General
characters
·
They are small Gram negative bacilli adapted to obligate
intracellular parasitism, transmitted by arthropod vectors. They are
primary parasites of arthropods such as lice, fleas, ticks, in which they are
found in the alimentary canal. In vertebrates they infect vascular endothelium,
reticuloendothelial cells.
·
This pleomorphic coccobacilli are nonmotile,
noncapsulated. They stain bluish purple with Giemsa stain. It has a 3 layered
cell wal , a trilaminar plasma membrane
and an outer slime layer.
·
Growth occurs in the cytoplasm of infected
cells, nucleus etc. the optimum temperature is 32-350C. they are
readily cultivated in the yolksac of chick embryos, HeLa cells etc., in
arthropods.
·
They multiply by binary fission.
·
They are inactivated by physical and chemical
agents. They are rapidly destroyed at room temperature when seperated from host
components, susceptible to tetracycline, chloramphenicol, ciprofloxacin,
lysozyme. Sulfonamides enhance the growth and worsen the condition of patients.
·
They possess both RNA and DNA.
·
They are large enough to be seen under the light
microscope and are held back by bacterial filters.
