Antimicrobial Susceptibility Pattern of Typhoidal Salmonella Species in Tertiary Hospitals of Dhaka City

Enteric fever caused by Salmonella enterica remains an unresolved public health problem and due to the prevalence of multidrug resistant (MDR) strains for the last two decades, the first line antimicrobials were discontinued and currently the second line antimicrobials are used. A total of 325 blood samples from clinically suspected enteric fever patients were collected during the study period of July, 2014 to June, 2015. After identification of organisms, antimicrobial susceptibility tests were done by disc diffusion method and MIC by broth microdilution method. Rate of isolation of organisms were 19.38%, among them Salmonella Typhi were 85.71% and Salmonella Paratyphi A were 14.29%. About 74.07%, 77.78% and 72.22% strains of Salmonella Typhi and 88.89%, 77.78% and 77.78% strains of Salmonella Paratyphi A were sensitive to chloramphenicol, ampicillin and cotrimoxazole respectively. By disc diffusion method, 94.44% Salmonella Typhi strains and by broth microdilution method, 98.15% strains of Salmonella Typhi were sensitive to ceftriaxone. All the strains of Salmonella Paratyphi A were sensitive to ceftriaxone by both disc diffusion and broth microdilution method. In case of Salmonella Typhi, by disc diffusion method, 88.88% strains and by broth microdilution method, 92.59% strains were sensitive to cefotaxime. In case of Salmonella Paratyphi A, by both disc diffusion and broth microdilution method, 88.89% strains were sensitive to cefotaxime by each method. About 81.48% strains of Salmonella Typhi and 88.89% strains of Salmonella Paratyphi A were sensitive to cefixime by disc diffusion method. By disc diffusion method, 70.37% strains of Salmonella Typhi and by broth microdilution method, 72.22% Salmonella Typhi strains were intermediate sensitive to ciprofloxacin. By disc diffusion method, 66.67% strains of Salmonella Paratyphi A and by broth microdilution method, 77.78% strains of Salmonella Paratyphi A were intermediate sensitive to ciprofloxacin. All the strains of Salmonella Typhi and Paratyphi A were resistant to azithromycin by disc diffusion method but 87.04% strains of Salmonella Typhi and 77.78% strains of Salmonella Paratyphi A were sensitive by broth microdilution method. To determine antimicrobial susceptibility, broth microdilution method along with disc diffusion method should be done especially in case of azithromycin. Treatment of enteric fever with the first line antimicrobials should be reconsidered after testing their susceptibility pattern.