Revised ciprofloxacin breakpoints for Salmonella Typhi: its implications in India

Area of Science:

• Microbiology
• Infectious Diseases
• Pharmacology

Background:

• Multidrug-resistant Salmonella Typhi emerged, leading to fluoroquinolone use.
• Increasing fluoroquinolone resistance in Salmonella Typhi strains is a growing concern.

Purpose of the Study:

• To evaluate the changing antimicrobial susceptibility patterns of Salmonella Typhi.
• To assess the effectiveness of various antibiotics against current Salmonella Typhi isolates.

Main Methods:

• Re-interpretation of susceptibility data from 488 Salmonella Typhi isolates (2010-2012) using revised Clinical and Laboratory Standards Institute (CLSI) breakpoints.
• Analysis of resistance trends for fluoroquinolones, chloramphenicol, ampicillin, and cotrimoxazole.

Main Results:

• Only 3% of isolates were susceptible to ciprofloxacin under new CLSI guidelines, compared to 95% under older guidelines.
• A re-emergence of susceptibility to chloramphenicol, ampicillin, and cotrimoxazole was observed.
• Azithromycin demonstrated continued effectiveness against the tested isolates.

Conclusions:

• Salmonella Typhi exhibits evolving antimicrobial resistance, particularly to fluoroquinolones.
• Older antibiotics like chloramphenicol, ampicillin, and cotrimoxazole may regain clinical utility.
• Azithromycin is a viable therapeutic option for Salmonella Typhi infections amidst changing resistance patterns.