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Growth, cellular differentiation and virulence factor expression by Proteus mirabilis in vitro and in vivo
P Zunino1, C Piccini1, C Legnani-Fajardo1
1Division Microbiologia, Instituto de Investigaciones Biologicas Clemente Estable, Avda. Italia 3318, CP11600, Montevideo, Uruguay.
Abstract:
A uropathogenic strain of Proteus mirabilis was grown in vitro in human and mouse urine and brain-heart infusion broth (BHIB) and in vivo in subcutaneous open chambers (SOC) in mice, intraperitoneal diffusion chambers (IPC) in rats and by ascending urinary tract infection in mice in order to compare growth pattern, cellular differentiation and expression of virulence factors. Although the growth rate was slower in vivo than in vitro, the extent of growth was similar after 24 h. PR mirabilis differentiated into filamentous swarmer cells in all in-vitro culture conditions, but no filamentous cells were observed in either of the in-vivo chamber models. Transurethrally infected mice showed a rapid release or loss of filamentous cells and these could not be seen in kidney or bladder homogenates 7 days after infection. Bacteria showed increasing haemagglutination titres for fresh and tanned red blood cells after subculturing in BHIB, but bacteria grown in vivo did not show haemagglutination. An increasing resistance to normal serum was found when bacteria were grown in vivo. Significant haemolytic activity was detected with bacteria grown in BHIB and IPC, but almost no activity was found when bacteria had grown in urine. These findings improve the understanding of the role of P. mirabilis uropathogenic virulence factors in vivo.
Insights
Proteus mirabilis exhibits distinct growth and virulence factor expression in vitro versus in vivo. Uropathogenic bacteria lose filamentous swarmer cells and haemagglutination in vivo, gaining serum resistance.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Uropathogenic Proteus mirabilis causes urinary tract infections.
- Understanding virulence factor expression in vivo is crucial for infection control.
Purpose of the Study:
- To compare the in vitro and in vivo growth patterns, cellular differentiation, and virulence factor expression of Proteus mirabilis.
- To elucidate the role of P. mirabilis virulence factors during infection.
Main Methods:
- In vitro culture in human/mouse urine and brain-heart infusion broth (BHIB).
- In vivo models: subcutaneous open chambers (SOC) in mice, intraperitoneal diffusion chambers (IPC) in rats, and ascending urinary tract infection in mice.
- Assessment of growth, cellular differentiation, haemagglutination, haemolytic activity, and serum resistance.
Main Results:
- In vivo growth was slower but reached similar levels as in vitro after 24 hours.
- Proteus mirabilis differentiated into filamentous swarmer cells in vitro but not in vivo chamber models.
- Filamentous cells were lost rapidly in transurethrally infected mice.
- Haemagglutination titres increased with BHIB subculturing but were absent in vivo.
- In vivo growth increased resistance to normal serum.
- Haemolytic activity was high in BHIB and IPC but low in urine.
Conclusions:
- Proteus mirabilis exhibits significant phenotypic changes between in vitro and in vivo environments.
- Virulence factor expression, including filamentous swarmer cell formation and haemagglutination, is suppressed in vivo.
- Increased serum resistance in vivo suggests adaptation to the host environment.