Development and evaluation of isothermal amplification assay for the rapid and sensitive detection of Clostridium perfringens from chevon

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.

Rapid and visual detection of Shiga-toxigenic Escherichia coli (STEC) in carabeef meat harnessing loop-mediated isothermal amplification (LAMP)

Shiga toxigenic E. coli are important foodborne zoonotic pathogens. The present study was envisaged to standardize loop-mediated isothermal amplification assays targeting stx1 and stx2 genes for rapid and visual detection of STEC and compare its sensitivity with PCR. The study also assessed the effect of short enrichment on the detection limit of LAMP and PCR. The developed LAMP assays were found to be highly specific. Analytical sensitivity of LAMP was 94 fg/µLand 25.8 fg/µL for stx-1 and stx-2 while LOD of 5 CFU/g of carabeef was measured after 6-12 h enrichment. The study highlights the importance of short (6-12 h) enrichment for improving the sensitivity of LAMP. The entire detection protocol could be performed within 9 h yielding results on the same day. The developed LAMP assays proved to be a handy and cost-effective alternative for screening STEC contamination in meat.

Identification of the novel potential pathogen Trueperella pecoris with interspecies significance by LAMP diagnostics

Trueperella pecoris was described as a new species of the genus Trueperella in 2021 and might be pathogenic to various animal species. However, the lack of a suitable diagnostic test system stands in the way of epidemiological surveys to clarify possible causalities. In this study, a Loop-mediated Isothermal Amplification (LAMP) assay was developed and validated that was highly specific for T. pecoris. The assay provided an analytical sensitivity of 0.5 pg/25 µL and showed 100% inclusivity and exclusivity for 11 target and 33 non-target strains, respectively. Three different DNA extraction methods were evaluated to select the most LAMP-compatible method for cell disruption in pure and complex samples. Using an on-site applicable single-buffer DNA extraction with additional heating, the cell-based detection limit was 2.3 CFU/reaction. Finally, the LAMP assay was validated by means of artificially contaminated porcine lung tissue samples in which minimal microbial loads between 6.54 and 8.37 × 103 CFU per swab sample were detectable. The LAMP assay established in this study represents a suitable diagnostic procedure for identifying T. pecoris in clinical specimens and will help to collect epidemiological data on the pathogenicity of this species.

Isothermal nucleic acid amplification and its uses in modern diagnostic technologies

Nucleic acids are prominent biomarkers for diagnosing infectious pathogens using nucleic acid amplification techniques (NAATs). PCR, a gold standard technique for amplifying nucleic acids, is widely used in scientific research and diagnosis. Efficient pathogen detection is a key to adequate food safety and hygiene. However, using bulky thermal cyclers and costly laboratory setup limits its uses in developing countries, including India. The isothermal amplification methods are exploited to develop miniaturized sensors against viruses, bacteria, fungi and other pathogenic organisms and have been applied for in situ diagnosis. Isothermal amplification techniques have been found suitable for POC techniques and follow WHO's ASSURED criteria. LAMP, NASBA, SDA, RCA and RPA are some of the isothermal amplification techniques which are preferable for POC diagnostics. Furthermore, methods such as WGA, CPA, HDA, EXPAR, SMART, SPIA and DAMP were introduced for even more accuracy and robustness. Using recombinant polymerases and other nucleic acid-modifying enzymes has dramatically broadened the detection range of target pathogens under the scanner. The coupling of isothermal amplification methods with advanced technologies such as CRISPR/Cas systems, fluorescence-based chemistries, microfluidics and paper-based sensors has significantly influenced the biosensing and diagnosis field. This review comprehensively analyzed isothermal nucleic acid amplification methods, emphasizing their advantages, disadvantages and limitations.

