Molecular Characterization of Plasmid-mediated Quinolone Resistant Salmonella typhi From Patients Attending Federal Medical Center, Jabi, Abuja, Nigeria

Aims: This study investigates and reports the detection of qnr genes (plasmid-mediated quinolone resistance PMQR) in S.typhi isolated from stool of patients with suspected typhoid fever, in Federal Medical Center, Jabi, Abuja, Nigeria. Study Design:  Cross sectional study. Place and Duration of Study: Department of Microbiology, Nasarawa State University, Keffi, between October 2022 and November 2023. Methodology: Salmonella typhi was isolated from stool of patients with suspected typhoid fever using standard culture and microbiological methods. Antibiotic susceptibility testing were performed  using  the  disc  diffusion method  to  investigate  the  ability  of  S.  typhi to resist some antibiotics. Qnr genes (qnrC,qnrD,qnrS) were detected by PCR and amplification. Results: 17 out of 150 (11.3%) of the samples collected had S.typhi. Antibiotic resistance in the isolates in decreasing order were as follows: cefotaxime (100.0%), amoxicillin/ clavulanic acid (94.1%), nalidixic acid (94.1%), cefuroxime (94.1%), imipenems (88.2%), ceftriaxone/sulbactam (82.4%), ciprofloxacin (82.4%), gentamicin (58.8%), levofloxacin (47.1%) and ofloxacin (29.4%).The commonest antibiotic resistant phenotype was AUG- CTX-IMP-OFX-CN-NA-CXM-CRO-CIP-LBC at 29.4%. Multiple antibiotic resistance (MAR) was observed in 100% (17/17) of the isolates with the common MAR indices being 1.0 (29.4%), 0.7 (23.5%), 0.8 (17.6%) and 0.5 (17.6%). 33.3% of the isolates in FMCJ were positive for qnrC,qnrD,qnrS,qnrA+qnrC and qnrS+ aac(6′)-Ib-cr as all of qnrC qnrD,and qnrS genes were all expressed in the isolates. Conclusion: The S.  typhi isolates showed lower resistances to ofloxacin, levofloxacin, and gentamicin, and all isolates were MAR, with resistance to 10 antibiotics being the most predominant. In addition, qnrC,qnrD, and qnrS resistance genes were all expressed in the isolates.