The Antibiotic Resistance Pattern and Prevalence of blaTEM, blaSHV, blaCTX-M, blaPSE-1, sipB/C, and cmlA/tetR Genes in Salmonella typhimurium Isolated from Children with Diarrhea in Tabriz, Iran

Salmonella gastroenteritis is a global health concern. Recently, increased resistance to Salmonella typhimurium has been reported in several countries.

The present study aimed to evaluate the prevalence of blaTEM, blaSHV, blaCTX-M, blaPSE-1, sipB/C, and cmlA/tetR genes in S. typhimurium isolates and determine their antibiotic resistance.

This cross-sectional descriptive study was conducted on 110 fecal samples, which were collected from the patients referred to the hospitals and medical centers in Tabriz, Iran during eight months. After phenotypic identification, the antibiogram test and double-disc synergy test were performed on the isolates. Following that, the prevalence of resistance genes was evaluated using multiplex PCR and specific primers.

Out of 110 fecal samples, 26 samples (23.63%) were positive for S. typhimurium. The highest resistance of the isolates was against ceftazidime, cefotaxime, amikacin, and tetracycline (100%), and the lowest resistance was against imipenem (3.85%) and nalidixic acid (7.69%). In total, 15 S. typhimurium isolates (57.69%) were positive for the extended-spectrum beta-lactamases. In addition, the most common resistance genes in the isolates were cmlA/tetR (38.46%), blaTEM (34.61%), and blaCTX-M (26.92%). Four isolates (15.38%) carried sipB, three isolates (11.53%) contained blaSHV, and two isolates (7.69%) carried blaPSE-1.

The obtained results indicated the high prevalence of antibiotic-resistant S. typhimurium. Therefore, the identification of resistance genes is an important strategy for identifying and counteracting antibiotic resistance.