A “pathotyping” multiplex PCR for Haemophilus parasuis: a tool for the prediction of virulence

word count 225 (Max 250) 34 Haemophilus parasuis is a diverse bacterial species found in the upper respiratory 35 tract of pigs that can also cause Glässer’s disease and pneumonia. A previous pan36 genome study of H. parasuis identified 48 genes that were associated with clinical 37 disease. Here we describe the development of a generalised linear model (termed a 38 pathotyping model) to predict the potential virulence of isolates of H. parasuis, based 39 on a subset of 10 genes from the pan-genome. A multiplex PCR (mPCR) was 40 constructed based on these genes, the results of which were entered into the 41 pathotyping model to yield a prediction of virulence. This new diagnostic mPCR was 42 tested on 143 field isolates of H. parasuis that had previously been whole-genome 43 sequenced and a further 84 isolates from the UK from cases of H. parasuis-related 44 disease in pigs collected between 2013 and 2014. The combination of the mPCR and 45 on A uust 2, 2017 by gest ht://jcm .sm .rg/ D ow nladed fom the pathotyping model predicted the virulence of an isolate with 78% accuracy for the 46 original isolate collection, and 90% for the additional isolate collection, providing an 47 overall accuracy of 83% (81% sensitivity and 93% specificity) when compared with 48 the ‘current standard’ of detailed clinical meta-data. This new pathotyping assay has 49 the potential to aid surveillance and disease control in addition to serotyping data. 50