Schaechters: Chapter 2 Normal Microbiota

%%Normal microbiota%%: microorganisms frequently found on or in the body of healthy persons
* however, no microorganism is intrinsically benign or pathogenic
* depend on location of microorganisms( on lumen or in deep tissue) and host ability to maintain homeostasis
Parts of the body that contain large amounts of Microorgnism
  * Skin: moist areas epically, such as the group and between the toes
  * Respiratory tract: nose or oropharynx
  * digestive tract: mouth and large intestine
  * urinary tract: anterior part of the urethra
  * Genital system: vagina
Body Sites that are usually sterile
  * blood
  * cerebrospinal fluid
  * synovial fluid
  * deep tissues in general

Microorganisms have to resist host mechanisms and successfully compete against other microbial species!
commensal bacterica( aka symbiotic bacteria) have the advantage of previous occupancy
* some microbes however stimulate an inflammatory response that they can withstand and diminishes normal microbiota

%%Tissue Tropism%%: reflects the ability of a given pathogen to infect a specific organ or sets of organs
* determined by tissue-specific cellular properties, like specific receptors on the surface of certain cells, or physical properties like temperature or pH
* for example, Influenza virus depends on special glycoproteins only found on the surface of respiratory epithelial cells. Therefore Influzn is only found in the respiratory system.

A common source of Infection
Immune Stimulation
Keeping out invaders
metabolizing nutrition
* %%microbiome%%: a complex collection of genomes present in gut with coding capacity for many more metabolic pathways than our own genomes have

Traditionally raising animals in sterile conditions → germe-free animals
  * can be done with rodents who were born via a cesarian and chickens with disinfected shells before hatching
  * under germ fee conditions, rodents thrive when given vitamin supplements in diets
    * faster growth