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Objectives: This study aims to characterize at the molecular level the genes encoding resistance in Salmonella and explain the molecular mechanisms underlying resistance to ceftriaxone, cefepime, amoxicillin-clavulanate, tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, colistin and azithromycin in Salmonella. It aims as well to characterize the 16S rRNA gene region by restriction fragment length polymorphism (RFLP) to investigate if this region constitutes an appropriate ‘coincidental’ marker to distinguish important pathogenic Salmonella species. Finally, determine the lineages of Salmonella species and evolutionary relationships among bacteria classified within the same genus. Methodology: 246 Salmonella isolates were collected from children under 16 years old during Jan. 2018 - Dec 2019, presented with gastroenteritis at Hamad Medical Corporation. Isolates were tested for antibiotic susceptibility against nineteen relevant antibiotics using E-test. Isolates that harbor antibiotic resistance were confirmed using PCR specific primers for 38 genes. In addition, the variable region of class 1 and 2 integrons were identified by PCR among amoxicillin-clavulanate (AMC) resistant samples. RFLP targeting16S rRNAwas performed using seven restriction enzymes including AluI, Bgl I, Bgl II, EcoR I, SmaI, Hinf I & Hae III. Results: Resistance was detected against 15 antibiotics and (38.2%) of isolates were resistant to at least one antibiotic. Overall, high resistance was reported to tetracycline (23.9%), ampicillin (21.1%), AMC (18.7%) and sulfamethoxazoletrimethoprim (13%). Further, 22.4% of the isolates were multidrug-resistant (MDR), with 4.1% being ESBL producers. 90 % of ESBL producers had one of bla CTX-M-Group. Class (1) AMC resistant samples showed the highest resistance to different antibiotics. 16S rRNA-RFLP analysis divided Salmonella isolates into two main groups. Conclusion: Our results indicate a high antimicrobial resistance pattern of Salmonella, which necessities the development of regulatory programs to combats antimicrobial resistance. In particular, our results showed high resistance to Class (1) AMC cassette that involves the transmission and expression of the resistance. This might lead to a concern of increased multidrug resistance in the future. This study provides evidence guidance to activate and implement the pillars of an antimicrobial stewardship program in animal and human health to reduce MDR salmonellosis. |
