I never really understood the difference between intracellular and extracellular pathogens. I considered all pathogens to be intracellular and disseminate and infect from within the host cell. The book differentiates the two as one being accessible to the soluble and secreted molecules of the immune system where as the other does not (Lodish). This is true but there are other characteristics that distinguish the two. Extracellular pathogens proliferate at sites such as mucousal surfaces, vascular, lymphatic, and body cavity fluids. They have been seen to have a phase of intracellular residence that is crucial to their extracellular infection where fatal factors carry out the pathology of the disease (Silva). Intracellular pathogens utilize a range of host cells such as macrophages and endothelial cells but before this occurs, they exist in the extracellular space. In order for the infection to spread, the pathogen must travel from one host cell to the next. Not all go through this phase but the majority do (Silva). Some have been seen to have extracellular activity aside from “cell-hopping” that increases their chances of pathogenicity and in some cases may be the cause for the severity of the disease and even the “terminal infectious episiode preceding the death of the infected host.”
The lifestyle pathogens portray in contaminated hosts is vital to their characterization. The purpose of this paper was centered around just that. How in order to properly and accurately label pathogens is to observe its behavior in the host cell, in-vivo to support the “dual intracellular/ extracellular lifestyles” of pathogens (Silva).
Question: Do you think that intracellular pathogens have a higher success rate of infection compared to extracellular knowing that intracellular pathogens enter the host and have extracellular activity where as extracellular pathogens work from the outside along side with virulent factors? What do y’all think?
Silva, Manuel T. “Classical Labeling of Bacterial Pathogens According to Their Lifestyle in the Host: Inconsistencies and Alternatives.” Frontiers in Microbiology 3 (2012): 71. PMC. Web. 23 Jan. 2018.
Lodish, Harvey F. Molecular Cell Biology. W.H. Freeman and Company, 2016.