Exit from host cell
The cytosol of the host cell contains nutrients, adenosine triphosphate, amino acids, and nucleotides which are used by the bacteria for growth. For this reason, as well as to avoid phagolysosomal fusion and death, rickettsiae must escape from the phagosome. To escape from the phagosome, the bacteria secrete phospholipase D and hemolysin C. This causes disruption of the phagosomal membrane and allows the bacteria to escape. Following generation time in the cytoplasm of the host cells, the bacteria utilizes actin based motility to move through the cytosol.RickA, expressed on the rickettsial surface, activates Arp2/3 and causes actin polymerization. The rickettsiae use the actin to propel themselves throughout the cytosol to the surface of the host cell. This causes the host cell membrane to protrude outward and invaginate the membrane of an adjacent cell. The bacteria are then taken up by the neighboring cell in a double membrane vacuole that the bacteria can subsequently lyse, enabling spread from cell to cell without exposure to the extracellular environment. Consequences of infection
Rickettsia rickettsii initially infect blood vessel endothelial cells, but eventually migrate to vital organs such as the brain, skin, and the heart via the blood stream. Bacterial replication in host cells causes endothelial cell proliferation and inflammation, resulting in mononuclear cell infiltration into blood vessels and subsequent red blood cell leakage into surrounding tissues. The characteristic rash observed in Rocky Mountain spotted fever is the direct result of this localized replication of rickettsia in blood vessel endothelial cells.
Nevus spilus, also known as speckled lentiginous nevus, is a light brown or tan birth mark, speckled with small, dark spots or small bumps. If it occurs in a segmental pattern then it is sometimes referred to as a Zosteriform speckled lentiginous nevus.It may be associated with types of phakomatosis pigmentovascularis.Prevalence is between 0.2% and 2.8%. See also
Phakomatosis pigmentokeratotica
Skin lesion
List of cutaneous conditions

References


== External links ==