fa Original article Original article <div style="text-align: justify;"><strong>Introduction:</strong> 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 <em>Bordetella pertussis </em>has been occurred over the years. It is suggested that the predominant genomic profile of <em>B. pertussis</em> has an enough capacity to spread among the population. The aim of this study was to characterize a predominant <em>B. pertussis</em> strain isolated from Iranian patients during 2008-2015 period. <strong>Methods:</strong> Based on the epidemiologic results of <em>B. pertussis</em> 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. <strong>R</strong><strong>esults: </strong>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 &times; 10¹⁰ and 4 &times; 10⁶ colony forming units, respectively. <strong>Conclusion: </strong>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.</div> Bordetella pertussis, wP vaccine, Circulating strain, Growth curve, LD50. 52 56 http://vacres.pasteur.ac.ir/browse.php?a_code=A-10-1-63&slc_lang=fa&sid=1 VS Nikbin vsnikbin@yahoo.com 0000-0002-6540-1003 No Pertussis Reference Laboratory, Bacteriology Department, Pasteur Institute of Iran, Tehran, Iran. M Keramati keramati.malihe@gmail.com 0000-0002-7196-8751 No Nano-Biotechnology Department, Pasteur Institute of Iran, Tehran, Iran. M Noofeli noofeli1234@yahoo.com 0000-0003-4991-4631 No Razi Vaccines and Serum Research Institute, Agricultural Research , Education and Extension Organization (AREEO), Karaj, Iran. N Bolourchi neginbolourchi@gmail.com 0000-0001-9893-6656 No Pertussis Reference Laboratory, Bacteriology Department, Pasteur Institute of Iran, Tehran, Iran. MS Shams Nosrati mohammadshams169@yahoo.com 0000-0002-5762-0601 No Pertussis Reference Laboratory, Bacteriology Department, Pasteur Institute of Iran, Tehran, Iran. F Shahcheraghi shahcheraghifereshteh@yahoo.com 0000-0001-5840-5375 Yes Pertussis Reference Laboratory, Bacteriology Department, Pasteur Institute of Iran, Tehran, Iran.