A study of antibiogram of Salmonella enterica serovar Typhi isolates from Pondicherry, India

Srirangaraj Sreenivasan, Arunava Kali, MV Pravin Charles


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. 

To study the antibiogram of S. Typhi isolates with special emphasis on in-vitro activity of ciprofloxacin and azithromycin.

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.

Fifteen (93.75 per cent) isolates were sensitive to chloramphenicol, 14 (87.5 per cent) were sensitive to co-trimoxazole. All isolates were resistant to nalidixic acid. MICs for ciprofloxacin ranged from 6 μg/ml to 15 μg/ml and corresponding zone diameters ranged from 15 mm to 26 mm. MIC and zone diameters for ciprofloxacin had significant negative correlation. MICs for azithromycin ranged from 3 μg/ml to 24 μg/ml, corresponding zone diameters ranged from 13 mm to 19 mm. However, MIC and zone diameters for azithromycin had no significant negative correlation.

The widespread emergence of resistance to fluroquinolones and reappearance of sensitivity to first-line 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.

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