Antibiotic Susceptibility Pattern of Salmonella Enterica Serovar Typhi and Paratyphi a from North India: the Changing Scenario

Enteric fever prevails as a major public health problem despite the use of antimicrobials due to the emergence of drug resistance. The present study was undertaken to find out the antimicrobial susceptibility pattern of Salmonella isolates from our region. Antimicrobial susceptibility testing for six drugs chloramphenicol (30μg), amoxicillin (10μg), cotrimoxazole (1.25/23.75μg), nalidixic acid (30μg), ciprofloxacin (5μg), and ceftriaxone (30μg) was done by the Kirby Bauer disc diffusion method. E-test was performed to calculate the MIC of ciprofloxacin. A total of the 80 Salmonella species was isolated which comprised of 51 (63.8%) Salmonella enterica serovar Typhi and 29 (36.2%) Salmonella enterica serovar Paratyphi A. All the isolates were nearly susceptible to the first line drugs, and none was multi drug resistant.Nalidixic acid resistance was high being 96% in Salmonella typhi and 100% in Salmonella paratyphi A. In Salmonella typhi 17.6% isolates were resistant to ciprofloxacin by the disc diffusion technique whereas 47% were resistant by the E-test. Similarly in Salmonella paratyphi A 48.3% were detected resistant by the Etest. Reduced susceptibility to ciprofloxacin indicating higher MIC to ciprofloxacin was seen in 49 % isolates of Salmonella typhi and 51.7% in the other serotype. These isolates are undetected by the routine disc diffusion techniques and result in treatment failure cases. It is pertinent to mention that MIC of ciprofloxacin by the E-test is more beneficial to assess the true pattern of resistance.