PHYLOGENETIC ANALYSES AND MULTILOCUS SEQUENCE TYPING (MLST) OF E. COLI STRAINS FROM NATIONAL E. COLI REFERENCE LABORATORY

Background and Aim:Bacteremia represents one of the significant causes of death in the developed countries and among Gram-negative bacteria. Escherichia coli represent the first cause of bacteremia, with 30% of the total number of bacteremia due to this pathogen. Phylogenetic analysis suggested that E. coli can be divided into four major groups (A, B1, B2 and D). Multilocus Sequence Typing (MLST), in which internal portions of multiple housekeeping genes are sequenced to define clonal diversity, has emerged as a powerful tool to describe the genetic structure of bacterial populations.Methods:50 E. coli strains from National E. coli Reference Laboratory were used. Total DNA was isolated from overnight culture strains. Primer pairs were designed for PCR amplification and sequencing of internal portions of eight housekeeping genes (dinB, icdA, pabB, polB, putP, trpA, and trpB). All PCR products were thus sequenced using the same two sequencing primers. Bionumerics software version 7.6 was used for MLST analysis of 5 selected strains.Results:The internal portions of eight selected housekeeping genes were sequenced in defined isolates; the results highlighted the strong phylogenetic clustering of E. coli strains into five separated branches. PCR results show that STEC (Shiga-toxin-producing E. coli) strains were PCR-negative for some housekeeping genes and these strains were also PCR-negative for put primer. Conclusion:In conclusion, MLST and defined Sequence Type (ST) of each group can be used for clonal diversity determination of E. coli clinical isolates.

کلیدواژه ها:

Multilocus Sequence Typing ، E. coli strains ، Phylogenetic analysis