Opportunistic Pathogen

∞ generated and posted on 2016.03.03 ∞

Microorganism that normally does not cause disease but nevertheless can cause disease under certain relatively unusual circumstances.

Opportunistic Pathogens usually are bacteria though include some fungi as well. They usually exist as benign members of normal flora in or on a body, but under certain circumstances nonetheless are capable of causing disease.

Opportunistic pathogens often are otherwise members of an normal flora, though can also be relatively common environmental organisms. Somewhat consistently, disease is a consequence of organisms finding their way to not-typical locations in the body, such as caused by , or due to or otherwise of hosts, e.g., .

An opportunistic pathogen basically needs to be in the right place at the right time to cause disease but normally these circumstances do not coincide and the organism, consequently is otherwise harmless. See also opportunistic infections.

As a , however (from ):

…an opportunistic microorganism has been defined as "one that utilizes the opportunity offered by weakened defense mechanisms to inflict damage to the host" but does not exclude for a normal host when a large or specific virulence factors can overcome . This definition was so broad that, depending on the clinical situation, it could also include Streptococcus , S. , and , which also cause disease in normal individuals . In this regard, it has been noted that if invasion and disease require a breakdown in normal defenses, then all can actually be considered opportunistic . These definitions illustrate that although the concept of opportunism has been extremely important for our understanding of the host-microbe relationship in the setting of , the term opportunistic does not convey a universal meaning…

Which is not to say that the concept of "" should be abandoned but instead that the term is not necessarily always used consistently.