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Simple Summary: Actinobacillus (A.) pleuropneumoniae is a major agent of the porcine respiratory diseases complex (PRDC), together with several bacterium and virus species. A. pleuropneumoniae strains are diverse regarding virulence and antigen structure; they have different virulence variants, and the strains can be assigned into 19 serovars. Serovar 16 was described in Hungary for the first time, and it is relatively frequent in pig herds. The aim of the present work was examination of the virulence of the A. pleuropneumoniae A-85/14 strain, the type strain of serovar 16, by infecting piglets. The results prove that the A. pleuropneumoniae A-85/14 strain is a virulent one. Different virulence variants of A. pleuropneumoniae are involved in the etiology of porcine pleuropneumonia. The purpose of the present trial was examination of the virulence of the Actinobacillus pleuropneumoniae A-85/14 strain, the type strain of serovar 16, in an animal challenge experiment. Thirty 12-week-old piglets seronegative for A. pleuropneumoniae were allocated into three trial groups each of 10 animals, and they were infected intranasally with 106, 107, or 108 colony forming units (cfu) of the strain, respectively. Clinical signs were recorded twice a day, and the animals were euthanized 6 days after the infection. Typical clinical signs and postmortem lesions of porcine pleuropneumonia were seen in the animals of each trial group; however, they were generally mild, and no significant differences could be seen between the three groups. Even 106 colony forming units of A. pleuropneumoniae A-85/14 strain could induce clinical signs and lesions. Based on these results, the type strain of serovar 16 of A. pleuropneumoniae must be regarded as a typical pathogenic strain of the species. [ABSTRACT FROM AUTHOR]

Different virulence variants of A. pleuropneumoniae are involved in the etiology of porcine pleuropneumonia. The purpose of the present trial was examination of the virulence of the Actinobacillus pleuropneumoniae A-85/14 strain, the type strain of serovar 16, in an animal challenge experiment. Thirty 12-week-old piglets seronegative for A. pleuropneumoniae were allocated into three trial groups each of 10 animals, and they were infected intranasally with 106, 107, or 108 colony forming units (cfu) of the strain, respectively. Clinical signs were recorded twice a day, and the animals were euthanized 6 days after the infection. Typical clinical signs and postmortem lesions of porcine pleuropneumonia were seen in the animals of each trial group; however, they were generally mild, and no significant differences could be seen between the three groups. Even 106 colony forming units of A. pleuropneumoniae A-85/14 strain could induce clinical signs and lesions. Based on these results, the type strain of serovar 16 of A. pleuropneumoniae must be regarded as a typical pathogenic strain of the species.

Actinobacillus pleuropneumoniae causes pleuropneumonia, an economically significant lung disease of pigs. Recently, isolates of A. pleuropneumoniae that were serologically distinct from the previously characterized 15 serovars were described, and a proposal was put forward that they comprised a new serovar, serovar 16. Here we used whole-genome sequencing of the proposed serovar 16 reference strain A-85/14 to confirm the presence of a unique capsular polysaccharide biosynthetic locus. For molecular diagnostics, primers were designed from the capsule locus of strain A-85/14, and a PCR was formulated that differentiated serovar 16 isolates from all 15 known serovars and other common respiratory pathogenic/commensal bacteria of pigs. Analysis of the capsule locus of strain A-85/14 combined with the previous serological data show the existence of a sixteenth serovar-designated serovar 16-of A. pleuropneumoniae ., (Copyright © 2017 Bossé et al.)

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.