Serotyping of Actinobacillus pleuropneumoniae based on whole genome sequencing: validation of a bioinformatic tool

Serovar detector is a new bioinformatic tool for determining the serovar of Actinobacillus pleuropneumoniae using whole genome sequencing. The composition of cps genes of isolates is compared to those of the serovar reference strains, and the outcome is determined both by the number of common genes and the similarities between the homologous genes. The validation of the bioinformatic tool utilized a broad collection of 732 isolates, including representatives from all described serovars. The isolates included had been characterized by conventional serotyping, PCR tests or different bioinformatic tools. The collection also includes isolates that have been difficult to allocate to a serovar using serology to test the performance of the Serovar detector when potential new varieties or combinations of cps genes are present. Out of the 732 isolates included in the investigation, only 36 isolates (4.9%) could not be allocated to the 19 recognized serovars. The validation showed that the Serovar detector is a robust method for determining the serovar of an isolate and a valuable tool for further characterization of the genetic heterogeneity both within serovars and within the A. pleuropneumoniae species.