Vero cell invasiveness of Proteus mirabilis

Vero cell invasiveness was studied for a group of Proteus mirabilis strains isolated from the urinary tract and feces and for a limited group of urinary isolates of Escherichia coli. Experimental conditions affecting this invasiveness were studied. All of the P. mirabilis strains tested were capable of cell invasion, whereas none of the E. coli strains was. Correlation between the hemolytic activity of the P. mirabilis strains and their invasive ability suggested that the bacterial hemolysin may be involved in the invasion process. Other experimental evidence supporting this hypothesis is discussed. The differences in the invasive capacities of P. mirabilis and of E. coli may be important for the apparent differences in the pathogenesis of urinary tract infection by both species.