DEFINED MUTANTS OF PROTEUS-MIRABILIS LACKING FLAGELLA CAUSE ASCENDINGURINARY-TRACT INFECTION IN MICE

A clinical isolate of Proteus mirabilis (Pr 990) and an isogenic non-f lagellate allelic replacement mutant (Pr M9) were tested for their abi lity to cause infection in the ascending mouse model of urinary tract infection. Wild-type Pr 990 differentiates into swarmer cells in brain -heart infusion broth. Pr Mg neither has flagella nor does it apparent ly differentiate into swarmer cells after subculturing. The infectivit y of both strains from an initial culture and the sixth subculture was assessed in the ascending urinary tract infection mouse model. infect ion was ascertained by determining colony forming units from kidney an d bladder homogenates from individual mice 7 days after inoculation. I n all cases the non-flagellate mutant Pr M9 was at least as infective as Pr 990. Using bacteria from the first culture, Pr M9 infected 61.5% and Pr 990 infected 45.5% of mice tested. The levels of viable counts were similar between the Pr Mg and the Pr 990 infections. Using bacte ria from the sixth subculture, Pr M9 infected 75% and Pr 990 infected 76.5% of mice tested. Again viable counts were similar. Pr 990 increas ed in infectivity from the first to the sixth subculture, whereas Pr M 9 did not, but this may be a reflection of the high initial rate of in fectivity with first culture Pr M9. These results suggest that neither flagella nor swarmer cells are required for P. mirabilis infectivity in ascending urinary tract infections in mice. (C) 1996 Academic Press Limited