Rapid detection of Clostridium perfringens in food by loop-mediated isothermal amplification combined with a lateral flow biosensor

Prevalence of epsilon toxin-producing Clostridium perfringens isolates among patients with multiple sclerosis and neuromyelitis optica spectrum disorder in Iran

BACKGROUND

Clostridium perfringens epsilon toxin (ETX) is a potent neurotoxin that crosses the blood-brain barrier (BBB), and has been suggested to be involved in demyelinating CNS disorders. Here, we investigated the prevalence of C. perfringens and anti-ETX immunoglobulin G (IgG) and immunoglobulin M (IgM) antibody levels in stool and sera of patients with multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) compared to healthy controls.

METHODS

Between September 2019 and June 2020, 43 stool and 43 sera specimens were collected from MS (n = 33) and NMOSD (n = 10) patients, and 49 samples from healthy subjects. Stool samples were cultured for the presence of C. perfringens and PCR was used to detect etx-encoding gene. The level of serum IgG and IgM against ETX was examined using competitive ELISA. The predictive value of sex, age, ETX IgG and IgM levels, and C. perfringens was assessed using multivariable prediction models, with all models trained on the full set of variables. Independent contributions were evaluated separately using logistic regression (LR) analysis.

RESULTS

Totally, 11 C. perfringens were isolated from MS (n = 4), NMOSD (n = 2), and healthy (n = 5) subjects. The etx gene was detected in 1/4 (25%) isolates from MS and 2/2 (100%) from NMOSD patients, while none of the isolates from healthy subjects carried the gene. The analysis of serum IgG and IgM level against ETX showed no significant difference between patients and healthy subjects. Among the prediction models used, LR and Naïve Bayes (NB), trained on all predictor variables, exhibited the highest statistical accuracy for MS diagnosis, with AUC = 0.71 and AUC = 0.93, respectively. Among individual parameters, sex (AUC = 0.63) and IgG level (AUC = 0.57) were the most reliable predictors. The nomogram prediction demonstrated that the probability of patients' risk of developing MS and NMOSD can be predicted using these predictors.

CONCLUSIONS

Our findings indicate a potential association between ETX-producing C. perfringens strains and MS/NMOSD diseases, as its presence was detected in a subset of patient samples. However, no significant differences in anti-ETX antibody levels were observed between control and patients. Our prediction models highlighted key demographic and serological factors that may contribute to MS diagnosis. These results highlight the need for further research to meticulously decipher the biological interplay of C. perfringens and its ETX toxin with the development of MS and NMOSD.

Three-mode ratiometric biosensor based on integrated DNA-driven magnetic beads for Clostridium perfringens detection

A three-mode biosensor incorporated ratiometric (electrochemical/colorimetric, electrochemical/photothermal) into its design was constructed using DNA-driven magnetic beads (DMBs) as a bridge to detect C. perfringens. It further enhances the accuracy of detection results while maintaining compatibility with applications in multiple scenarios. Briefly, the G-quadruplex was combined with aptamer and immobilized onto magnetic beads through amide-bond, resulting in the integration of DMBs. The DMBs and supernatant were separated by magnetic separation when the target was present. Subsequently, the DMBs were utilized to construct the electrochemical biosensor, whereas the supernatant was used to construct colorimetric and photothermal biosensors. The limits of detection the ratiometric biosensor were ultimately reduced to 0.26 and 0.27 lg CFU g-1, respectively, in comparison to the single three-mode biosensor. Moreover, this biosensor had been applied in real-sample assays successfully. The establishment of this platform provides a new method for detecting pathogens in the fields of food safety and environmental monitoring.

A drop dispenser for simplifying on-farm detection of foodborne pathogens

Nucleic-acid biosensors have emerged as useful tools for on-farm detection of foodborne pathogens on fresh produce. Such tools are specifically designed to be user-friendly so that a producer can operate them with minimal training and in a few simple steps. However, one challenge in the deployment of these biosensors is delivering precise sample volumes to the biosensor's reaction sites. To address this challenge, we developed an innovative drop dispenser using advanced 3D printing technology, combined with a hydrophilic surface chemistry treatment. This dispenser enables the generation of precise sample drops, containing DNA or bacterial samples, in volumes as small as a few micro-liters (∼20 to ∼33 μL). The drop generator was tested over an extended period to assess its durability and usability over time. The results indicated that the drop dispensers have a shelf life of approximately one month. In addition, the device was rigorously validated for nucleic acid testing, specifically by using loop-mediated isothermal amplification (LAMP) for the detection of Escherichia coli O157, a prevalent foodborne pathogen. To simulate real-world conditions, we tested the drop dispensers by integrating them into an on-farm sample collection system, ensuring they deliver samples accurately and consistently for nucleic acid testing in the field. Our results demonstrated similar performance to commercial pipettors in LAMP assays, with a limit of detection of 7.8×106 cells/mL for whole-cell detection. This combination of precision, ease of use, and durability make our drop dispenser a promising tool for enhancing the effectiveness of nucleic acid biosensors in the field.

