Our study of significant bacteriurias indicated that the worldwide shift in the etiology of infections also holds true for the Florence area.

In a twenty-year period (1970-1990), we noted a decreased frequency of Gram-negative bacilli, particularly of the family Enterobacteriaceae, and a significant increase of Gram-positive cocci in urinary patients.

This finding was observed both in hospital and in community-acquired cases in the male sex and only in nosocomial bacteriurias in the female sex.

There was a reduced isolation of « classic » urinary pathogens such as Proteus mirabilis: its prevalence in hospital-acquired urinary tract infection (UTI) decreased from 16% in 1970 to 5% in 1990 both in males and in females.