Plasmid-mediated resistance to multiple antibiotics in Salmonella typhi

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Salmonella typhi causes typhoid fever, a significant public health concern.
• Antimicrobial resistance in S. typhi poses a growing challenge to effective treatment.
• Previous studies indicated emerging resistance patterns in S. typhi isolates.

Purpose of the Study:

• To assess the antimicrobial susceptibility of Salmonella typhi strains isolated in Lima, Peru.
• To identify effective antimicrobial agents against multidrug-resistant S. typhi.
• To characterize the resistance mechanisms and plasmid profiles of resistant strains.

Main Methods:

• Antimicrobial susceptibility testing using standard methods for 241 S. typhi isolates.
• Determination of minimal inhibitory concentrations (MICs) for 17 antimicrobial agents against resistant strains.
• Plasmid analysis and transferability experiments using Escherichia coli C1.

Main Results:

• 29.9% of S. typhi strains exhibited resistance to chloramphenicol and other antibiotics (ampicillin, sulfonamides, trimethoprim).
• Newer agents like Sch 25393, novel beta-lactams, new quinolones, and clavulanic acid-amoxicillin were effective against all tested resistant strains.
• Four distinct resistance patterns were observed across eight phage types, with resistance markers transferable via plasmids belonging to incompatibility group H1.

Conclusions:

• A significant proportion of S. typhi strains in Lima demonstrated multidrug resistance.
• Emerging antimicrobial agents show promise in treating resistant typhoid fever cases.
• Understanding resistance patterns and plasmid-mediated transfer is crucial for disease control.