Phylogenetic Analysis of Salmonella spp. Isolated from Clinical Samples of Tehran's Hospitals Based on 23S rRNA Gene Sequence

  Salmonella Spp. is one of the most common causes of bacterial gastroenteritis and foodborne diseases. More than 2500 serotypes of Salmonella have been identified which most of them cause infections in humans.
Phylogenetic analysis of the family Enterobacteriaceae has not been subjected to extensive variation based on 16S rRNA sequences. In fact 16S rRNA gene was not thought to solve taxonomic problems concerning closely related species because of its highly degree of conservation in own structure. So, 23S rRNA gene which has a potential to classified related strains under sub-species level were candidate to analysis of Salmonella spp.
The aim of this study was to evaluate the clinical Salmonella strains’ relationship using
23S rRNA gene sequence. DNA of identified Salmonella spp. from patients with acute diarrhea was extracted. Sequences of 23S rRNA were determined after PCR tests. The whole gene sequences were used to generate phylogenetic trees based on Neighbor-joining method by MEGA 5.05 5. Helix (25 and 45) structures were detected in the most of different serotypes isolates. All S.Typhi included helix-25 in ribosomal structure, but in the other strains, helix-45 was also observed. The similarity between Salmonella spp. was 99-100% based on 23S rRNA. 23S rRNA gene sequence data was better to analyze at subspecies level and differentiation between serovars. According to variety in Salmonella serotypes based on difference in Anti gene O and H, application of new molecular methods and substituting them with traditional assays are needed.