Proteus mirabilis fimbriae: construction of an isogenic pmfA mutant and analysis of virulence in a CBA mouse model of ascending urinary tract infection.

Proteus mirabilis, a cause of urinary tract infection and acute pyelonephritis, produces a number of different fimbriae. An isogenic fimbrial mutant of P. mirabilis HI4320 was constructed by marker exchange with delta pmfA::aphA to determine the role of the P. mirabilis fimbriae (PMF) in hemagglutination and in virulence in the CBA mouse model of ascending urinary tract infection. The pmfA mutant, which did not express the 19,500-Da major subunit of PMF, colonized the bladders of transurethrally challenged CBA mice (n = 20 in each group) in numbers 83-fold lower than those of the wild-type strain (mutant, log10 4.87 CFU/g; wild-type strain, log10 6.79 CFU/g; P = 0.023). However, the mutant colonized the kidneys in numbers similar to those of the wild-type strain. Hemagglutination patterns of the mutant ruled out the involvement of PMF in both mannose-resistant, Proteus-like and mannose-resistant, Klebsiella-like hemagglutination. Similarly, PMF does not appear to be involved in adherence to uroepithelial cells (UEC), since the mutant was as adherent as the wild-type strain (mutant, 14.1 +/- 11.7 mean bacteria per UEC, 60% of UEC with > or = 10 bacteria; wild-type strain, 18.1 +/- 16.2 mean bacteria per UEC, 68% of UEC with > or = 10 bacteria; not significantly different). These data suggest a role for PMF in colonization of the bladder but not in colonization of kidney tissue. PMF appear not to be responsible for mannose-resistant, Proteus-like or mannose-resistant, Klebsiella-like hemagglutination.