Emerging of ptxP3 lineage in Bordetella pertussis strains circulating in a population in northeastern Mexico

Abstract

We determined the molecular epidemiology of Bordetella pertussis isolates to evaluate its potential impact on pertussis reemergence in a population of Mexico. Symptomatic and asymptomatic cases were included. Pertussis infection was confirmed by culture and real-time polymerase chain reaction (PCR). Selected B. pertussis isolates were further analysed; i.e. clonality was analysed by pulsed-field gel electrophoresis (PFGE) and ptxP-ptxA, prn, fim2 and fim3 typing was performed by PCR and sequencing. Out of 11 864 analysed samples, 687 (5.8%) were positive for pertussis, with 244 (36%) confirmed by both culture and PCR whereas 115 (17%) were positive only by culture and 328 (48%) were positive only by PCR. One predominant clone (clone A, n = 62/113; 55%) and three major subtypes (A1, A2 and A3) were identified by PFGE. All 113 selected isolates had the allelic combination ptxP3-ptxA1. The predominant clone A and the three major subtypes (A1, A2 and A3) corresponded to the emerging genotypes ptxP3-ptxA1-prn2-fim2-1-fim3-2 and ptxP3-ptxA1-prn2-fim2-1-fim3-1. In conclusion, the presence of an endemic clone and three predominant subtypes belonging to the genotypes ptxP3-ptxA1-prn2-fim2-1-fim3-2 and ptxP3-ptxA1-prn2-fim2-1-fim3-1 were detected. This finding supports the global spread/expansion reported for these outbreaks associated genotypes.

Keywords: Bordetella pertussis; Mexico; genotyping; ptxP3; pulsed-field gel electrophoresis.

Fig. 1.

Pulsed-field gel electrophoresis analysis of 113 B. pertussis isolates collected from 2007 to 2014. ¹number and percent of isolates corresponding to each genotype. ²Similarity coefficient generated using SPSS 20.0 software.

Fig. 2.

Temporal relation of the hypervirulent clone (A) and subtypes (A1, A2 and A3) over the years. Bars represent the incidence of reported cases of pertussis (per 100 000 hab) by years, in Nuevo Leon, Mexico, from 2007 to 2014.