Revised ciprofloxacin breakpoints for Salmonella Typhi: its implications in India
1Department of Microbiology, Christian Medical College, Vellore, Tamil Nadu, India.
Abstract:
The rise of multidrug resistant strains of Salmonella Typhi in the last decade of the previous century led to the use of fluoroquinolones as the drug of choice. However, over the past few years fluoroquinolone resistance has been increasingly reported. In accordance with the revised Clinical and Laboratory Standards Institute (CLSI) breakpoints, only 3% of the isolates were susceptible to ciprofloxacin in comparison to 95% as per the earlier guidelines when 488 isolates collected between 2010 and 2012 were re-interpreted. Interestingly, re-emergence of strains susceptible to chloramphenicol, ampicillin and cotrimoxazole is being seen. Amidst the changing susceptibility profile, azithromycin remains a promising alternative.
Insights
Multidrug-resistant Salmonella Typhi strains show increasing fluoroquinolone resistance. Re-emerging susceptibility to older antibiotics is noted, with azithromycin remaining a key alternative.
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.
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