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.

Visual loop-mediated isothermal amplification (LAMP) for the rapid diagnosis of Enterocytozoon hepatopenaei (EHP) infection

The emerging microsporidian parasite Enterocytozoon hepatopenaei (EHP), the causative agent of hepatopancreatic microsporidiosis, has been widely reported in shrimp-farming countries. EHP infection can be detected by light microscopy observation of spores (1.7 × 1 μm) in stained hepatopancreas (HP) tissue smears, HP tissue sections, and fecal samples. EHP can also be detected by polymerase chain reaction (PCR) targeting the small subunit (SSU) ribosomal RNA (rRNA) gene or the spore wall protein gene (SWP). In this study, a rapid, sensitive, specific, and closed tube visual loop-mediated isothermal amplification (LAMP) protocol combined with FTA cards was developed for the diagnosis of EHP. LAMP primers were designed based on the SSU rRNA gene of EHP. The target sequence of EHP was amplified at constant temperature of 65 °C for 45 min and amplified LAMP products were visually detected in a closed tube system by using SYBR™ green I dye. Detection limit of this LAMP protocol was ten copies. Field and clinical applicability of this assay was evaluated using 162 field samples including 106 HP tissue samples and 56 fecal samples collected from shrimp farms. Out of 162 samples, EHP could be detected in 62 samples (47 HP samples and 15 fecal samples). When compared with SWP-PCR as the gold standard, this EHP LAMP assay had 95.31% sensitivity, 98.98% specificity, and a kappa value of 0.948. This simple, closed tube, clinically evaluated visual LAMP assay has great potential for diagnosing EHP at the farm level, particularly under low-resource circumstances.