Comparison and phylogenetic analysis of the ISS gene in two predominant avian pathogenic E. coli serogroups isolated from avian colibacillosis in Iran.

The ISS (increased serum survival) gene and its protein product (ISS) of avian pathogenic Escherichia coli (APEC) are important characteristics of resistance to the complement system. The aims of this study were to clone, sequence and characterize sequence diversity of the ISS gene between two predominant serogroups in Iran and among those previously deposited in Genbank. The ISS gene of 309 bp from the APEC χ1390 strain was amplified by PCR, cloned and sequenced using pTZ57R/T vector. The ISS gene from the χ1390 strain has 100% identity among different serogroups of APEC in different geographical regions throughout the world. Phylogenetic analysis shows two different phylogenic groups among the different strains. Strong association of nucleotide sequences among different E. coli strains suggests that it may be a conserved gene and could be a suitable antigen to control and detect avian pathogenic E. coli, at least in our region. Currently, our group is working on the ISS protein as candidate vaccine in SPF poultry.