coli O157:H7 (E. coli O157:H7) and Campylobacter jejuni (C. jejuni) are pathogenic microorganisms that can cause severe clinical symptoms in humans and are associated with bovine meat consumption. Specific monitoring for E. coli O157: H7 or C. jejuni in meat is not mandatory under Chilean regulations. In this study, we analyzed 544 samples for the detection of both microorganisms, obtained from 272 bovine carcasses (280 kg average) at two slaughterhouses in the Bio-Bío District, Chile. Sampling was carried out at post-shower of carcasses and after channel passage through the cold chamber. Eleven samples were found to be positive for E. coli O157:H7 (4.0%) using microbiological and biochemical detection techniques and were subjected to a multiplex PCR to detect fliC and rfbE genes. Six samples (2.2%) were also found to be positive for the pathogenicity genes stx1, stx2, and eaeA. Twenty-two carcasses (8.0%) were found to be positive for C. jejuni using microbiological and biochemical detection techniques, but no sample with amplified mapA gene was found.