The distribution of cytotoxic necrotizing factors (CNF-1, CNF-2, CNF-3) and cytolethal distending toxins (CDT-1, CDT-2, CDT-3, CDT4) in Escherichia coli strains isolated from extraitestinal infections and determination of their philogenetic relationship by PFGE

Determinants of extraintestinal infection in Escherichia coli remain unclear. Virulence factors making Extraintestinal pathogenic E.coli (ExPEC) different from other E.coli strains are the host cell adhesion, invasion, and two important factors/toxin, Cytotoxic Necrotizing Factor (CNF) and Cytolethal Distending Toxin (CDT) that are responsible for cell death. In the present study, CNF-CDT genotypes prevalences were investigated in 645 E. coli strains isolated from patients. This prevalences was analyzed with clinical origins, phylogroups and putative phylogenetic relationships. At least one virulence gene identified for ExPEC was found in 156 (20.7%) of 645 E. coli strains. Respectivly; 81, 20, 18 of ExPEC strains contained cnf1, cnf2, cnf3. Genes cdt1, cdt2, cdt3, cdt4 were detected 20, 4, 4, 4. At last two factors were detected cnf1-cnf3(n=6), cnf1-cdt1(n=6), cdt1-cdt3 (n=4). These 156 strains were found to be distributed in 106 large clusters by PFGE. Virulent ExPEC primarily related to groups B2 (60,8%) and D (30,7%). The CNF gene family is believed to enhance colonization of E. coli especially in the urinary system and these genes of the E. coli gene pool are gained in the ability to survive in new environment, such as the human urinary tract. The widespread diffusion of the CNF gene in E. coli help to distinguish ExPEC from commensal strains and these genes may be use spesific marker for noncommensal E. coli. Different strains of E. coli in terms of evolution have led to conclusion that have acquired ExPEC properties by acquiring different virulence genes resulting in deletion, recombination mutations and It is thought that infections caused by these strains was more likely community-acquired rather than hospital-acquired.