Genetic diversity of clinical strains of Salmonella enterica serovar Typhimurium

Aims: Salmonella spp. is one of the most common pathogenic bacteria responsible for gastroenteritis in human. Among Salmonella spp., S. typhimurium has many hosts other than humans and its prevalence rate is high in society. The aim of this study was to determine the ribotype diversity of S. typhimurium stains isolated in some hospitals of Tehran, Iran. Methods: In this descriptive study, clinical samples were collected from different hospitals in Tehran were investigated. Bacterial isolation was carried out by standard procedures in selective culture media and identification was achieved through biochemical and serological methods. DNA extraction was performed by phenol-cholorophorm methods. Ribotyping was used for molecular typing of S. typhimurium clinical isolates. Results: The sizes of the ribotyping bands ranged from 1.4 to 16.8 kb in all ribotypes. The S. typhimurium isolates were divided into 7 clusters based on the diversity of ribosomal genome areas. Most isolates (5 strains) belonged to the cluster 2b. Three isolates belonged to the 6b cluster and for the rest of isolates, each belhonged to one of other clusters. Conclusion: S. typhimurium strains circulating in the studied hospitals of Tehran, do not belong to a specific ribotype and have ribotype diversity, but other molecular typing methods should be implemented in order to make a more precise judjement about the presence of whether limited or widespread clones and the relationship among the different strains of this serotype.