RTX toxin genotypes and phenotypes in Actinobacillus pleuropneumoniae field strains

Abstract

Actinobacillus pleuropneumoniae serotype reference strains and 204 A. pleuropneumoniae field strains representing all 12 serotypes and both biovars 1 and 2, obtained from laboratories from various countries worldwide, were analyzed for the presence of the toxin genes apxIC, apxIA, apxIB, apxID, apxIIC, apxIIA, apxIIIC, apxIIIA, apxIIIB, and apxIIID by DNA-DNA hybridization with specific gene probes. Expression of the toxins ApxI, ApxII, and ApxIII was assessed by immunoblot analysis with monoclonal antibodies. The results show that the patterns of apx genes and those of the expressed Apx toxins in biovar 1 field strains are the same as those of the genes and toxins of corresponding serotype reference strain. We found only three strains which had certain apx genes missing compared with the genes in their serotype reference strains. Analysis of the expression of the three toxins showed that nearly all strains expressed their apx genes and produced the same Apx toxins as their serotype reference strain. We found only one strain that did not produce ApxI, although it contained the apxICABD genes, and one strain which did not express ApxII but which contained apxIICA. Several field strains which initially showed that their serotype did not correspond to the apx gene profile of the reference strain and which had an unexpected virulence for the given serotype revealed that their initial serotyping was erroneous. We show that the apx gene profiles are inherent to a given serotype. The method cannot differentiate between all 12 serotypes. However, it allowed us to distinguish five groups of toxin gene patterns which showed pathological, toxicological, and epidemiological significance. None of the biovar 2 strains contained apxIII genes. The apxI and apxII genes in the biovar 2 strains, however, were the same as those found in the serotype reference strains of biovar 1.

Genomic differences betweenActinobacillus pleuropneumoniaeserotypes 1 and 3 and the diversity distribution among 15 serotypes

“…Previous studies suggested that these cross-reactions can be primarily attributed to shared species-specific antigens such as lipopolysaccharide or membrane proteins (Perry et al, 1990). In our study, the distribution of the apxI and apxIII operon was in agreement with that presented in the previous report (Beck et al, 1994), and these operons have been shown to play the roles of immune-protective antigens (Du et al, 2008). However, this is the first report on the distribution of other differential genes (the encoded proteins are listed in Tables 3 and 4).…”

Antibodies against 12 Serotypes of Actinobacillus pleuropneumoniae in Finnish Slaughter Sows

“…Serotype 3 has been known to contaminate pig farms in Finland, but it has not caused acute epidemics. This is typical for serotype 3 strains, which have previously been shown to be less pathogenic in certain areas (NIELSEN, 1982;NI(:oL~:T, 1992;Mot R et al, 1992;BECK et al, 1994). Variation in the virulence of serotype 2 strains has also been reported.…”

“…Pigs that survive A. pkumpneumoniae infection often become subclinical carriers of the bacterium (NIELSEN, 1982). A. pkumpneumoniae can be differentiated into 12 serotypes and into two biovars (biovar 1, NAD dependent, biovar 2, NAD independent) (NIFLSEN, 1986;BECK et al, 1994). Serology and serotyping are the most important tools in epidemiology and sanitation programmes to control swine pleuropneumonia (NICOLET, 1992;BECK et al, 1994).…”

“…A. pkumpneumoniae can be differentiated into 12 serotypes and into two biovars (biovar 1, NAD dependent, biovar 2, NAD independent) (NIFLSEN, 1986;BECK et al, 1994). Serology and serotyping are the most important tools in epidemiology and sanitation programmes to control swine pleuropneumonia (NICOLET, 1992;BECK et al, 1994). An extensive knowledge of the different serotypes which exist in a particular region is required in order to be able to control A. pleumpneumoniae infections (GUNNARSSON, 1980;M~A L and BOURDON, 1991;ZIMMERMANN and STAEGER, 1993).…”

Update onActinobacillus pleuropneumoniae-knowledge, gaps and challenges

“…Normally, serovars 1-12 and 15-16 are biovar 1, and serovars 13 and 14 are biovar 2. However, some biovar 2 isolates belonging to serovars other than 13 and 14(Beck et al, 1994;Dom & Haesebrouck, 1992;Maldonado, Valls, Mart ınez, & Riera, 2009), as well as a biovar 1 serovar 13 isolate(Perry et al, 2012), have been identified. Additionally, some untypable isolates have been reported(Ito, Ogawa, Fukamizu, Morinaga, & Kusumoto, 2016;Kokotovic & Angen, 2007).…”