Pathogenicity Islands of Uropathogence E. Coli and Evolution of Virulence

E. coli bacteria are able to cause a large range of infectious diseases in humans. Among these are infections of the gastrointestinal tract as well as extraintestinal infections of great importance. Intestinal E. coli can be grouped in at least six different pathotypes including enterotoxigenic (ETEC), enteropathogenic (EPEC), enterohemorrhagic (EHEC) and enteroaggregative (EaggEC) E. coli. Extraintestinal E. coli fall into three groups: meningitis (MENEC), septicemia (SEPEC) and uropathogenic (UPEC) E. coli. UPECs are by far the most common cause of uncomplicated bacterial urinary tract infections (UTIs). About 80 % of all UTIs are due to E. coli. UPECs differ from non-pathogenic E. coli variants by the presence of certain virulence factors which contribute to their ability to cause disease. These are two different types of toxins, α -hemolysin (Hly) and the cytotoxic necrotizing factor 1 (CNF1), fimbrial adhesins e. g. P-, type 1 and S-fimbriae and iron-uptake systems like aerobactin, enterobactin or yersiniabactin. Furthermore, UPECs belong to certain serotypes and have the capacity to survive in human serum. About ten years ago it was detected that UPECs contain distinct blocks of DNA carrying closely linked virulence genes. Later on these structures were