Genotype Cluster Analysis in Pathogenic Escherichia coli Isolates Producing Different CDT Types.

Diarrheagenic and uropathogenic E. coli types are mainly characterized by the expression of distinctive bacterial virulent factors. stx1, stx2 (Shiga toxins), and cdt (cytolethal distending toxin) genes have been acquired by horizontal gene transfer. Some virulent genes such as espP (serine protease), etpD (part of secretion pathway), and katP (catalase-peroxidase), or sfpA gene (Sfp fimbriae), are on plasmids and the others like fliC (flagellin) and the fimH gene (fimbriae type-I) are located on chromosome. Genomic pathogenicity islands (PAIs) carry some virulent genes such as hly gene. To determine the existence of virulence genes in cdt clinical isolates, genes including stx1, stx2, cdt, hly, espP, katP, sfpA, etpD, fliC, and fimH were assessed by Polymerase Chain Reaction (PCR). The most prevalent isolates for etpD and katP genes were 85.7% in cdtII. katP gene was also observed 83.3% in cdtI. However, in 42.85% of cdtIII isolates, espP gene was the most detected. Moreover, hly gene was also the most prominent gene in cdtIII (71.42%). sfpA gene was observed in 66.6% of cdtV. stx1 gene was detected in 100% of cdtII, cdtIV, and cdtV types. Presence and pattern of virulence genes were considered among cdt positive isotypes and used for their clustering and profiling.