MLST scheme for the porcine pathogen Actinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae (APL) is a bacterium that causes a world-wide economically important severe life threatening lung disease of pigs. Bacteria can be passed from pig to pig through the air or by direct contact. Not all APL bacteria are the same and methods to identify different types (typing schemes) have been developed. The most widely used one, called serotyping, recognises 10 different types of APL and is largely based on the different sugar coatings that APL may have. Knowing the serotype can help in making vaccines against APL but only gives us limited information as to the individual forms of APL that are around both locally and nationally. We are going to develop a typing scheme called MLST that uses the DNA sequence from specific genes of APL. MLST has the advantages that it can be used to track individual APL forms from all over the world. We intend to (1) apply MLST to UK and European isolates of APL (2) determine the serotype of APL isolated from pigs, to allow comparison of old and new schemes, and (3) determine which antibiotics, used to treat infected animals, are the best to use in the UK and Europe.

Actinobacillus pleuropneumoniae (APL) is a worldwide economically important swine pathogen responsible for either a devastating acute disease of lungs or chronic lung infection resulting in rapid death or decreased time to market weight respectively. APL is spread from pig to pig via direct contact or via respiratory droplets. The mainstay of strain classification for epidemiological purposes has been serotyping, based on surface polysaccharides, with 16 serotypes known. Particular serotypes appear to be associated with geographical locations and some are thought to be more virulent than others. For epidemiological studies there is a real need for an alternative more informative scheme. We propose to develop a multilocus typing sequence (MLST) scheme for APL and apply it to UK and European isolates. MLST schemes, widely used for other bacteria, are based on DNA sequencing 7 housekeeping genes. The advantages of an MLST scheme are that it allows clonal relationships between strains to be established and also comparison with strains from all over the world. Additional complementary studies will determine (1) the serotype and antibiotic resistance of those examples in the strain collections that area unknown and (2) determine the protein variability of potential recombinant vaccine antigens. The results will have implications for current treatment practices and vaccine design and be of interest to farmers, veterinarians, research workers and Vet Pharma.