Actinobacillus pleuropneumoniae is the etiological agent of porcine pleuropneumonia, which causes serious economic losses in the pig-rearing industry. Serotyping is widely performed in veterinary diagnostic laboratories since virulence differs between serovars and vaccines for A. pleuropneumoniae are serovar specific. To date, 15 serovars have been recognized mainly based on the antigenic diversity of CPS in the organisms, but also by lipopolysaccharide (LPS) O-polysaccharide (O-PS). However, O-PS antigens are shared by multiple CPS serovars. Consequently, a serotyping scheme with the designations such as K12:O12, K3:O3, K8:O3 and K15:O3 (K and O are CPS and O-PS serovar, respectively) has been proposed. The combination of K and O antigens, which are expressed in A. pleuropneumoniae, are usually inherent within each serovar. However, we describe here the first isolation and characterization of a new serovar K12:O3 strain, even though typical CPS-serovar 12 strains are K12:O12. The emergence of an atypical A. pleuropneumoniae serovar K12:O3 strain expressing a rare combination of CPS and O-PS antigens would hamper precise serodiagnosis by the use of either CPS- or LPS O-PS-based serodiagnostic methodology alone. Since two other serovar K12:O3-like strains have been isolated in two other prefectures, prevalence of the new serovar A. pleuropneumoniae should be monitored.
(Bacterial and Parasitic Disease Research Division)
Ito H, et al (2015) J. Vet. Diagn. Invest.27:102-106