Abstract
Objectives: Extensive drug resistance (XDR) typhoid fever, caused by resistance strain of Salmonella typhi, is an emerging public health concern in Pakistan. XDR typhoid fever severely limits the therapeutic options in outbreak cities of Pakistan. Antimicrobial resistance (AMR) surveillance has been carried out at study hospital in Karachi and here reporting the 15 months surveillance data.
Methods: A cross-sectional study was conducted on 969 Salmonella typhi isolates obtained from the blood culture samples of suspected typhoid fever cases at Kharadar General Hospital (KGH) from Jan 2018 to Mar 2019. Isolates were tested against 8 antimicrobial agents by quality controlled disk diffusion technique. Salmonella typhi Isolates resistance to first- line drugs; ampicillin, chloramphenicol, and co-trimoxazole referred as Multi-drug resistant (MDR), Whereas first-line, second-line drug (Ciprofloxacin) and third generation Cephalosporin (Ceftriaxone) resistance were considered as XDR.
Results: Of total 969 isolates, 777 (80%) were MDR showed resistance to all three first-line antibiotics and 517 (53%) were XDR resistant to five antibiotics (Ampicillin, Chloramphenicol, Co-trimoxazole, Ciprofloxacin and Ceftriaxone). Azithromycin and Imipenem were seen sensitive to all Salmonella typhi isolates (100%) among tested antibiotics. More than half of study S. typhi isolates 513 (53%) came from children under five years of age, among them 284 (55%) were XDR.
Conclusions: A large proportion of S. typhi isolates showed XDR-ST strain. Only Azithromycin and Imipenem were sensitive against XDR-ST strain. Current limited antibiotic option poses a serious threat of complete antibiotic failure in future against rapidly changing strain of S. typhi. J Microbiol Infect Dis 2020; 10(2):68-74.

Key words: Typhoid fever, Multi-drug resistance, Extensive-drug resistance, Salmonella typhi, Surveillance