Molecular characterization of extensively drug-resistant Salmonella serovar Typhi in patients with gastrointestinal complications in Quetta, Pakistan

Extensive drug resistance (XDR) S. typhi have been evaluated in patients with gastrointestinal disturbance who attended multiple tertiary care hospitals in Quetta, Balochistan, Pakistan. Blood samples of total of 480 patients were obtained and S. typhi was isolated and verified by PCR. Isolates were subjected to antimicrobial susceptibility testing and antimicrobial resistance (AMR) genes of 1st, 2nd line antibiotics, 3rd generation cephalosporin and azithromycin were identified by PCR. Among 65 PCR confirmed S. typhi cases, 18(27%) were Multidrug resistance (MDR), 25(38%) XDR, 13 (20%) Extended spectrum ?-lactamase (ESBL) and only 4(6%) Azithromycin-resistant XDR S. typhi. The high frequency was observed for the antibiotics-resistant genes catA1, blaTEM-1 (100%), dhfr7 (95%), sul1 (98%), gyrA, gyrB, parC (93%) and qnrS and parE 100% each. The frequency of blaCTX-M-15 and acrB were 78% and 6% respectively. We found high burden of MDR, XDR and ESBLs S. typhi. The AMR genes were similar to those of the regional countries. Azithromycin resistance was low could be a drug of choice against XDR S. typhi in the study area. The study provided the molecular profile of AMR S. typhi in Quetta, capital of Balochistan province of Pakistan.