Incidence and antimicrobial resistance profile of multi-drug resistant Salmonella typhi isolated from blood samples in Khyber Pakhtunkhwa, Pakistan

Abstract

Salmonella typhi has shown increasing resistance to antibiotics in recent years, creating serious challenges in treatment. Inappropriate use of antibiotics without testing bacterial sensitivity often results in therapeutic failure, highlighting the importance of bacterial isolation and susceptibility testing. A study was carried out from July 2022 to July 2023 to assess the incidence of multidrug-resistant (MDR) S. typhi in clinical samples and evaluate its susceptibility profile across different districts of Khyber Pakhtunkhwa, Pakistan.

A total of 1,625 blood samples were collected from patients with suspected enteric fever in Peshawar, Dir, Mardan, and Swat. Of these, 341 isolates (20.98 %) were confirmed as S. typhi using biochemical tests and PCR amplification of the fliC gene. Infection was more common in males (57.7 %), while children ≤10 years were most affected (54.25 %). Seasonal distribution revealed highest prevalence in summer (38.41 %). Among districts, Peshawar reported the highest occurrence (78.29 %), followed by Dir (14.36 %) and Mardan (7.03 %). A significant correlation was found between districts and infection rate, though age and gender showed no significant association.

Antimicrobial testing revealed high susceptibility to meropenem (90.71 %) and tetracycline (71.83 %), but marked resistance to ampicillin (77.40 %), co-trimoxazole (74.61 %), ceftriaxone (73.68 %), and erythromycin (71.52 %). Notably, 71.94 % isolates were MDR and 22.38 % were extensively drug-resistant (XDR). PCR detection confirmed high prevalence of resistance genes, particularly blaTEM (61 %), sul2 (76 %), and sul1 (57 %).

This study underscores the alarming rise of MDR S. typhi in Khyber Pakhtunkhwa and stresses the urgent need for effective surveillance, prevention, and antimicrobial stewardship.