Typhoidal Salmonellae: Use of Multi-Locus Sequence Typing to Determine Population Structure

Area of Science:

• Microbiology
• Epidemiology
• Molecular Biology

Background:

• Enteric fever, caused by Salmonella Typhi and Paratyphi A, is a significant global health concern.
• Antimicrobial resistance in these pathogens complicates treatment and facilitates spread through travel.
• Understanding pathogen diversity is crucial for effective disease control and prevention strategies.

Purpose of the Study:

• To determine the population structure and prevalence of Multilocus Sequence Typing (MLST) sequence types of Salmonella Typhi and Paratyphi A in India.
• To provide molecular data for informing enteric fever epidemiology and control.

Main Methods:

• Multilocus Sequence Typing (MLST) was performed on 251 Salmonella Typhi and 18 Salmonella Paratyphi A isolates.
• Strains were collected from enteric fever patients across seven Indian centers between 2010 and 2013.

Main Results:

• Five sequence types (STs) were identified: ST1, ST2, and ST3 for S. Typhi, and ST85 and ST129 for S. Paratyphi A.
• S. Typhi isolates showed a monophyletic lineage, with ST1 being the most prevalent, followed by ST2, consistent with global data.
• A rare S. Typhi ST3 was identified for the first time in the Indian subcontinent; S. Paratyphi A predominantly comprised ST129.

Conclusions:

• The study identified key MLST sequence types for Salmonella Typhi and Paratyphi A circulating in India.
• Prevalence data for these sequence types supports understanding global distribution and aids in developing targeted disease control measures.
• No association was found between antimicrobial susceptibility and the identified sequence types.