Five Actinobacillus pleuropneumoniae strains isolated from pathological lesions of porcine pleuropneumonia in Hungary could not be assigned to any of the accepted 15 serovars. Using hyperimmune serum raised against these unty-pable-serovar A. pleuropneumoniae strains in rabbits, indirect haemagglutination tests proved that they form a distinct group and there is no cross-reaction between them and the type strains of A. pleuropneumoniae. All five strains harboured the toxin-associated genes for the production (apxIA) and secretion (apxIB) of ApxI, the gene for the expression of ApxII and the largest-size (2800 bp) apxIV gene. The carbon source utilisation pattern and the sequence analysis of the 16S rRNA gene confirmed the species identification of the suggested type strain, A. pleuropneumoniae A-85/14. A new serovar of A. pleuropneumoniae - serovar 16 - is proposed with A. pleuropneumoniae A-85/14 as reference strain.
Keywords: Actinobacillus pleuropneumoniae; new serovar; serovar 16; untypable strain.