Characterization of genetic diversity among clinical strains of Salmonella enterica serovar infantis by ribotyping method

Background and Objective: Salmonella spp. are enteric pathogens with a worldwide distribution comprising a large number of serovars characterized by different hosts and distribution. Among Salmonella spp., the number of infections and diseases caused by the serotype Salmonella enterica serovar Infantis started to increase significantly in the last decade. The aim of this study was to investigate the genetic diversity of the clinical stains of Salmonella enterica serovar Infantis isolated in Tehran, Iran by using the Ribotyping method. Materials and Methods: In this descriptive study from November 2007 to December 2010, clinical samples, collected from different hospitals in Tehran, were investigated for detection of Salmonella enterica serovar Infantis. Bacterial isolation and identification was achieved through biochemical and bacteriological methods. The Ribotyping technique was applied for the molecular typing of the strain of Salmonella enterica serovar Infantis. Results: Out of the 26 Salmonella serogroup C samples isolated in this study, 19 strains (73%) belonged to Salmonella enterica serotype Infantis. Ribotyping results divided Salmonella enterica serovar Infantis stains into 9 clusters (1c to 9c). The majority (7) of the strains belonged to cluster 1c. Conclusion: The results obtained from the Ribotyping patterns indicate that Salmonella enterica serovar Infantis strains, circulating among the patients in Tehran, belong to a diverse number of clones. Moreover, our data show that Ribotyping is an appropriate method for the molecular typing of Salmonella enterica serovar Infantis strains

Detection of Escherichia coli, Salmonella enterica and shigella Dysenteriae by analysis of 23s ribosomal DNA gene

Background: Ribosomal DNA (rDNA) genes contain signature structures which are unique for groups of organisms. Considering their great number in cells and their protected areas, they render ideal targets for specific nucleic acid probes. The present study aimed to investigate the capability of some specific regions of 23S rDNA gene as a DNA target for differentiation and screening of Escherichia coli, Salmonella enterica, and Shigella dysenteriae. Methods: Bacterial reference strains used in this study were E. coli, S. enterica and Sh. dysenteriae that were provided by the centers for microbial culture collection (CMCC) at Pasture Institute of Iran. DNA extraction was performed by boiling method. Alignment of the 23S rDNA sequences of bacterial species was performed by using AlignX (a component of Vector NTI Advance 11.0) and areas displaying sequence divergence among species were used for designing universal primers and individual bacteria specific probe. Findings: The universal polymerase chain reaction (PCR) products of each bacterial species showed bands of approximately 880 bp to be being equivalent to the fragment size of 23S rDNA gene. Different size bands of 23S rDNA probes were produced and included 228 bp for E. coli, 444 bp for S. enterica, and 776 bp for Sh. dysenteriae. Conclusion: Comparative sequence analysis of variable and specific regions of 23S rDNA genes among the studied bacterial species showed that we were able to amplify specific target among universal region for the detection of many enteric pathogenic bacteria