Objective:To analysis the macrolide resistance, molecular characteristics and plused-field gel electrophoresis(PFGE) type of Bordetella pertussis ( Bp), explore the possible resistance mechanism and the relationship between PFGE types and macrolide resistance profiles. Methods:Erythromycin, azithromycin and clarithromycin susceptibility of clinical isolates during 2016 to 2018 was determined by E-test. PCR was used to detect the drug-resistant genes and mutation sites. PFGE were employed to do molecular typing for the strains.Results:Thirty-five strains were isolated, of which 27 strains were resistant to all three antibiotics, two strains were resistant to erythromycin and azithromycin, and six strains were sensitive to all three antibiotics. Partial macrolide resistant strains carried the methylase gene ermA (27.6%, 8/29) and ermB (31.0%, 9/29); A2047G site mutation was detected in macrolide-resistant strains, while no drug-resistant genes or mutation sites were found in sensitive strains. Resistant strains were classified into BPSR23 and BPFINR9 types, while sensitive strains were other profiles. Conclusions:The clinical isolated Bp were seriously resistant to erythromy and showed signs of resistance to other macrolides. The acquisition of methylase gene and mutation of A2047G site might be the main mechanism of resistance. The macrolide resistance might have has a certain correlation with PFGE profile.

Objective:To investigate the genetic diversity and molecular epidemiology of Bordetella pertussis in Shaanxi province, and analyze the possible reasons of resurgence in this region. Methods:We characterized clinical isolates collected during 2012-2017 using multilocus antigen sequence typing (MAST) and multilocus variable-number tandem repeat analysis (MLVA).Results:The circulating strains and vaccine strains were different in molecular characteristics. The majority (95%) of the isolates were typed as prn1/ ptxP1/ ptxA1/ fim3-1/ fim2-1. In addition, eight MLVA types (MTs) and eight PFGE profiles were identified, respectively. MT195, MT55 and MT104 were dominant and MT195 continually increased annually. Conclusions:The genetic characteristics of the current strains in Shaanxi province were different from those of the vaccine strain. The evolution through genetic variation might be one of the reasons for the recurrence of pertussis in this region.