Microbial Mechanisms of Pathogenicity and Disease Epidemiology

Symbioses:
- Mutualism: Both partners benefit.
- Commensalism: One benefits, the other is unaffected.
- Antagonism: Both are harmed.
- Parasitism: One benefits, the other is harmed.
- Predation: One benefits, the other is killed.

Populations:
- Resident: Microbes that inhabit the host and typically do not cause harm, often in areas connected to the environment (e.g., GI and upper respiratory systems). They become familiar to the immune system over time.
- Transient: Microbes that are temporarily present.
Pathogens/Opportunists: Microbes that can cause disease under certain conditions.
Locations: Conjunctiva, nasal mucosa, oral mucosa, pharynx, skin, large intestine (colon), rectum, urethra, and vagina.

Resident microbiota inhabit the host without causing harm, typically in sites connected to the environment like the GI and upper respiratory systems.
The human body offers diverse habitats in terms of temperature, pH, nutrients, oxygen, and moisture, supporting a wide range of microbes.
Over time, resident microbes become familiar to the immune system.
Exposure to microbes and other organisms during critical developmental stages is important for immunoregulation.
Reduced exposure to these