Genomic perspective on the bacillus causing paratyphoid B fever.

Area of Science:

• Microbiology
• Genomics
• Epidemiology

Background:

• Paratyphoid B fever (PTB) is caused by an invasive lineage (phylogroup 1, PG1) of Salmonella enterica serotype Paratyphi B (SPB).
• Limited knowledge existed regarding the global population structure, geographic distribution, and evolution of SPB PG1.
• Understanding the pathogen's genomic landscape is crucial for effective disease control.

Purpose of the Study:

• To conduct a comprehensive whole-genome analysis of Salmonella Paratyphi B PG1 isolates.
• To elucidate the global population structure, geographic distribution, and evolutionary history of SPB PG1.
• To identify genomic markers associated with antimicrobial resistance.

Main Methods:

• Whole-genome sequencing of 568 historical and contemporary SPB PG1 isolates (1898–2021).
• Phylogenetic analysis to determine population structure and evolutionary relationships.
• Genomic analysis to identify mutations conferring antimicrobial resistance.

Main Results:

• SPB PG1 originated in the 13th century and diversified into 11 lineages and 38 genotypes with distinct phylogeographic patterns.
• The pathogen circulated in Europe until the 1970s, with subsequent reintroductions from South America, the Middle East, South Asia, and North Africa.
• Emergence of antimicrobial resistance, particularly quinolone resistance, was observed in various SPB PG1 genotypes due to mutations in gyrA and gyrB.

Conclusions:

• This study provides unprecedented genomic insights into the evolution and global dissemination of SPB PG1.
• Genomic tools developed can aid in identifying and tracking SPB PG1.
• Enhanced genomic surveillance is essential for monitoring and controlling Paratyphoid B fever globally.