Vero cell invasiveness of Proteus mirabilis

P G Peerbooms, A M Verweij, D M MacLaren
1984 Infection and Immunity  
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
more » ... terial 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. Proteus mirabilis and Escherichia coli are important pathogens of the urinary tract (6). Several properties of both species, especially of E. coli, have been studied in relation to virulence for the urinary tract. The importance of the P. mirabilis urease as a virulence factor, both in human and experimental urinary tract infections, is well documented (10, 11, 13). The importance of other possible virulence factors of P. mirabilis such as adhesive ability (20) , the possession offlagellae (15), and sensitivity to the bactericidal effect of human serum (9) is much less clear. As there is an increasing interest in cell invasiveness as an important step in the pathogenesis of infections by different bacteria (7, 12, 14, 19) , we decided to study invasiveness by P. mirabilis as a part of the study of virulence factors of P. mirabilis in urinary tract infections. In 1960, Braude and Siemienski (3) described the invasion of a P. mirabilis strain in mammalian cells both in vivo and in vitro. A urinary strain of E. coli did not show this ability to invade cells. Except for a confirmation by Silverblatt (20) , little attention has been paid to this phenomenon. Other authors have also reported differences in the pathogenesis of urinary tract infections by both species in experimental models. Infections caused by P. mirabilis tend to be more persistent than infections caused by E. coli (5). Renal infections are more easily established with P. mirabilis than with E. coli in mice (16, 22) . The purpose of the present study was to investigate the experimental conditions affecting cell invasiveness by P. mirabilis. We also investigated the possible role of the P. mirabilis hemolysin in the invasion process since Kihlstrom and Edebo (8) suggested that surface-bound catalysts on bacteria might enhance invasion. Furthermore, we tested a group of urinary isolates of E. coli to confirm the observation of Braude and Siemienski (3) on the lack of invasive ability of a urinary strain of E. coli. MATERIALS AND METHODS Bacterial strains. The P. mirabilis strains used in this study were isolated from the urine of patients with urinary tract infections or from the feces of persons without urinary tract infections. Strains Ti and M12 are a wild-type urinary isolate and its urease-negative mutant, respectively, as described by MacLaren (10). All E. coli strains were urinary isolates.
doi:10.1128/iai.43.3.1068-1071.1984 fatcat:f6xyowae55epfbesbnv3rpqy6e