Molecular characterization of the HMTp210 gene of Avibacterium paragallinarum and the proposition of a new genotyping method as alternative for classical serotyping.

is the etiological agent of infectious coryza (IC) in chickens and characterized by acute respiratory distress and severe drop in egg production. Vaccination is important in the control of IC outbreaks and the efficacy of vaccination is dependent on serovars included in the vaccine. Classical serotyping of is laborious and hampered by the poor availability of antigens and antisera. The hemagglutinin (HA), important in classical serotyping is encoded by the gene. gene analysis has shown to have potential as alternative for classical serotyping. The aim of the present study was to further investigate the potential of sequence analyses of nucleotides 1-∼1200 of region one of the gene, the hypervariable region and the concatenated sequences of both gene fragments. For this analysis 123 gene sequences (field isolates, serovar reference strains and vaccine strains) were included. Evaluation of serovar references and vaccine strains revealed a need for critical evaluation, especially within Page serovar B and C. Phylogenetic analysis of region 1 resulted in a separation of Page serovar A, B and C strains. Analysis of the HVR alone was not sufficient to discriminate all nine different Kume serovar references. The concatenated sequences of region 1 and HVR resulted in fourteen clusters with a high correlation with Page serovar and with the nine currently known Kume serovars and is therefore proposed as a novel genotyping method that could be used as an alternative for classical serotyping of .