Circulation of Third-Generation Cephalosporin Resistant Salmonella Typhi in Mumbai, India

Area of Science:

• Microbiology
• Infectious Diseases
• Genetics

Background:

• Salmonella Typhi causes typhoid fever, a significant global health concern.
• Antimicrobial resistance in Salmonella Typhi, particularly to third-generation cephalosporins and fluoroquinolones, poses a therapeutic challenge.
• The emergence and spread of resistant strains necessitate ongoing surveillance.

Purpose of the Study:

• To investigate the persistent circulation of third-generation cephalosporin resistant Salmonella Typhi in Mumbai.
• To identify the genetic mechanisms underlying this resistance.
• To understand the role of mobile genetic elements in the dissemination of resistance.

Main Methods:

• Genomic analysis of resistant Salmonella Typhi isolates.
• Plasmid profiling and characterization.
• Identification of antimicrobial resistance genes and their genetic context.

Main Results:

• Confirmation of persistent circulation of third-generation cephalosporin resistant Salmonella Typhi in Mumbai.
• Identification of an IncX3 plasmid carrying the blaSHV-12 (extended-spectrum beta-lactamase) and qnrB7 (fluoroquinolone resistance) genes.
• The resistance genes were found within a triple mutant genetic context also associated with fluoroquinolone resistance.

Conclusions:

• The IncX3 plasmid plays a crucial role in the maintenance and spread of multidrug resistance in Salmonella Typhi in Mumbai.
• The co-acquisition of resistance genes on mobile elements contributes to the evolution of highly resistant strains.
• Continued monitoring of antimicrobial resistance patterns and molecular mechanisms is essential for effective typhoid fever management.