Genome characteristics of Bordetella pertussis isolates from Tunisia

The recent increase in pertussis cases observed in some countries may have several causes, including the evolution of Bordetella pertussis populations towards escape of vaccine-induced immunity. Most genomic studies of B. pertussis isolates performed so far are from countries that use acellular vaccines. The objective was to analyse genomic sequences of isolates collected during the 2014 whooping cough epidemic in Tunisia, a country where whole-cell vaccines are used. Ten Tunisian isolates and four vaccine strains were sequenced and compared to 169 isolates from countries where acellular vaccines are used. Phylogenetic analysis showed that Tunisian isolates are diverse, demonstrating a multi-strain 2014 epidemic peak, and are intermixed with those circulating in other world regions, showing inter-country transmission. Consistently, Tunisian isolates have antigen variant composition observed in other world regions. No pertactin-deficient strain was observed. The Tunisian B. pertussis population appears to be largely connected with populations from other countries.