Accumulation of avirulent Bordetella pertussis Bvg mutants in the course of experimental whooping cough in mice

The duration and dynamics of accumulation of insertional Bordetella pertussis Bvg − mutants were studied in the lungs of laboratory mice after intranasal and intravenous challenge by virulent bacteria of the causative agent of whooping cough. The ability of the virulent B. pertussis bacteria to remain for a long time in the body of mice was established. Using real-time PCR, a hundred genome equivalents of DNA of B. pertussis were detected in lungs of mice 2 months after infection regardless of type of challenge. Using the bacterial test bacteria were identified during only 4 weeks after challenge. Avirulent Bordetella pertussis Bvg − mutants were accumulated in the period of infection. The percentage of the avirulent bacteria in the B. pertussis population reached 50% in 7–9 weeks after challenge. The obtained results show that laboratory mice can be used to study the dynamics of accumulation of B. pertussis insertion mutants in vivo and confirm the hypothesis that there is accumulation of insertion avirulent Bordetella pertussis Bvg − mutants during development of pertussis infection in human.