Development of loop-mediated isothermal method and comparison with conventional PCR assay for rapid on spot identification of tissue of cattle origin.

Loop-mediated isothermal amplification (LAMP) is a diagnostic method for meat speciation with rapid and minimal equipment requirements. In this study, we developed cattle-specific tube-based LAMP assays targeting mitochondrial Cyt b gene sequence, compared with conventional PCR assay for specificity, sensitivity, and validation of the assay was made. The LAMP reaction was carried at 64 °C for 45 min, and results were confirmed by SYBR Green I dye and agarose gel-electrophoresis. The specificity of the assays was cross-tested with DNA of buffalo, goat, sheep, and pork. The amplification was observed with samples from cattle only without cross-reactivity with other meat species. The analytical sensitivity of LAMP and PCR method for cattle DNA detection was 0.0001 ng and 1 ng, respectively. Repeatability of the assay was achieved on samples from known/blind and admixture meat with other than cattle at the relative percentage of 20%, 10%, 5%, and 1%. The study concluded that the developed assay can be easily employed for the rapid identification of tissue of cattle origin in meat and meat products in low resource areas.

On point identification of species origin of food animals by recombinase polymerase amplification-lateral flow (RPA-LF) assay targeting mitochondrial gene sequences.

The present study was aimed to develop and standardize Recombinase polymerase amplification-lateral flow (RPA-LF) assays for on point identification of species origin of food animals viz: cattle, buffalo and pig. Species specific RPA primers sets for cattle, buffalo and pig were designed by homology comparisons of the sequences of mitochondrial cytochrome b gene and d-loop region from common food species viz: cattle, buffalo, sheep, goat, pig and chicken. The RPA assays for designed primers sets were optimized using the reaction components from Twist Amp basic kit and instructions in its manual. Endpoint detection of species specific amplified RPA products were made by gel electrophoresis and designed species specific RPA-LFA strips. The developed assays were evaluated for their specificity, diagnostic sensitivity, and validated on coded samples and binary meat admixtures with relative percentage of 20, 10, 5 & 1% target species. The developed RPA assays resulted in amplification of DNA template exclusively of cattle, buffalo and pig origin to product sizes of 294, 405 and 283 bp respectively. The diagnostic sensitivities of developed assays were up to 10 pg of genomic DNA and highly correlated with species specific PCR assays taken as gold standard. Developed species specific RPA assays also identified the target species in coded samples and binary meat admixture up to 1%.

Paper-based loop-mediated isothermal amplification and lateral flow (LAMP-LF) assay for identification of tissues of cattle origin.

The present study was made with the objectives of development and standardization of cattle specific paper-based loop-mediated isothermal amplification cum lateral flow assay (LAMP-LFA), as a Point-of-care test (POCT) for identification of tissue of cattle origin. The components of standardized LAMP reaction utilizing cattle specific primer sets were lyophilized over paper buttons, identified best as the carrier of LAMP reagents. Based on probable LAMP amplicon, a pair of probes was designed, tagged and its hybridization with the amplified product of paper LAMP reaction was optimized. The components of lateral flow assay for detection of probe hybridized LAMP products were standardized. Analysis of successful amplification was made by using HNB dye, LAMP-LFA strip, and also by the typical ladder-like pattern on gel electrophoresis. The assay was found highly specific for cattle with an analytical sensitivity of 0.1 pg of absolute DNA. Laboratory validation carried out on samples from different individuals of cattle, coded samples, binary meat admixture, and heat-processed cattle tissues substantiated the accuracy of the assay. Comparison with pre-standardized species-specific PCR assay taken as gold standards revealed 100% conformity. The field utility of the developed assay was further established by its compatibility with the commercial kit eliminating the lengthy DNA extraction step and storage stability of LAMP reagent carrier buttons for 4 months under refrigeration. Thus, the developed assay capable of the result within 3 h in resource-limited settings can be used as POCT for identification of tissue of cattle origin.

Species-specific loop-mediated isothermal amplification (LAMP) assay for identification of tissue of cattle origin by targeting mitochondrial gene sequences.

The present study was carried out with the objective of development of species-specific loop-mediated isothermal amplification (LAMP) assay for identification of tissue of cattle origin. The cattle-specific LAMP primer set was designed by targeting mitochondrial D-loop gene. The conditions for LAMP reaction for amplification of template DNA from cattle using designed cattle-specific primer set were optimized for the components of mixture and temperature of reaction. Amplified products were analysed using SYBR Green I dye and by agarose gel electrophoresis. The developed species-specific LAMP assay was evaluated for its specificity, sensitivity and validated in laboratory on samples from known, coded, binary meat admixture with other than cattle at relative percentage of 20%, 10%, 5% and 1%, Phire tissue direct PCR master mix treated tissues of cattle and on species-specific polymerase chain reaction assay positive samples. The developed LAMP assay using self-designed primer set was highly specific, amplifying the DNA template exclusively from cattle tissue under the optimized LAMP reaction conditions. The sensitivity assay using serially diluted DNA templates revealed lowest level of detection as 0.01 ng of absolute DNA from target species. Laboratory validation substantiated the accuracy of assay in known/unknown (coded) samples and up to the 1% level of admixture in binary meat sample. DNA present in supernatant of Phire Animal tissue kit treated samples were also amplified successfully eliminating the extra step of extraction of genomic DNA. The developed assays exhibited comparable results with previously established species-specific PCR assay taken as gold standards. Thus, it was concluded that developed species-specific loop-mediated isothermal amplification assay was effective in identification of tissue of cattle origin.