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Multidrug resistant Salmonella typhi in Calicut, south India
J Sudarsana1, L Nair, K I Devi
1Department of Microbiology, Medical College, Calicut.
Abstract:
Eighty S. typhi strains isolated during the period of one year (July 1989 to June 1990) were tested for susceptibility to chloramphenicol, ampicillin, cotrimoxazole, gentamicin, kanamycin, cefazolin, furazolidone and ciprofloxacin. Determination of minimum inhibitory concentration (MIC) by tube dilution method showed that the multiply resistant S. typhi strains were resistant to chloramphenicol and ampicillin up to a concentration of 1000 micrograms/ml. MIC of sulphamethoxazole was found to be 800 micrograms/ml and trimethoprim 160 micrograms/ml. The presence of R plasmid was demonstrated by resistance transfer experiments using Esch. coli K12 (F-Lac+Nal-) as the recipient. On phage typing, most of the multiresistant S. typhi isolates were found to belong to phage type E1.
Insights
This study found that most multi-drug resistant Salmonella Typhi strains were resistant to chloramphenicol and ampicillin. Resistance transfer experiments confirmed the presence of R plasmids in these Salmonella Typhi isolates.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Salmonella Typhi (S. typhi) is a significant cause of typhoid fever globally.
- The emergence of multi-drug resistant (MDR) strains poses a major public health challenge.
- Monitoring antimicrobial susceptibility patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the antimicrobial susceptibility profiles of S. typhi strains isolated over a one-year period.
- To investigate the mechanisms of resistance, including plasmid-mediated resistance.
- To characterize the phage types of MDR S. typhi isolates.
Main Methods:
- Antimicrobial susceptibility testing using the tube dilution method to determine Minimum Inhibitory Concentrations (MICs).
- Resistance transfer experiments using Escherichia coli K12 as a recipient to identify R plasmids.
- Phage typing to classify S. typhi isolates.
Main Results:
- Eighty S. typhi strains were analyzed for susceptibility to eight antibiotics.
- MDR S. typhi strains exhibited high resistance to chloramphenicol and ampicillin (MIC up to 1000 µg/ml).
- Significant MICs were observed for sulphamethoxazole (800 µg/ml) and trimethoprim (160 µg/ml).
- R plasmids were confirmed through resistance transfer experiments.
- Most MDR S. typhi isolates belonged to phage type E1.
Conclusions:
- The study highlights the prevalence of MDR S. typhi strains resistant to common antibiotics like chloramphenicol and ampicillin.
- R plasmids play a role in the dissemination of antimicrobial resistance in S. typhi.
- Phage type E1 appears to be associated with multi-drug resistance in these isolates, informing surveillance and control efforts.