Loop-mediated isothermal amplification assays for detecting Yersinia pseudotuberculosis in milk powders

Poly(indole-5-carboxylic acid)/reduced graphene oxide/gold nanoparticles/phage-based electrochemical biosensor for highly specific detection of Yersinia pseudotuberculosis

Yersinia pseudotuberculosis is an enteric bacterium causing yersiniosis in humans. The existing Yersinia pseudotuberculosis detection methods are time-consuming, requiring a sample pretreatment step, and are unable to discriminate live/dead cells. The current work reports a phage-based electrochemical biosensor for rapid and specific detection of Yersinia pseudotuberculosis. The conductive poly(indole-5-carboxylic acid), reduced graphene oxide, and gold nanoparticles are applied for surface modification of the electrode. They possess ultra-high redox stability and retain 97.7% of current response after performing 50 consecutive cycles of cyclic voltammetry.The specific bacteriophages vB_YepM_ZN18 we isolated from hospital sewage water were immobilized on modified electrodes by Au-NH₂ bond between gold nanoparticles and phages. The biosensor fabricated with nanomaterials and phages were utilized to detect Yersinia pseudotuberculosis successfully with detection range of 5.30 × 10² to 1.05 × 10⁷ CFU mL^-1, detection limit of 3 CFU mL^-1, and assay time of 35 min. Moreover, the biosensor can specifically detect live Yersinia pseudotuberculosis without responding to phage-non-host bacteria and dead Yersinia pseudotuberculosis cells. These results suggest that the proposed biosensor is a promising tool for the rapid and selective detection of Yersinia pseudotuberculosis in food, water, and clinical samples.

Detection of Yersinia enterocolitica in milk powders by cross-priming amplification combined with immunoblotting analysis

Yersinia enterocolitica (Y. enterocolitica) is frequently isolated from a wide variety of foods and can cause human yersiniosis. Biochemical and culture-based assays are common detection methods, but require a long incubation time and easily misidentify Y. enterocolitica as other non-pathogenic Yersinia species. Alternatively, cross-priming amplification (CPA) under isothermal conditions combined with immunoblotting analysis enables a more sensitive detection in a relatively short time period. A set of specific displacement primers, cross primers and testing primers was designed on the basis of six specific sequences in Y. enterocolitica 16S-23S rDNA internal transcribed spacer. Under isothermal condition, amplification and hybridization were conducted simultaneously at 63°C for 60 min. The specificity of CPA was tested for 96 different bacterial strains and 165 commercial milk powder samples. Two red lines were developed on BioHelix Express strip for all of the Y. enterocolitica strains, and one red line was shown for non-Y. enterocolitica strains. The limit of detection of CPA was 10(0)fg for genomic DNA (1000 times more sensitive than PCR assay), 10(1) CFU/ml for pure bacterial culture, and 10(0) CFU per 100 g milk powder with pre-enrichment at 37°C for 24 h. CPA combined with immunoblotting analysis can achieve highly specific and sensitive detection of Y. enterocolitica in milk powder in 90 min after pre-enrichment.