Multiplex Detection of Five Canine Viral Pathogens for Dogs as Laboratory Animals by the Luminex xTAG Assay

Laboratory tools for the direct detection of bacterial respiratory infections and antimicrobial resistance: a scoping review

Rapid laboratory tests are urgently required to inform antimicrobial use in food animals. Our objective was to synthesize knowledge on the direct application of long-read metagenomic sequencing to respiratory samples to detect bacterial pathogens and antimicrobial resistance genes (ARGs) compared to PCR, loop-mediated isothermal amplification, and recombinase polymerase amplification. Our scoping review protocol followed the Joanna Briggs Institute and PRISMA Scoping Review reporting guidelines. Included studies reported on the direct application of these methods to respiratory samples from animals or humans to detect bacterial pathogens ±ARGs and included turnaround time (TAT) and analytical sensitivity. We excluded studies not reporting these or that were focused exclusively on bioinformatics. We identified 5,636 unique articles from 5 databases. Two-reviewer screening excluded 3,964, 788, and 784 articles at 3 levels, leaving 100 articles (19 animal and 81 human), of which only 7 studied long-read sequencing (only 1 in animals). Thirty-two studies investigated ARGs (only one in animals). Reported TATs ranged from minutes to 2 d; steps did not always include sample collection to results, and analytical sensitivity varied by study. Our review reveals a knowledge gap in research for the direct detection of bacterial respiratory pathogens and ARGs in animals using long-read metagenomic sequencing. There is an opportunity to harness the rapid development in this space to detect multiple pathogens and ARGs on a single sequencing run. Long-read metagenomic sequencing tools show potential to address the urgent need for research into rapid tests to support antimicrobial stewardship in food animal production.

Development of a bead-based assay for detection and differentiation of field strains and four vaccine strains of type 2 porcine reproductive and respiratory syndrome virus (PRRSV-2) in the USA

Porcine reproductive and respiratory syndrome (PRRS) remains one of the most economically devastating diseases in swine population in the United States of America. Due to high mutation rate of the PRRS virus (PRRSV) genome, it is difficult to develop an accurate diagnostic assay with high strain coverage. Differentiation of field strains from the four vaccines that have been used in the USA, namely Ingelvac PRRS MLV, Ingelvac ATP, Fostera PRRS and Prime Pac PRRS, adds an additional challenge. It is difficult to use current real-time PCR systems to detect and differentiate the field strains from the vaccine strains. Luminex xTAG technology allows us to detect more molecular targets in a single reaction with a cost similar to a single real-time PCR reaction. By analysing all available 678 type 2 PRRSV (PRRSV-2) complete genome sequences, including the 4 vaccine strains, two pairs of detection primers were designed targeting the conserved regions of ORF4-ORF7, with strain coverage of 98.8% (670/678) based on in silico analysis. The virus strains sharing ≥98% identity of the complete genomes with the vaccine strains were considered vaccine or vaccine-like strains. One pair of primers for each vaccine strain were designed targeting the nsp2 region. In silico analysis showed the assay matched 94.7% (54/57) of Ingelvac PRRS^® MLV (MLV) strain and the MLV-like strains, and 100% of the other three vaccine strains. Analytical sensitivity of the Luminex assay was one to two logs lower than that of the reverse transcription real-time PCR assay. Evaluated with 417 PRRSV-2 positive clinical samples, 95% were detected by the Luminex assay. Compared to ORF5 sequencing results, the Luminex assay detected 92.4% (73/79) of MLV strains, 78.3% (18/23) of Fostera strains and 50% (2/4) of ATP strains. None of the 472 samples were the Prime Pac strain tested by either ORF5 sequencing or the Luminex assay.

Development and evaluation of a Luminex xTAG assay for sulfonamide resistance genes in Escherichia coli and Salmonella isolates

Clinically occurring sulfonamide resistance in gram-negative bacteria is codified by several sul genes, mostly associated with the mobilized genetic elements named integrons, and integrons are frequently found in plasmids. There are four sul genes (sul1, sul2, sul3 and sul4) that encode resistance to sulfonamides. The aim of the present study was to develop a bead-based xTAG assay for the simultaneous detection of all four sul genes and related Class 1 integrons (int1) in Escherichia coli and Salmonella isolates. The limits of detection ranged from 10 to 1000 copies/μL of input purified plasmid DNA. Forty-one bacterial isolates from clinical samples were examined using the newly developed xTAG assay and also by conventional PCR to determine the relative performance of each. The results obtained by xTAG assay showed higher detection rates and accuracy for sul genes than conventional PCR. It indicated that the xTAG-multiplex PCR is a convenient method for rapid identification of sul genes.