Current pattern in antimicrobial susceptibility of Salmonella Typhi isolates in Pondicherry

Typhoid fever continues to remain a health problem as the causative organism Salmonella Typhi has developed resistance to many of the antibiotics used. This study was undertaken to determine the current pattern of resistance to antimicrobial agents and phage types of S.Typhi isolates obtained in a tertiary health care hospital in Pondicherry. Blood culture was done for 1296 suspected cases of enteric fever and 157 strains of S. Typhi were isolated. Sensitivity to ampicillin, chloramphenicol, gentamicin, ciprofloxacin and ceftriaxone was determined by disc diffusion, and the minimum inhibitory concentration (MIC) of ciprofloxacin determined. There were 61 multidrug resistant (MDR) isolates. The MIC of ciprofloxacin for 147 isolates was >0.5 mg/l; of these, 131 were resistant to nalidixic acid. Phage typing was done for 123 isolates and 115 were found to be of phage type E1, biotype 1. A decline in the number of MDR isolates was noted. Concurrently, there has been an increase in the number of isolates sensitive to all antibiotics except nalidixic acid, and all these isolates showed reduced susceptibility to ciprofloxacin. Nalidixic acid susceptibility could be a useful screening test for the detection of decreased susceptibility of S. Typhi to ciprofloxacin. The clinicians should be advised to use ceftriaxone selectively in cases showing non-responsiveness to ciprofloxacin.