Resistance to Fluoroquinolones and Other Antimicrobials in Culture-Positive Salmonella typhi Isolates in Gulbarga, South India

Abstract

Background: Typhoid fever is a major public health concern in developing countries. The upsurge in the occurrence of bacterial isolates that are resistant to nalidixic acid; with reduced susceptibility to ciprofloxacin in typhoidal Salmonellae constitutes a challenge to the clinician. Methods: In order to better understand the epidemiology of Salmonella infections in South India, Salmonella typhi isolates were screened from various healthcare centers. Salmonella isolates were identified by using standard phenotypic, serological, antibiotic susceptibility and molecular methods. Results: Among a total of 100 S. typhi isolates 9% were found to be multidrug resistant and 30% were nalidixic acid resistant. Isolates with reduced susceptibility to ciprofloxacin displays single base mutations in the gyrA gene. A very low rate of 1% resistance was found to ciprofloxacin. The only one isolate with ciprofloxacin MIC ≥ 4 μg/ml also showed single mutation in the QRDR of the gyrA gene in S. typhi (GenBank accession no. HQ176349-HQ176368). Conclusions: A very low rate of nalidixic acid resistance with reduced susceptibility to ciprofloxacin was observed in comparison to other endemic areas in isolates of S. typhi from Gulbarga, South India, with steadily increasing NAR S. typhi but decreasing MDR isolations over the study period. This is most likely due to an increased use of ciprofloxacin as a first line drug of choice over more traditional antimicrobial agents for the treatment of typhoid fever.