Extracellular Bacterial Infections

Extracellular bacteria are bacteria that can replicate outside of the cell, in circulation, the extracellular connective tissue, and in various tissues. Various types of bacteria including bacterial extracellular group mentioned in the previous chapter. Extracellular bacteria are usually easily destroyed by phagocytic cells. In certain circumstances extracellular bacteria can not be destroyed by phagocytic cells because of the capsule synthesis antifagosit, namely outer capsule (outer capsule) which resulted in a bad adhesion between phagocytic cells with bacteria, such as bacterial infection of Streptococcus pneumoniae capsule or Haemophylus influenzae.


In addition, the capsule is to protect the carbohydrate molecules on the surface of bacteria that would otherwise be recognized by receptors of phagocytes. With the capsule, the access of phagocytes and deposition of C3b on the bacterial cell wall can be inhibited. Several other organisms that release toxic exotoxin leukocytes. Another strategy is the binding of bacteria to the surface of non-phagocytic cells so as to obtain the protection of phagocyte function.

Normal cells in the body has a regulatory protein that protects from damage by complement, such as CR1, MCP and DAF, which led to solving C3 convertases. Some bacteria do not have a regulator, so that will activate the alternative pathway of complement through the stabilization C3b3b convertases on the bacterial cell surface. With the capsule of bacteria will cause complement activation and stabilization of the poor.

Some bacteria also can accelerate the solving of complement through the action of microbial products that bind or inhibit the work of regulators of complement activation. Even some species to avoid lysis by altering the location of the complement activation through the secretion of protein bait (decoy protein) or bacterial surface position away from the cell membrane. Some Gram-positive organisms have a thick peptidoglycan layer that prevents insertion of membrane attack complex C5b-9 on the bacterial cell membrane.

Enteric Gram-negative bacteria in the gut affects the activity of macrophages, including inducing apoptosis, increased production of IL-1, preventing fusion fagosom sitoskleton-lysosomes and affects actin. The strategy of antigenic variation is also owned by some bacteria, such as variations in lipoprotein surface, variations in enzymes involved in the synthesis of surface structures and antigenic variation pili.Keadaan immune system which can cause extracellular bacteria are difficult to destroy because of interference with the mechanism of phagocytic deficiency phagocytic cells (neutropenia) or quality of immune responses that are less (chronic granulomatous disease).