Characterization of a predominant Bordetella pertussis strain isolated from Iranian patients

Pathogen adaptation is considered as one of the important reasons for the emergence of pertussis (whooping cough). Antigenic divergence between vaccine strains and clinical isolates of Bordetella pertussis has been occurred over the years. It is suggested that the predominant genomic profile of B. pertussis has an enough capacity to spread among the population. The aim of this study was to characterize a predominant B. pertussis strain isolated from Iranian patients during 2008-2015 period. Based on the epidemiologic results of B. pertussis circulating strains in Iran, a strain named BPIP91 with predominant genomic and virulence pattern was selected from Biobank of Pasteur Institute of Iran. The antibiotic susceptibility testing was done and the growth rate of this strain was analyzed. The lethal (LD50) and safety dose of infection of BPIP91 was also determined via mice intranasal infection. Our results showed that BPIP91 was susceptible to erythromycin, azithromycin, clarithromycin, chloramphenicol, trimethoprim-sulfamethoxazole and rifampin antibiotics. The growth rate of BPIP91 was almost two-fold lower than the vaccine strain. In addition, the LD50 and infectious dose of BPIP91 strain were about 2 × 1010 and 4 × 106 colony forming units, respectively. In this study we obtained the growth curve, LD50 and intranasal infectious dose of a circulating strain with predominant genomic pattern in Iran. However, further examinations including determination of immunogenicity of this native strain in animal model is needed in order to evaluate its use as a vaccine strain candidate.