Genetic diversity and toxin gene distribution among serovars of Actinobacillus pleuropneumoniae from Australian pigs

Abstract

Objective To explore the diversity among isolates of the Actinobacillus pleuropneumoniae serovars most common in Australia (serovars 1, 5, 7 and 15) and to examine the Apx toxin profiles in selected representative isolates.Design A total of 250 isolates selected from different farms were examined for their genotypic profiles and a subset of 122 isolates for their toxin profiles.Methods The isolates of serovars 1, 5, 7 and 15 selected for this study came from different farms and different Australian states and were submitted for serotyping to the reference laboratory. The overall diversity of the strains was explored with the enterobacterial repetitive intergenic consensus (ERIC) PCR and the presence of the toxin genes was investigated with a toxin PCR assay.Results Some degree of variation was observed in the ERIC-PCR pattern within all four serovars, ranging from 38% to 61% genetic diversity. When looking at the toxin gene profile and, therefore, the predicted ability to produce the expected toxin pattern, one isolate each of serovars 1 (n = 20) and 7 (n = 47) and 17 isolates of serovar 15 (n = 40) showed variation to the expected gene profile. ConclusionThe variations in toxin gene patterns, as detected by PCR, found in this study could be related to significant changes in the gene sequence or total absence of the gene. Variation in toxin gene sequences has been observed in other countries. This variation in the toxin profile could also explain possible variation in pathogenicity observed in the field.Keywords Actinobacillus pleuropneumoniae; Apx toxin; apx genes; Australia; pigs Abbreviations ERIC, enterobacterial repetitive intergenic consensus; UV, ultraviolet A ctinobacillus pleuropneumoniae is the causative agent of porcine pleuropneumonia and the virulence of the organism is associated with the exotoxins ApxI, ApxII and ApxIII.

Diverse strains of Actinobacillus lignieresii isolated from clinically affected cattle in a geographically restricted area

“…In the current study, we used ERIC PCR, which has been used for studies of the diversity of other members of the family Pasteurellaceae, including Haemophilus parasuis and A. pleuropneumoniae. 13,18 Four different patterns were distinguishable among the nine isolates we examined. As these nine isolates came from a single host species and only two farms, a greater diversity might be expected if more cattle from more farms were examined.…”

“…In the current study, we used ERIC PCR, which has been used for studies of the diversity of other members of the family Pasteurellaceae , including Haemophilus parasuis and A. pleuropneumoniae . Four different patterns were distinguishable among the nine isolates we examined.…”

In this issue – October 2018: Mechanisms and treatment of tumour angiogenesis is · Coagulation times depend on methods used · Experimental studies on footrot control · Pasteurella multocida in pigs and poultry · Pomegranate poisoning in cattle · Outcome of foals with hypernatremia

“…I also need to make an apology to our pig veterinarians, if I inadvertently caused you some unintended worry in our January/February issue this year. We published a paper on Actinobacillus pleuropneumoniae in Australia pigs . Unfortunately, due to an editorial mishap, the pointer on the front cover said “Genetic diversity in porcine virus”.…”

“…We published a paper on Actinobacillus pleuropneumoniae in Australia pigs. 10 Unfortunately, due to an editorial mishap, the pointer on the front cover said "Genetic diversity in porcine virus". Many thanks to eagle-eyed readers who pointed out that we were not reporting on a newly discovered virus disease.…”

In this issue – January/February 2018

“…A genetic study in Australian pigs highlights the need for more research into the variability in virulence of serovars of Actinobacillus pleuropneumoniae. 3 This organism is responsible for porcine pleuropneumonia, and the virulence of each serovar is related to the combination of the haemolytic and cytotoxic exotoxins that they produce. Using ERIC-PCR, this genetic study found wide variation in the toxin patterns in Australian serovars.…”