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Updated: Apr 30, 2026
An Allelotyping PCR for Identifying Salmonella enterica serovars Enteritidis, Hadar, Heidelberg, and Typhimurium
Published on: July 22, 2011
A study of antibiogram of Salmonella enterica serovar Typhi isolates from Pondicherry, India
Sreenivasan Srirangaraj1, Arunava Kali1, M V Pravin Charles1
1Department of Microbiology, Mahatma Gandhi Medical College & Research Institute, Pondicherry.
Background:
Enteric fever caused by Salmonella enterica serovar Typhi (S. Typhi) is an important public health problem in developing countries like India.1 The emergence of resistance to fluoroquinolones has reduced the therapeutic options available. Currently, the uniform laboratory interpretation of ciprofloxacin and azithromycin susceptibility remains unclear.
Aims:
To study the antibiogram of S. Typhi isolates with special emphasis on in-vitro activity of ciprofloxacin and azithromycin.
Method:
We evaluated the antimicrobial susceptibility pattern of 16 S. Typhi isolates from January 2012 to June 2013. We also determined by Epsilometer-test (E-test) method, the minimum inhibitory concentration (MIC) of ciprofloxacin and azithromycin against these isolates and compared them with their corresponding disc diffusion sizes.
Results:
Fifteen (93.75 per cent) isolates were sensitive to chloramphenicol, 14 (87.5 per cent) were sensitive to cotrimoxazole. All isolates were resistant to nalidixic acid. MICs for ciprofloxacin ranged from 6μg/ml to 15μg/ml and corresponding zone diameters ranged from 15mm to 26mm. MIC and zone diameters for ciprofloxacin had significant negative correlation. MICs for azithromycin ranged from 3μg/ml to 24μg/ml, corresponding zone diameters ranged from 13mm to 19mm. However, MIC and zone diameters for azithromycin had no significant negative correlation.
Conclusion:
The widespread emergence of resistance to fluoroquinolones and reappearance of sensitivity to firstline drugs has reinforced the need for antibiotic recycling. There is a need to have uniform laboratory testing guidelines for testing susceptibility to ciprofloxacin and azithromycin for S. Typhi isolates.
Insights
Salmonella Typhi resistance to fluoroquinolones is rising, impacting treatment options. This study highlights the need for standardized lab testing for ciprofloxacin and azithromycin susceptibility in S. Typhi isolates.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Enteric fever, caused by Salmonella enterica serovar Typhi (S. Typhi), poses a significant public health challenge in developing nations.
- Increasing resistance to fluoroquinolones limits treatment choices for S. Typhi infections.
- Current laboratory interpretation of ciprofloxacin and azithromycin susceptibility for S. Typhi remains inconsistent.
Purpose of the Study:
- To investigate the antimicrobial susceptibility patterns of S. Typhi isolates.
- To specifically evaluate the in vitro activity of ciprofloxacin and azithromycin against S. Typhi.
Main Methods:
- Antimicrobial susceptibility testing was performed on 16 S. Typhi isolates.
- Minimum Inhibitory Concentrations (MICs) for ciprofloxacin and azithromycin were determined using Epsilometer-test (E-test).
- MICs were correlated with disc diffusion zone sizes for both antibiotics.
Main Results:
- High sensitivity rates were observed for chloramphenicol (93.75%) and cotrimoxazole (87.5%).
- All isolates exhibited resistance to nalidixic acid.
- Significant negative correlation found between ciprofloxacin MICs and zone diameters, unlike azithromycin.
Conclusions:
- The rise in fluoroquinolone resistance and return of sensitivity to older drugs necessitate antibiotic recycling strategies.
- Development of uniform laboratory guidelines for S. Typhi susceptibility testing to ciprofloxacin and azithromycin is crucial.
