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Defined mutants of Proteus mirabilis lacking flagella cause ascending urinary tract infection in mice
C Legnani-Fajardo1, P Zunino, C Piccini
1Division of Microbiologia, Instituto de investigaciones Biologicas Clemente Estable, Montevideo, Uruguay.
Abstract:
A clinical isolate of Proteus mirabilis (Pr 990) and an isogenic non-flagellate allelic replacement mutant (Pr M9) were tested for their ability 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 M9 neither has flagella nor does it apparently differentiate into swarmer cells after subculturing. The infectivity of both strains from an initial culture and the sixth subculture was assessed in the ascending urinary tract infection mouse model. Infection was ascertained by determining colony forming units from kidney and bladder homogenates from individual mice 7 days after inoculation. In all cases the nonflagellate 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 M9 and the Pr 990 infections. Using bacteria from the sixth subculture, Pr M9 infected 75% and Pr 990 infected 76.5% of mice tested. Again viable counts were similar. Pr 990 increased in infectivity from the first to the sixth subculture, whereas Pr M9 did not, but this may be a reflection of the high initial rate of infectivity 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.
Insights
Flagella and swarmer cells are not essential for Proteus mirabilis to cause urinary tract infections in mice. A non-flagellate mutant showed similar infectivity to the wild-type strain in a mouse model.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Proteus mirabilis is a common cause of urinary tract infections (UTIs).
- Flagella and swarming motility are considered important virulence factors for P. mirabilis.
- The role of these factors in ascending UTIs requires further investigation.
Purpose of the Study:
- To investigate the necessity of flagella and swarmer cell differentiation for P. mirabilis infectivity in a mouse model of ascending UTI.
Main Methods:
- A clinical isolate of P. mirabilis (Pr 990) and its non-flagellate mutant (Pr M9) were used.
- Infectivity was assessed using an ascending mouse model of UTI.
- Bacterial load was quantified by colony-forming units in kidney and bladder homogenates.
Main Results:
- The non-flagellate mutant Pr M9 demonstrated comparable or even higher infectivity than the wild-type Pr 990.
- Both strains showed similar viable bacterial counts in infected organs.
- Wild-type P. mirabilis showed increased infectivity after subculturing, while the mutant did not.
Conclusions:
- Flagella and swarmer cell differentiation are not required for P. mirabilis to establish ascending urinary tract infections in mice.
- Other virulence factors likely play a significant role in P. mirabilis pathogenesis.