ORIGINAL ARTICLE Strain variation and antigenic divergence among Bordetella pertussis circulating strains isolated from patients in Iran Fatemah Sadeghpour Heravi 1 & Vajihe Sadat Nikbin 1 & Masomeh Nakhost Lotfi 1 & Pouran Badiri 1 & Nazanin Jannesar Ahmadi 1 & Seyed Mohsen Zahraei 1 & Fereshteh Shahcheraghi 1 Received: 2 May 2018 /Accepted: 4 July 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Despite global efforts and widespread vaccination to control whooping cough (pertussis) caused by B. pertussis, the re- emergence of pertussis still is being reported all over the world. Antigenic divergence in B. pertussis virulence factors is one of the reasons of pertussis resurgence, resulting in dissimilarity of local and vaccine strains. In this study, clonal spread and variation of B. pertussis virulence factor in isolated strains from Iranian patients have been analyzed. A total of 100 B. pertussis isolates were obtained from Pertussis Reference Laboratory of Pasteur Institute of Iran. Real-time PCR were performed to confirm the B. pertussis strains. The genomic patterns of B. pertussis strains were analyzed by pulsed-field gel electrophoresis (PFGE). Predominant alleles of local strains were ptxP3, ptxA1, prn2, fim 2-1, fim3-2, and cya2. PFGE results showed 25 patterns clustered into 18 PFGE groups. A few similarities between the circulating isolates, vaccine, and standard strains were obtained. Significantly, 48% of the isolates showed dominant pattern with different allelic profiles from vaccine strains. According to the genomic profiles, the clonal spread was observed among the circulating strains. Predominant virulence factor profile was also comparable with other countries. It may be suggested that strain variation between vaccine and local strains may have an effect on pertussis resurgence in Iran like other parts of the world. Keywords Bordetella pertussis . Pulsed-field gel electrophoresis (PFGE) . Resurgence . Virulence factors . Vaccine Introduction The problem of whooping cough (pertussis) as a vaccine pre- ventable disease is still unresolved worldwide. The spread of Bordetella pertussis as the agent of this respiratory illness has been observed globally [1]. Despite high coverage of vaccination around the world, pertussis incidence has been reported from many developed and developing countries like the USA, Canada, Australia, and countries in Southeast Asia and Africa [2–4]. Also, recent outbreaks have been observed in California between 2010 and 2014 [5, 6] and in the UK in 2012 [7]. Availability of vaccines aimed at controlling and eradicat- ing the disease have proved unsuccessful and cases continue to be recorded among patients of all ages [8]. There are a number of reasons behind this fact, such as waning vaccine-induced immunity, increased awareness, im- proved diagnostic methods, decrease in vaccine quality and expansion of novel strains which are antigenically different from vaccine strains [9]. Resurgence of pertussis via pathogen adaption has been published in different countries such as the Fatemah Sadeghpour Heravi and Vajihe Sadat Nikbin have equally collaborated and should be considered co-first authors. * Fereshteh Shahcheraghi shahcheraghifereshteh@yahoo.com Fatemah Sadeghpour Heravi f.sadeghpour1989@gmail.com Vajihe Sadat Nikbin vsnikbin@yahoo.com Masomeh Nakhost Lotfi naderehlotfi116@gmail.com Pouran Badiri badiripouran@gmail.com Nazanin Jannesar Ahmadi just_microbiology@yahoo.com 1 Pertussis Reference Laboratory‚ Department of Bacteriology, Pasteur Institute of Iran, Tehran, Iran European Journal of Clinical Microbiology & Infectious Diseases https://doi.org/10.1007/s10096-018-3323-6