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Published on: February 22, 2017
Interaction of Rickettsia prowazekii strains of different virulence with white rat macrophages
G A Penkina1, V F Ignatovich, N M Balayeva
1Gamaleya Research Institute of Epidemiology and Microbiology, Moscow, Russia.
Abstract:
The growth of mildly pathogenic strain E, its virulent revertant EVir, and prototype virulent strain Breinl of Rickettsia prowazekii in peritoneal macrophage cultures of outbread white rats (WR) was evaluated by light microscopy and bioassay in chick embryos (CE). Macrophage cultures infected with strain E were characteristic by limited number of infected cells, poor or moderate accumulation of rickettsiae in individual cells, poor or nil spread of infectious process during first 7 days of infection, and the death of rickettsiae in cultures as determined by the bioassay in CE. Moreover, rickettsiae were not determined in 20.7% of infected macrophage cultures by either microscopic or bioassay methods. In contrast, the growth of virulent strains EVir and Breinl was characteristic by higher proportion of infected cells, considerable accumulation of rickettsiae, and intensive spread of infectious process within 5-7 days post infection (p.i.). However, the intensity of infectious process in macrophage cultures was less expressed with strain EVir than with strain Breinl.
Insights
Mildly pathogenic Rickettsia prowazekii strain E showed limited growth in rat macrophage cultures, unlike virulent strains EVir and Breinl. Virulent strains demonstrated more extensive infection and rickettsiae accumulation.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Rickettsia prowazekii causes epidemic typhus.
- Understanding the in vitro growth patterns of different strains is crucial for disease research.
Purpose of the Study:
- To compare the in vitro growth and replication of a mildly pathogenic Rickettsia prowazekii strain (E) with its virulent revertant (EVir) and a prototype virulent strain (Breinl) in rat macrophage cultures.
Main Methods:
- Peritoneal macrophage cultures from outbred white rats (WR) were infected with Rickettsia prowazekii strains E, EVir, and Breinl.
- Infection was evaluated using light microscopy and bioassays in chick embryos (CE).
Main Results:
- Strain E exhibited limited infected cells, poor rickettsiae accumulation, and minimal spread, with some cultures showing no viable rickettsiae.
- Virulent strains EVir and Breinl showed higher infection rates, greater rickettsiae accumulation, and intensive spread within 5-7 days post-infection.
- Strain Breinl demonstrated a more intense infectious process compared to strain EVir.
Conclusions:
- Virulent strains of Rickettsia prowazekii replicate more effectively in rat macrophages than mildly pathogenic strains.
- Macrophage cultures provide a valuable model for studying Rickettsia prowazekii pathogenesis and strain differences.