Establishment and application of a rapid visual detection method for Clostridium perfringens in chicken products based on helical loop-mediated isothermal amplification (HAMP)

Clostridium perfringens is a significant foodborne pathogen in chicken products. Rapid on-site detection of C. perfringens is crucial for mitigating the incidence of foodborne illnesses by enabling the prompt identification and recall of contaminated food products. A rapid and visual detection method for C. perfringens in chicken products was developed using helical loop-mediated isothermal amplification (HAMP) technology combined with SYBR Green I fluorescent staining. The reaction temperature, time, and reagent concentrations of HAMP technique were optimized firstly. HAMP displayed high specificity, effectively distinguishing C. perfringens from 18 other common pathogens in chicken products. HAMP also exhibited higher sensitivity (78 fg/µL) compared to endpoint PCR and real-time quantitative PCR (qPCR). The detection limit of HAMP for non-enriched samples was 6.8 × 102 CFU/g, which improved to 68 and 6.8 CFU/g after 5 and 10 h of enrichment, respectively. The detection limit of HAMP was lower by 2 and 1 orders of magnitude compared to endpoint PCR and qPCR under the same conditions. On-site testing of commercially available ready-to-eat chicken products showed that HAMP had the same results as traditional culture methods, indicating the significant potential of HAMP for on-site detection of C. perfringens. This method offered a rapid, accurate, and visual means of detecting C. perfringens in chicken products, making it well-suited for on-site testing. This research represented the first use of the HAMP method for detecting C. perfringens.

Revolutionizing food safety with electrochemical biosensors for rapid and portable pathogen detection

Foodborne diseases remain a worldwide concern, despite the advances made in sanitation, pathogen surveillance and food safety management systems. The methods routinely applied for detecting pathogens in foods are time consuming, labor intensive and usually require trained and qualified individuals. The objective of this review was to highlight the use of biosensors, with a focus on the electrochemical devices, as promising alternatives for detecting foodborne pathogens. These biosensors present high speed for obtaining results, with the possibility of evaluating foods in real time, at low cost, ease of use, in addition to being compact and portable. These aspects are considered advantageous and suitable for use in food safety management systems. This work also shows some limitations for the application of biosensors, and we present perspectives with the development and use of nanomaterials.

Recombinase polymerase amplification combined with lateral flow biosensor for rapid visual detection of Clostridium perfringens in chicken meat and milk

Aims

Clostridium perfringens is one of the major anaerobic pathogen causing food poisoning and animal enteritis. With the rise of antibiotic resistance and the restrictions of the use of antibiotic growth promoting agents (AGPs) in farming, Clostridium enteritis and food contamination have become more common. It is time-consuming and labor-intensive to confirm the detection by standard culture methods, and it is necessary to develop on-site rapid detection tools. In this study, a combination of recombinase polymerase amplification (RPA) and lateral flow biosensor (LFB) was used to visually detect C. perfringens in chicken meat and milk.

Methods and results

Two sets of primers were designed for the plc gene of C. perfringens, and the amplification efficiency and specificity of the primers. Selection of primers produces an amplified fragment on which the probe is designed. The probe was combined with the lateral flow biosensor (LFB). The reaction time and temperature of RPA-LFB assay were optimized, and the sensitivity of the assay was assessed. Several common foodborne pathogens were selected to test the specificity of the established method. Chicken and milk samples were artificially inoculated with different concentrations (1 × 102 CFU/mL to 1 × 106 CFU/mL) of C. perfringens, and the detection efficiency of RPA-LFB method and PCR method was compared. RPA-LFB can be completed in 20 min and the results can be read visually by the LFB test strips. The RPA-LFB has acceptable specificity and the lowest detection limit of 100 pg./μL for nucleic acid samples. It was able to stably detect C. perfringens contamination in chicken and milk at the lowest concentration of 1 × 104 CFU/mL and 1 × 103 CFU/mL, respectively.

