[Urinary tract infections: bacteriological aspects of recurrent cystitis].

Gram-negative bacteria, and above all E. coli and Proteus sp., cause the great part of UTI. Some characters of microorganisms (as the capsular K antigen, the production of haemolysin and the endotoxin of cell wall) can affect the invasive capacity and the virulence of E. coli. The bacterial adherence, due to the presence of fimbriae, seems to be correlated to the persistence of microorganisms in lower urinary tract. Moreover Enterobius vermicularis, intestinal parasite frequent in infancy, can transport in girls E. coli strains from the rect, through the urethra, to the bladder. The data regarding the importance of the immune local response are not clear yet.