Detection of Salmonella typhi Isolates and Ceftriaxone Strains Harbouring CTX-M-15 Gene

Objective: To determine blaCTX-M-15(Cefotaxime-Munich) gene amongst the extensively drug resistant (XDR)Salmonella typhi (S. typhi) isolates by quantitative Polymerase Chain Reaction (qPCR). Study Design: Observational, cross-sectional study.Place and Duration of the Study: PNS Shifa Hospital and Bahria University of Health Sciences (BUHS), from January to June 2022. Methodology: All the patients clinically suspected of enteric fever, whose blood culture specimens yielded growth ofS. typhi were included in this study. These samples were confirmed by serotyping and biochemical reactions. The ceftriaxone resistance was evaluated by antibiotic susceptibility test according to CLSI 2020 guidelines, whereas blaCTX-M-15 gene was detected by (PCR) using gene specific primers.Results: Out of 149 S. typhi isolates, 87.2% were confirmed XDR S. typhi resistant to ceftriaxone (CRO). Among these, 83.9% harboured blaCTX-M-15 gene.Conclusion: There was a very high frequency of XDR S. typhi harbouring blaCTX-M-15 in Karachi, Pakistan.