Conclusion

In conclusion, RPA-LFB is specific and sensitive. It is a rapid, simple and easy-to-visualize method for the detection of C. perfringens in food and is suitable for use in field testing work.

Enhancing food safety in soybean fermentation through strategic implementation of starter cultures

Fermented soybean products have played a significant role in Asian diets for a long time. Due to their diverse flavours, nutritional benefits, and potential health-promoting properties, they have gained a huge popularity globally in recent years. Traditionally, soybean fermentation is conducted spontaneously, using microorganisms naturally present in the environment, or inoculating with traditional starter cultures. However, many potential health risks are associated with consumption of these traditionally fermented soybean products due to the presence of food pathogens, high levels of biogenic amines and mycotoxins. The use of starter culture technology in fermentation has been well-studied in recent years and confers significant advantages over traditional fermentation methods due to strict control of the microorganisms inoculated. This review provides a comprehensive review of microbial safety and health risks associated with consumption of traditional fermented soybean products, and how adopting starter culture technology can help mitigate these risks to ensure the safety of these products.

Detection of Clostridium perfringens Using Novel Methods Based on Recombinase-Aided Amplification Assay-Assisted CRISPR/Cas12a System

Clostridium perfringens is a highly versatile pathogen of humans and animals. Rapid and sensitive detection methods for C. perfringens are urgently needed for the timely implementation of control. In this study, to provide novel promising methods for the detection of C. perfringens, two rapid, sensitive, and instrument-free C. perfringens detection methods based on recombinase-aided amplification (RAA) assay and clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 12a (CRISPR/Cas12a) system were developed depending on fluorescence signal (RAA-CRISPR/Cas12a-FL) and lateral flow strip (RAA-CRISPR/Cas12a-LFS), respectively. The limit of detection of the RAA-CRISPR/Cas12a-FL and RAA-CRISPR/Cas12a-LFS methods is 2 copies and 20 copies of C. perfringens genomic DNA per reaction, respectively, and the whole process can be completed in 1 hr. Moreover, these two methods show no cross-reactivity with nontarget bacteria, which were used as a negative control to evaluate the specificity of two developed methods in the detection of C. perfringens and have 100% consistent with real-time polymerase chain reaction tests for 12 clinical samples collected from 2 Chinese Milu at Beijing Milu Ecological Research Center and 6 spiked samples from human blood and stool. Overall, the constructed C. perfringens detection methods, RAA-CRISPR/Cas12a-FL and RAA-CRISPR/Cas12a-LFS, have great potential as a novel detection scheme for the early diagnosis of C. perfringens infection in humans and animals.

Conventional and advanced detection techniques of foodborne pathogens: A comprehensive review

Foodborne pathogens are a major public health concern and have a significant economic impact globally. From harvesting to consumption stages, food is generally contaminated by viruses, parasites, and bacteria, which causes foodborne diseases such as hemorrhagic colitis, hemolytic uremic syndrome (HUS), typhoid, acute, gastroenteritis, diarrhea, and thrombotic thrombocytopenic purpura (TTP). Hence, early detection of foodborne pathogenic microbes is essential to ensure a safe food supply and to prevent foodborne diseases. The identification of foodborne pathogens is associated with conventional (e.g., culture-based, biochemical test-based, immunological-based, and nucleic acid-based methods) and advances (e.g., hybridization-based, array-based, spectroscopy-based, and biosensor-based process) techniques. For industrial food applications, detection methods could meet parameters such as accuracy level, efficiency, quickness, specificity, sensitivity, and non-labor intensive. This review provides an overview of conventional and advanced techniques used to detect foodborne pathogens over the years. Therefore, the scientific community, policymakers, and food and agriculture industries can choose an appropriate method for better results.

