Identification of the Actinobacillus pleuropneumoniae serotype using PCR based-apx genes

Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is an important swine respiratory disease pathogen, which has at least 15 serotypes. There are several techniques for the serotyping of A. pleuropneumoniae, however, these techniques are time consuming. In this study, the polymerase chain reaction (PCR) technique was developed for serotyping A. pleuropneumoniae using a set of specific primer designated for the apxI, apxII, apxIII and apxIVA genes. By this PCR typing system, 10 out of the 13 reference strains of A. pleuropneumoniae were differentiated. However, it was not possible to distinguish serotype 2 from 8, serotype 5a from 5b and serotype 9 from 11. Each serotype of A. pleuropneumoniae showed its own products patterns. The PCR typing system was further applied for typing the field isolates of A. pleuropneumoniae and compared to that using the gel immunodiffusion (GID) technique. The results from both PCR and GID techniques were in accordance. Thus, the PCR typing system may provide a rapid and useful tool for typing the serotypes of A. pleuropneumoniae.