Prevalence, molecular characterization, and antimicrobial resistance profile of Clostridium perfringens from India: A scoping review

Clostridium perfringens is one of the most important foodborne pathogens that causes histotoxic diseases and intestinal infections in both humans and animals. The present scoping review has been designed to analyze the literature published during 2000-2021 from India on the prevalence, molecular characterization, and antimicrobial resistance profile of C. perfringens isolates recovered from humans, animals, animal-based foods, and associated environmental samples. The peer-reviewed articles retrieved from four electronic databases (Google Scholar, PubMed, Science Direct, and Web of Science) were assessed using PRISMA-ScR guidelines. A total of 32 studies from India were selected on the basis of their relevance and inclusion criteria. The overall prevalence of C. perfringens among domestic animals having history of clinical symptoms and among healthy animals was found to be 65.8% (508/772) and 42.8% (493/1152), respectively. The pathogen was also detected in clinically affected wild animals (75%), healthy wild animals (35.4%), and captive birds (24.5%). The detection of C. perfringens among poultry having necrotic enteritis and among healthy birds was found to be 66.8% (321/480) and 25.6% (80/312), respectively. The detection of pathogen among animal-based foods (i.e., meat, milk, and fish and their products) and environmental samples depicted a prevalence of 20.8% (325/1562) and 30.2% (23/76), respectively. However, the prevalence of C. perfringens among humans having history of diarrhea and among healthy humans was found to be 25% (70/280) and 23.2% (36/155), respectively. The genotyping of C. perfringens isolates revealed that toxin type A was found to be the most prevalent genotype. Along with the alpha toxin gene (cpa), beta (cpb), epsilon (etx), iota (itx), enterotoxin (cpe), beta-2 toxin (cpb2), and NetB (netB) toxins were also detected in different combinations. Antimicrobial resistance profile of C. perfringens isolates recovered from different sources demonstrated that the highest resistance was detected against sulphonamides (76.8%) and tetracycline (41.3%) by phenotypic and genotypic detection methods, respectively. Comprehensive scientific studies covering different geographical areas at the human-animal-environment interface are crucial to generalize the real magnitude of C. perfringens-associated problem in India and for establishing a reliable database.

Recent advances in loop-mediated isothermal amplification (LAMP) for rapid and efficient detection of pathogens

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Significance of LAMP method in rapid disease diagnosis is highlighted.

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Different detection methods for amplicon visualization are explained.

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Advancements in LAMP technique for disease identification are summarized.

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Trends in development of LAMP disease diagnosis are discussed.

Loop-mediated isothermal amplification (LAMP) method has been demonstrated to bea reliable and robust method for detection and identification of viral and microbial pathogens. LAMP method of amplification, coupled with techniques for easy detection of amplicons, makes a simple-to-operate and easy-to-read molecular diagnostic tool for both laboratory and on-field settings. Several LAMP-based diagnostic kits and assays have been developed that are specifically targeted against a variety of pathogens. With the growing needs of the demanding molecular diagnostic industry, many technical advances have been made over the years by combining the basic LAMP principle with several other molecular approaches like real-time detection, multiplex methods, chip-based assays.This has resulted in enhancing thethe sensitivity and accuracy of LAMP for more rigorous and wide-ranging pathogen detection applications. This review summarizes the current developments in LAMP technique and their applicability in present and future disease diagnosis.

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.

Development of novel visual detection methodology for Salmonella in meat using saltatory rolling circle amplification

AIM

The aim of this study was to develop a saltatory rolling circle amplification (SRCA) assay for rapid, simple and visual detection of Salmonella in meat.

METHODS AND RESULTS

Saltatory rolling circle amplification assay was established using simple PCR primers targeting the invA gene of Salmonella enterica. The specificity of the SRCA assay was determined using 28 Salmonella and 15 non-Salmonella strains. The analytical sensitivity of the developed SRCA, conventional and real-time PCR assays were 70 fg, 7 pg and 700 fg S. enterica DNA per tube, respectively. The limit of detection (LoD) of the SRCA assay was 40 CFU per gram of meat without enrichment and 4 CFU per gram after including 6 h brief enrichment step. The detection limits of 40 CFU per gram and 4 CFU per gram of meat were achieved within 165 min and 9 h, respectively (including DNA extraction). To assess the real-world relevance of the SRCA assay, it was used to screen Salmonella from the field pork samples (n = 82). The same samples were also tested with culture (ISO 6579: 2002) method, conventional and real-time PCR assays. Using the developed assay with 6-h enrichment step, it could give accurate results as that of the culture method.

CONCLUSIONS

The results of this study showed that the SRCA assay is a rapid, simple, sophisticated equipment-free and user-friendly method for accurate detection of Salmonella in meat foods. To our information, this is the first study to deploy SRCA assay for screening foods for Salmonella.

SIGNIFICANCE AND IMPACT OF THE STUDY

The developed SRCA assay is cost-effective, easy-to-perform and equipment-free; therefore, it has the potential to replace other molecular detection methods for regular screening of Salmonella in foods in field laboratories.

