Bordetella avium hemagglutination and motility mutants: isolation, characterization, and pathogenicity

Transposon mutagenesis was used to produce Bordetella avium mutants, which were screened for the lack of potential virulence factors, including a hemagglutinin, flagella, pili, and toxins. A mini-Tn10 transposon containing a kanamycin-resistance gene was introduced into the chromosomal DNA of the virulent 002/S isolate by electroporation. A hemagglutination-negative (HA-) mutant and a motility-negative mutant were obtained. Southern blot analysis showed that only the motility-negative mutant contained the transposon, whereas the HA- mutant was a spontaneous kanamycin-resistant mutant. Both mutants were stable in vitro and in vivo. Following inoculation of 2-week-old poults, the HA- mutant was determined to be less virulent than the 002/S parent, whereas the motility-negative mutant was similar in virulence to the 002/S parent. These results indicate that the hemagglutinin of B. avium is a virulence factor, but motility does not appear to contribute to virulence.