Actinobacillus
pleuropneumoniae is
the causative agent of porcine pleuropneumonia and contributes to substantial
economic losses in the swine industry worldwide. There are currently a total of 15 serovars recognised. In recent years we have observed submissions
from farms previously free of pleuropneumonia.
We have also had an increase in submissions of Actinobacillus-like isolates.
In this study the prevalence of A.
pleuropneumoniae serovars over 11 years and the occurrence of related
species were investigated. The study
also examined the hypothesis that serovar 5 isolates had limited genetic
diversity. The 336 isolates of App sumitted from February 2002 until
April 2013 were serotyping via gel diffusion, indirect haemagglutination and
multiplex PCR. Genotyping of the serovar
5 isolates was performed with the enterobacterial repetitive intergenic consensus
(ERIC) PCR. Partial sequencing of the
16S rDNA gene and blast analysis was done to determine the species of the Actinobacillus-like isolates, with the
gene being first amplified with primers 27F, 519R, 530F and 1525R. There appears to have been a shift in
serovars in 2012 with serovar 12 submissions from outbreaks being more
prominent than in previous years. When
determining the genotype of serovar 5 isolates in the period from 2002 to 2013,
all 27 isolates, originating from 11 farms from three Australian States,
displayed the same genetic fingerprint.
This suggests that the isolates are a single clone and of one origin.
Twenty-eight Actinobacillus-like
isolates were submitted in the period of October 2011 until November 2012. Thirteen of these isolates had the same ERIC
profile, yet four of them were identified (minimum of 96% identity) as A. indolicus, six as A. porcitonsillarum and three as A. porcitonsillarum/minor complex. Further
investigations into the Actinobacillus-like
isolates that have emerged in the last year are necessary to define the species
of these isolates.