A novel in situ methodology for visual detection of Clostridium perfringens in pork harnessing saltatory rolling circle amplification

Clostridium perfringens (C. perfringens), a prolific toxin-producing anaerobe is an important foodborne pathogen with a huge public health concern. Rapid and on-site detection of C. perfringens is of specific importance in developing countries. In the present study, saltatory rolling circle amplification (SRCA) assay was developed for culture-independent, rapid and visual detection of C. perfringens and evaluated in meat with pork as a model. The specificity of the SRCA assay was ascertained by using 62 C. perfringens and 18 non- C. perfringens strains. The analytical sensitivity of the developed SRCA, conventional and real-time PCR assays were 80 fg, 800 fg and 800 fg DNA per tube, respectively. The limit of detection of the SRCA assay was 80 CFU/g of pork in the absence of enrichment and 8 CFU/g after short enrichment of 6 h. The detection limits of 80 CFU/g and 8 CFU/g of pork were attained within 120 min and 8 h, respectively. Real-world or field relevancy of the developed assay was evaluated by screening 82 raw and processed pork samples. As the developed assay is simple, user-friendly, cost-effective and sophisticated-equipment free, it would be more suitable for on-site testing of C. perfringens in foods. To our information, this is the first report to apply SRCA for the detection of C. perfringens.

Development of a novel polymerase spiral reaction (PSR) assay for rapid and visual detection of Clostridium perfringens in meat

C. perfringens is a widespread foodborne pathogen and one of the major concerns in the meat industry. There is a need for a simple, rapid and equipment free detection system for C. perfringens as conventional anaerobic culture method is labour and resource intensive. Here, we applied a novel polymerase spiral reaction phenomenon to develop and evaluate an assay for effortless and visual detection of C. perfringens in meat foods employing pork as a representative model. Specificity of the assay was determined using 51 C perfringens and 20 non- C. perfringens strains. Analytical sensitivity of the developed test was 80 fg DNA per tube indicating 100 times more sensitivity than end-point PCR assay. The detection limits were 980 CFU/g and 9.8 × 10⁴ CFU/g of pork for PSR and PCR assays, respectively. The operation time of the PSR assay including DNA extraction was 120 min. The developed PSR assay was accurate and effective in comparison to culture method, in detecting C. perfringens in 38 of 74 pork samples. Therefore the specificity, sensitivity, negative predictive value, positive predictive value and accuracy rate of the developed PSR assay were 100%. The developed PSR assay is easy to perform, rapid, affordable, permitting sophisticated-equipment free amplification and naked eye interpretation. This is the initial report in which the PSR assay was optimized for the detection of C. perfringens.

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

Clostridium perfringens is a key anaerobic pathogen causing food poisoning. Definitive detection by standard culture method is time-consuming and labor intensive. Current rapid commercial test kits are prohibitively expensive. It is thus necessary to develop rapid and cost-effective detection tool. Here, loop-mediated isothermal amplification (LAMP) in combination with a lateral-flow biosensor (LFB) was developed for visual inspection of C. perfringens-specific cpa gene. The specificity of the developed test was evaluated against 40 C. perfringens and 35 other bacterial strains, which showed no cross-reactivity, indicating 100% inclusivity and exclusivity. LAMP-LFB detection limit for artificially contaminated samples after enrichment for 16 h was 1-10 CFU/g sample, which was comparable to the commercial real-time PCR kit. The detection performance of LAMP-LFB was also compared to culture-based method using 95 food samples, which revealed the sensitivity (SE), specificity (SP) and Cohen's kappa coefficient (κ) of 88.0% (95% CI, 75.6%-95.4%), 95.5% (95% CI, 84.8%-99.4%) and 0.832 (95% CI, 0.721-0.943), respectively. Area under the receiver operating characteristic (ROC) curve was 0.918 (95% CI, 0.854-0.981), indicating LAMP-LFB as high relative accuracy test. In conclusion, LAMP-LFB assay is a low-cost qualitative method and easily available for routine detection of C. perfringens in food samples, which could serve as an alternative to commercial test kit.

