Investigation of Antimicrobial Resistance Genes and Clonal Relatedness of Outbreak-Associated Salmonella Enteritidis Isolates Using PFGE.

PURPOSE: Salmonella Enteritidis is one of the most common causes of gastroenteritis outbreaks. Detailed characterization of outbreak-associated isolates is essential for understanding local epidemiology, antimicrobial resistance patterns, and transmission dynamics. Epidemiological investigations of these strains can help to control the spread of this bacterium. METHODS: In the current study, 27 strains of S. Enteritidis were isolated from patients with gastroenteritis. Antibiotic resistance of these strains was determined using phenotypic and genotypic methods. Biofilm formation ability was evaluated using the microtiter method. The strains were clustered using pulsed-field gel electrophoresis (PFGE) with AvrII. RESULTS: The highest rate of antibiotic resistance was associated with cefuroxime (74.1%). Five antibiotic-resistance genes were detected, and all of them were bla TEM. Of 27 strains, 96.3% were biofilm producers. According to PFGE results, the studied strains were all included in one clone. CONCLUSION: This study provides data on the antimicrobial susceptibility and high biofilm-forming capacity of outbreak-associated S. Enteritidis isolates in Iran. The limited genetic diversity observed by PFGE highlights the clonal nature of these strains and suggests that combining PFGE with additional DNA-based methods is beneficial for an accurate diagnosis.