Sharp rise in high-virulence Bordetella pertussis with macrolides resistance in Northern China

To elucidate the evolution of antigen genotype and antimicrobial resistance distribution of <i>Bordetella pertussis</i> (<i>B. pertussis</i>) from 2019 to 2023 in northern China. Polymerase chain reaction (PCR) amplification and sequencing were utilized to identify the seven antigen genotypes (<i>ptxA, ptxC, ptxP, prn, fim2, fim3, tcfA</i>). E-test and Kirby-Bauer (K-B) disc diffusion were employed to determine the minimum inhibitory concentration (MIC) and zone of inhibition for <i>B. pertussis</i> against antimicrobial agents. Subsequently, 50 isolates were chosen for multi-locus variable-number tandem-repeat analysis (MLVA) typing and whole-genome sequencing. A total of 442 <i>B. pertussis</i> isolates were determined. The strains with high virulence harbouring <i>ptxP3</i> allele surged from 13.5% (21/155) in 2019–2021 to 93.0% (267/287) in 2022–2023. Concurrently, the erythromycin resistance <i>B. pertussis</i> (ERBP) in <i>ptxP3</i> isolates markedly rose from 42.9% (9/21) in 2019–2021 to 100% (267/267) in 2022–2023. The majority of <i>ptxP3</i> isolates (76.0%,219/288) exhibited the <i>ptxA1/ptxC1/prn2/fim2-1/fim3A/tcfA-2</i> genotype. Among the 442 confirmed patients, the children aged 3–14 years escalated rapidly from 13.5% in 2019 to 45.6% in 2023. The MT28 strains were responsible for 66.0% (33/50) of the tested ones, in which ERBP was prevalent at 87.9% (29/33). All the present sequenced <i>ptxP3</i>-ERBP strains (31/31) were clustered into the sub-lineage IVd. These results suggested the clonal spread of the <i>ptxP3</i>-ERBP lineage of <i>B. pertussis</i> with high virulence and macrolides resistance could be an important cause of the recent pertussis resurgence in China. Furthermore, the increased cases among pre-school and school-aged children underscore the importance of booster vaccination in this population.