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Widespread occurrence of multiple drug-resistant Salmonella typhi in India
E J Threlfall1, L R Ward, B Rowe
1WHO Collaborating Centre for Phage Typing and Resistance in Enterobacteria, Central Public Health Laboratory, London, UK.
Abstract:
Sixteen multiple drug resistant strains of Salmonella typhi belonging to Vi-phage types E1 (14) and O (2) and isolated in Southeast India in 1991 were characterized. All strains were resistant to chloramphenicol and the majority to trimethoprim and ampicillin. In all strains these resistances were encoded by plasmids of the H1 incompatibility group with molecular weights ranging from 110 to 120 megadaltons. Physicians in European countries should be aware that treatment may fail if patients with typhoid fever who have recently returned from the Indian sub-continent are given first-line treatment with chloramphenicol, trimethoprim or ampicillin. With the possible exception of young children, ciprofloxacin is currently the best choice for treatment of such patients.
Insights
Multiple drug-resistant Salmonella typhi strains in India exhibit resistance to common antibiotics like chloramphenicol, trimethoprim, and ampicillin, encoded by plasmids. Ciprofloxacin is recommended for treating typhoid fever in travelers returning from the Indian subcontinent.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Typhoid fever remains a significant public health concern, particularly in regions with high rates of antibiotic resistance.
- Salmonella typhi strains in Southeast India have shown increasing resistance to conventional antimicrobial agents.
Purpose of the Study:
- To characterize multiple drug-resistant Salmonella typhi strains isolated in Southeast India.
- To identify the genetic basis of antibiotic resistance in these strains.
- To inform treatment guidelines for typhoid fever in travelers returning from endemic areas.
Main Methods:
- Phenotypic characterization of Salmonella typhi strains for antibiotic susceptibility.
- Plasmid profiling to determine the molecular weight and incompatibility group of resistance plasmids.
- Phage typing to classify the isolated strains.
Main Results:
- Sixteen multi-drug resistant Salmonella typhi strains (Vi-phage types E1 and O) were identified.
- All strains were resistant to chloramphenicol; most were resistant to trimethoprim and ampicillin.
- Antibiotic resistance was mediated by plasmids belonging to the H1 incompatibility group (110-120 megadaltons).
Conclusions:
- Physicians should be aware of high-level resistance in Salmonella typhi from the Indian subcontinent to first-line antibiotics.
- Treatment failures are likely with chloramphenicol, trimethoprim, or ampicillin in patients returning from this region.
- Ciprofloxacin is suggested as a preferred treatment option, with caution for young children.