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Domination of an emerging erythromycin-resistant ptxP3 Bordetella pertussis clone in Shanghai, China
Jiehao Cai1, Mingliang Chen2, Qiyi Liu1
1Department of Infectious Diseases, Children's Hospital of Fudan University, Shanghai, PR China.
Abstract:
The number of cases of pertussis has been increasing since 2014 in China, with high prevalence of macrolide resistance in ptxP1 isolates and low prevalence in ptxP3 isolates. This study aimed to investigate the dynamic changes in the B. pertussis population from paediatric patients and household contacts in Shanghai between 2018 and 2022. Clinical data of laboratory-confirmed cases of pertussis were analysed, while isolates recovered from hospitalized children and household contacts were characterized by antimicrobial susceptibility testing, whole-genome sequencing, vaccine antigen gene typing and phylogenetical analysis. Among 640 laboratory-confirmed cases, 340 (53.1%) were fully vaccinated with DTaP and 114 (17.8%) were hospitalized for treatment. The frequency of erythromycin resistance in the 103 B. pertussis isolates from inpatients (n=73) and household contacts (n=30) was 78.6% (81/103), increasing from 65% (13/20) in 2018 to 100% (26/26) in 2022. The proportion of ptxP3 isolates increased from 35% (7/20) in 2018 to 100% (26/26) in 2022. Based on genomic analysis, a novel ptxP3 clone (MT28-Shanghai) belonging to sublineage IVd was discovered and dominated in 2021-2022, which was characterized with ptxP3, erythromycin resistance and prn150. Twelve (11.7%) predicted pertactin-deficient isolates were found; of these, nine were ptxP3 isolates and three were ptxP1 isolates. A complete shift from ptxP1 to ptxP3 in Shanghai, China, which may have been accelerated by the domination of a novel erythromycin-resistant MT28 clone, challenges the pertussis vaccines used at present in China.
Insights
Pertussis (whooping cough) cases are rising in China. A new, drug-resistant pertussis strain (ptxP3) has emerged, potentially impacting current vaccine effectiveness.
Area of Science:
- Microbiology
- Epidemiology
- Genomics
Background:
- Pertussis (whooping cough) incidence has increased in China since 2014.
- Macrolide resistance is prevalent in ptxP1 Bordetella pertussis strains, but less so in ptxP3 strains.
- Understanding B. pertussis population dynamics is crucial for public health interventions.
Purpose of the Study:
- To investigate dynamic changes in the B. pertussis population in Shanghai.
- To analyze B. pertussis isolates from pediatric patients and household contacts between 2018 and 2022.
- To characterize antimicrobial resistance and genetic profiles of circulating strains.
Main Methods:
- Analysis of clinical data from laboratory-confirmed pertussis cases.
- Antimicrobial susceptibility testing, whole-genome sequencing, and vaccine antigen gene typing of B. pertussis isolates.
- Phylogenetic analysis to determine strain relationships and evolution.
Main Results:
- Erythromycin resistance in B. pertussis isolates increased from 65% in 2018 to 100% in 2022.
- The proportion of ptxP3 isolates rose from 35% in 2018 to 100% in 2022.
- A novel erythromycin-resistant ptxP3 clone (MT28-Shanghai) dominated in 2021-2022, challenging existing pertussis vaccines.
Conclusions:
- A complete shift from ptxP1 to ptxP3 strains occurred in Shanghai.
- The emergence of a novel, drug-resistant MT28 clone accelerated this shift.
- Current pertussis vaccines in China may face challenges due to these evolving B. pertussis strains.
