Phylogenetic analysis also revealed that many strains or lineages of Salmonella exist, which is advantageous for the pathogen because its genetic diversity can acts as fodder for natural selection to tinder with.
For instance, Clostridioides difficile is the most frequent cause of nosocomial diarrhea worldwide, and reports in the early 2000s indicated the advent of a hypervirulent strain in North America and Europe.
The authors saw that hypervirulent strains had undergone various types of niche adaptation like antibiotic resistance, motility, adhesion, and enteric metabolism.
They are not harmful to the body when the body's immune system is functioning normally, but if the host immune system becomes compromised, or loses its ability to function at its full or near-full potential, opportunistic pathogens switch from being a commensal organism to a pathogen.
Candida albicans is a type of fungus/yeast found in the intestines and mucous membranes (like the vagina and throat) of healthy humans.
In healthy humans- meaning humans with functioning immune systems- Candida will not cause infections.
However, if a person receives chemotherapy or has HIV/AIDS, which weakens the immune system (thus compromising it), Candida albicans will cause infections.
Other adaptations of the commensal pathogen include the ability to grow at host temperature, create biofilms, resist reactive oxygen species (ROS) created as part of the human immune response to fight off infection, adapt to different pHs [8] (relevant for being carried in the blood in different parts of the body) and adapt to low nutrient or low glucose environments like the liver [9] Because Candida albicans is very good at adapting to the fluctuating environments of the humans body (i.e. its changing temperature, pH, oxygen reactivity and more) candida albicans is a good pathogen.
For instance, the innate and acquired immune responses are adaptations of the human body that exist for the sole purpose of warding off disease.
Additionally, as was previously mentioned with the case of reactive oxygen species, the body has various other ways off warding off threats.