An infection is the
detrimental colonization of a host organism by a foreign species. The
colonizing organism interferes with the normal functioning and perhaps
the survival of the host. The infecting organism is referred to as a
pathogen, which may be bacterial, a parasite, fungal, or a virus, prion
or viroid. The scientific study of diseases in medicine caused by
biological agents is infectious diseases.
All multicellular organisms are colonized to some degree by extrinsic
organisms, and the vast majority of these exist in either a symbiotic,
commensal, or parasitic relationship with the host. An example of the
former would be the anaerobic bacteria species which colonize the
mammalian colon, an example of the latter would be the various species
of staphylococcus which exist on human skin. Neither of these
colonizations would be considered infections.
An infection is, in effect, a war in which the infecting organism seeks
to utilize the host resources in order to multiply at the expense of
The difference between an infection and a colonization is often only a
matter of circumstance. Organisms which are normally non-pathogenic can
become pathogenic under the right conditions, and even the most
virulent organism requires certain circumstances to cause a
The variables involved in the outcome of a host becoming inoculated by
a pathogen and the ultimate outcome include:
* the route of entry of the pathogen and the access
to host regions that it gains
As an example, the
staphylococcus species present on skin remain harmless on the skin, but
when present in a normally sterile space, such as in the capsule of a
joint, or the peritoneum, will multiply without resistance and create a
burden on the host.
- the intrinsic virulence of the particular
- the quantity or load of the initial
- the immune status of the host being
type of food borne illness occur when the food
eaten is contaminated with living pathogenic bacteria.
type of bacteria will determine the time for symptoms to appear. The
bacteria will pass through your stomach and down into your lover
intestine. It will embed themselves in the wall of the intestine and it
infection most often cause diarrhea (sometimes
bloody), stomach cramps and fever. More...