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Problems with serological cross-reactivity have led to development of a number of PCRs (individual and multiplex) for molecular typing of Actinobacillus pleuropneumoniae , the causative agent of porcine pleuropneumonia. Most of these assays were developed for detection of specific amplicons within capsule biosynthetic genes before the availability of complete sequences for the different serovars. Here we describe comparative analysis of the complete capsular loci for all 18 serovars of A. pleuropneumoniae , and development of two multiplex PCRs for comprehensive capsule typing of this important pig pathogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Identification of A. pleuropneumoniae serovar 19 type II capsule locus. • Serovar 19 isolates are biovar 1, encode ApxII and ApxIV toxins, and have either a serogroup 3/6/8/15 or 4/7 O-Ag locus. • Reformulation of two mPCRs for unequivocal capsule typing of all known A. pleuropneumoniae serovars. Two serologically and molecularly non-typeable isolates of the porcine lung pathogen Actinobacillus pleuropneumoniae have been identified from diseased swine in two different continents. Genome sequencing was carried out to identify their diagnostically relevant genotypes. Both isolates are biovar 1 and encode genes for production of ApxIV and ApxII (apxIICA structural genes, and apxIBD export genes). They both possess the same novel type II capsule locus (most similar to serovar 1, but with two capsule genes not previously found in A. pleuropneumoniae) but differ in their O-Ag loci. Strain 7213384-1 from Denmark, which we propose as the reference strain for serovar 19, has a serogroup 3/6/8/15 O-Ag locus; the Canadian isolate A08-013 has a serogroup 4/7 O-Ag locus. We have expanded the second of our two previously described A. pleuropneumoniae mPCRs to include capsule gene-specific primers for definitive detection of serovars 13–14 and 16–19. [ABSTRACT FROM AUTHOR]