Molecular Diagnostic Tools Applied for Assessing Microbial Water Quality

Microbial water quality is of vital importance for human, animal, and environmental health. Notably, pathogenically contaminated water can result in serious health problems, such as waterborne outbreaks, which have caused huge economic and social losses. In this context, the prompt detection of microbial contamination becomes essential to enable early warning and timely reaction with proper interventions. Recently, molecular diagnostics have been increasingly employed for the rapid and robust assessment of microbial water quality implicated by various microbial pollutants, e.g., waterborne pathogens and antibiotic-resistance genes (ARGs), imposing the most critical health threats to humans and the environment. Continuous technological advances have led to constant improvements and expansions of molecular methods, such as conventional end-point PCR, DNA microarray, real-time quantitative PCR (qPCR), multiplex qPCR (mqPCR), loop-mediated isothermal amplification (LAMP), digital droplet PCR (ddPCR), and high-throughput next-generation DNA sequencing (HT-NGS). These state-of-the-art molecular approaches largely facilitate the surveillance of microbial water quality in diverse aquatic systems and wastewater. This review provides an up-to-date overview of the advancement of the key molecular tools frequently employed for microbial water quality assessment, with future perspectives on their applications.

eDNA-based detection of the invasive crayfish Pacifastacus leniusculus in streams with a LAMP assay using dependent replicates to gain higher sensitivity

LAMP assays are becoming increasingly popular in the field of invasive species detection but are still underused in eDNA-based monitoring. Here, we propose a LAMP assay designed to detect the North American crayfish species Pacifastacus leniusculus in water samples from streams. The presence of P. leniusculus was detected through this new LAMP assay in all but one of the nine sites sampled. No correlation was found between ddPCR absolute concentration measurements and the number of LAMP-positive technical replicates. However, we showed that using dependent technical replicates could significantly enhance the detection sensitivity of the LAMP assay. Applied to other assays, it could improve sensitivity and thus allow for a more efficient use of eDNA-based LAMP assays for invasive species detection in aquatic ecosystems.

Dual-mode sensor based on the synergy of magnetic separation and functionalized probes for the ultrasensitive detection of Clostridium perfringens

Clostridium perfringens is an important foodborne pathogen, which has caused serious public health problems worldwide. So, there is an urgent need for rapid and ultrasensitive detection of C. perfringens. In this paper, a dual-mode sensing platform using the synergy between fluorescent and electrochemical signals for Clostridium perfringens detection was proposed. An electrochemical aptasensor was constructed by a dual-amplification technology based on a DNA walker and hybridization chain reaction (HCR). When the C. perfringens genomic DNA was present, it specifically bonded with FAM-labeled aptamer which triggered the DNA walker on hairpin DNA (hDNA) tracks to start the synthesis of double-stranded DNA. HCR occurred subsequently and produced long-chain DNA to absorb more methylene blue (MB). In this cycle, the fluorescent signals of released FAM-labeled aptamer could also be detected. The synergistic effects of MB and FAM significantly improved the sensitivity and accuracy of the dual-mode sensor. As a result, the biosensor displayed an excellent analytical performance for C. perfringens at a concentration of 1 to 10⁸ CFU g⁻¹. A minimum concentration of 1 CFU g⁻¹ and good accuracy were detected in real samples. The proposed ultrasensitive detection method for detecting C. perfringens in food showed great potential in controlling foodborne diseases.

Clostridium perfringens is an important foodborne pathogen, which has caused serious public health problems worldwide.

Rapid and simultaneous detection of Campylobacter spp. and Salmonella spp. in chicken samples by duplex loop-mediated isothermal amplification coupled with a lateral flow biosensor assay

Development of a simple, rapid and specific assay for the simultaneous detection of Campylobacter spp. and Salmonella spp. based on duplex loop-mediated isothermal amplification (d-LAMP), combined with lateral-flow biosensor (LFB) is reported herein. LAMP amplicons of both pathogens were simultaneously amplified and specifically differentiated by LFB. The specificity of the d-LAMP-LFB was evaluated using a set of 68 target and 12 non-target strains, showing 100% inclusivity and exclusivity. The assay can simultaneously detect Campylobacter and Salmonella strains as low as 1 ng and 100 pg genomic DNA per reaction, respectively. The lowest inoculated detection limits for Campylobacter and Salmonella species in artificially contaminated chicken meat samples were 103 CFU and 1 CFU per 25 grams, respectively, after enrichment for 24 h. Furthermore, compared to culture-based methods using field chicken meat samples, the sensitivity, specificity and accuracy of d-LAMP- LFB were 95.6% (95% CI, 78.0%-99.8%), 71.4% (95% CI, 29.0%-96.3%) and 90.0% (95% CI, 73.4%-97.8%), respectively. The developed d-LAMP-LFB assay herein shows great potentials for the simultaneous detection of the Campylobacter and Salmonella spp. and poses a promising alternative approach for detection of both pathogens with applications in food products.