Abstract:
Objective To analyze the etiological and evolutionary characteristics of the pathogen of a pertussis outbreak in a kindergarten in Shenzhen, Guangdong province, in 2024.
Methods The positive samples of Bordetella pertussis nucleic acid were used for pathogen isolation, culture, and antimicrobial susceptibility testing. Whole-genome sequencing was used to analyze the molecular characteristics of the isolates. Molecular tracing and phylogenetic analysis were conducted based on the genomic data from 552 B. pertussis isolates nationwide and 203 strains of the ptxP3 lineage, the clone of macrolide-resistant MT28 genotype (MR-MT28).
Results Three B. pertussis strains were isolated, which belonged to macrolide-resistant MR-MT28 clone (ptxP3 lineage) carrying A2047G mutation. The strains exhibited high homogeneity (single nucleotide polymorphism (SNP) ≤1) and close genetic relationship with Shanghai isolates from 2021 to 2024 (SNP = 4, n = 8), the cases all had no travel histories. The proportion of ptxP3 lineage in the strains isolated in China increased greatly from 9.93% in 2015 to 82.76% during 2020−2024. Compared with vaccine strain Tohama I/CS, the MR-MT28 clone strains showed antigenic drift at four key loci, ptxP3, ptxA1, ptxC4, and prn150.
Conclusion The outbreak was confirmed to be caused by the local transmission of MR-MT28 clone strain of B. pertussis in Shenzhen, suggesting the spread risk for in other parts of China. It is suggested to strengthen the surveillance for pertussis pathogen based on whole genome sequencing, dynamically monitor and evaluate the potential impact of antigen drift on pathgogen drug resistance and vaccine protection immune escape.
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