High Prevalence of Macrolide-resistant ptxP3-prn150 Bordetella pertussis in Jiangsu Province, China, 2024

A significant surge in pertussis cases since early 2023 has raised serious public health concerns. To investigate the potential mechanisms contributing to this increased prevalence, we collected throat swab specimens from children exhibiting pertussis symptoms and conducted detailed molecular characterization. All Bordetella pertussis (B. pertussis) isolates underwent whole-genome sequencing using the Illumina HiSeq platform (Illumina, San Diego, CA). Genome annotation was conducted with Prokka (https://github.com/tseemann/prokka/). Allele typing of key antigens and 23S rRNA mutations was determined using the Bordetella BIGSdb database. A phylogenetic tree was constructed using the maximum likelihood method based on core genome single-nucleotide polymorphisms. A total of 118 nasopharyngeal swab specimens were collected from patients diagnosed with B. pertussis infection. Of these, 48 isolates were successfully cultured and subjected to whole-genome sequencing. Genotyping revealed that 47 of these isolates shared the allelic profile ptxA1-ptxB1-ptxC4-ptxD1-ptxE4-ptxP3-fim2-1/fim3-1. All isolates exhibited bapC1 and brkA1/tcfA2//vag8/fhaB2 profiles, and belonged to the prn150 allele. Notably, approximately half of the isolates possessed an intact prn gene due to the insertion of IS481. A high prevalence of macrolide resistance was observed, with 97.5% of isolates carrying the A2047G mutation in the 23S rRNA gene. Phylogenetic analysis demonstrated significant genetic diversity between the circulating B. pertussis strains in Jiangsu Province and vaccine strains. The increasing prevalence of macrolide-resistant B. pertussis strains exhibiting ptxP3-prn150 genotype poses a significant challenge to both disease control and treatment. The high virulence associated with these strains, coupled with antibiotic resistance, underscores the urgent need for the development of novel vaccine strategies to effectively combat this emerging threat.