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Plasmid mediated multidrug resistance in Salmonella typhi
1Department of Microbiology, Christian Medical College Hospital, Vellore.
Abstract:
Between September 1989 and February 1991, strains of S. typhi showing multiple drug resistance were isolated from blood cultures of patients with typhoid fever. A total of 283 isolates were obtained over a period of 18 months. Forty four (11%) of these isolates were resistant to chloramphenicol, ampicillin, co-trimoxazole and tetracycline, the first three being drugs currently used in treating typhoid fever. Forty of the 44 multi-resistant strains tested showed transfer of resistance 'en block' to recipient Escherichia coli K 12 (J62-2). All 44 multi-resistant strains were sensitive to ciprofloxacin and ofloxacin. Since the resistance is plasmid-mediated, the problem is likely to get aggravated.
Insights
Multiple drug-resistant Salmonella Typhi strains emerged between 1989-1991. These resistant strains, often plasmid-mediated, were susceptible to newer antibiotics like ciprofloxacin, but resistance is likely to worsen.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Typhoid fever, caused by Salmonella Typhi, is a significant global health concern.
- The emergence of multidrug-resistant (MDR) strains poses a therapeutic challenge.
- Monitoring antimicrobial resistance patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To characterize the prevalence and resistance patterns of Salmonella Typhi isolates.
- To investigate the genetic basis of multidrug resistance in S. typhi.
- To assess the susceptibility of MDR strains to currently available antibiotics.
Main Methods:
- Isolation and identification of Salmonella Typhi from blood cultures of typhoid fever patients.
- Antimicrobial susceptibility testing using standard antibiotic panels.
- Plasmid-mediated resistance transfer experiments using conjugation with Escherichia coli K-12.
Main Results:
- 283 Salmonella Typhi isolates were collected between September 1989 and February 1991.
- 11% (44/283) of isolates exhibited MDR to chloramphenicol, ampicillin, co-trimoxazole, and tetracycline.
- Resistance was transferable 'en bloc' via plasmids in 40 of 44 MDR strains.
- All 44 MDR strains remained sensitive to ciprofloxacin and ofloxacin.
Conclusions:
- A significant proportion of S. typhi isolates displayed MDR to commonly used antibiotics during the study period.
- The plasmid-mediated nature of this resistance suggests a high potential for further dissemination.
- Fluoroquinolones like ciprofloxacin and ofloxacin represent effective therapeutic options against these MDR strains.