Recent trends in the utilization of LAMP for the diagnosis of viruses, bacteria, and allergens in food

Foodborne diseases are becoming major scientific struggles for both developing and developed countries. Most foodborne infections are caused by microbial pathogens such as bacteria, viruses, and other food allergens. Hence early and accurate diagnosis of these foodborne pathogens is always preferable. To satisfy these concerns, plenty of isothermal amplification methodologies such as rolling circle amplification (RCA), helicase-dependent amplification (HDA), and recombinase polymerase amplification (RPA) have been developed. Among these, loop-mediated isothermal amplification (LAMP) is a widely usable, potential, and recognizable amplification technique achieved at a constant temperature around 60°C within 30–60 min by using only one kind of enzyme. As a robust gene amplification technique, it can be employed for the detection of bacteria, viruses, and other related food allergens. This technique has its own merits such as cost-effectiveness, facile manufacturing procedure, and consistency. In this chapter, we emphasize recent trends in designing the techniques, challenges, and the future prospects of LAMP in the detection of foodborne pathogens. These effective pathogen detection methods may offer potential benefits compared with existing conventional methods.

Prevalence, molecular typing and antibiotic resistance of Clostridium perfringens in free range ducks in Northeast India

This study reports faecal prevalence of Clostridium perfringens in free range ducks in North East India for the first time. We also report C. perfringens type A carrying cpb2 and cpe and type C carrying cpb2 and cpe strains in these ducks. Notably, a high prevalence (17.5%) of enterotoxin carrying C. perfringens strains and low antimicrobial resistance were observed.

From hazard analysis to risk control using rapid methods in microbiology: A practical approach for the food industry

The prevention of foodborne diseases is one of the main objectives of health authorities. To this effect, analytical techniques to detect and/or quantify the microbiological contamination of foods prior to their release onto the market are required. Management and control of foodborne pathogens have generally been based on conventional detection methodologies, which are not only time-consuming and labor-intensive but also involve high consumable materials costs. However, this management perspective has changed over time given that the food industry requires efficient analytical methods that obtain rapid results. This review covers the historical context of traditional methods and their passage in time through to the latest developments in rapid methods and their implementation in the food sector. Improvements and limitations in the detection of the most relevant pathogens are discussed from a perspective applicable to the current situation in the food industry. Considering efforts that are being done and recent developments, rapid and accurate methods already used in the food industry will be also affordable and portable and offer connectivity in near future, which improves decision-making and safety throughout the food chain.

Simple Visualized Detection Method of Virulence-Associated Genes of Vibrio cholerae by Loop-Mediated Isothermal Amplification

Vibrio cholerae is a leading waterborne pathogenic bacterium worldwide. It can cause human cholera that is still pandemic in developing nations. Detection of V. cholerae contamination in drinking water and aquatic products is imperative for assuring food safety. In this study, a simple, sensitive, specific, and visualized method was developed based on loop-mediated isothermal amplification (LAMP) (designated sssvLAMP) to detect virulence-associated (ctxA, tcpA, hapA, mshA, pilA, and tlh) and species-specific (lolB) genes of V. cholerae. Three pairs of oligonucleotide primers (inner, outer, and loop primers) were designed and or synthesized to target each of these genes. The optimal conditions of the sssvLAMP method was determined, and one-step sssvLAMP reaction was performed at 65°C for 40 min. Positive results were simply read by the naked eye via color change (from orange to light green) under the visible light, or by the production of green fluorescence under the UV light (260 nm). The sssvLAMP method was more efficient in detecting 6.50 × 101-6.45 × 104-fold low number of V. cholerae cells, and more sensitive in V. cholerae genomic DNA (1.36 × 10-2-4.42 × 10-6 ng/reaction) than polymerase chain reaction (PCR) method. Among 52 strains of V. cholerae and 50 strains of non-target species (e.g., other Vibrios and common pathogens) examined, the sensitivity and specificity of the sssvLAMP method were 100% for all the target genes. Similar high efficiency of the method was observed when tested with spiked samples of water and aquatic products, as well as human stool specimens. Water from various sources and commonly consumed fish samples were promptly screened by this simple and efficient visualized method and diversified variation in the occurrence of the target genes was observed. V. cholerae strains could be mostly detected by the presence of hapA and tlh alone or in combination with other genes, indicating a variable risk of potentially pathogenic non-O1/O139 strains in edible food products. This novel LAMP method can be a promising tool to address the increasing need of food safety control of aquatic products.