Bacteria (including mycoplasma), yeast, and protozoans which inhabit the skin and mucosa of healthy persons 10^13 cells; 10^14 bacteria
What are three characteristics of normal flora:
1. Resident -- what you expect 2. Transient -- edging towards pathogenic, high turnover rate (e.g. S aureus) 3. Usually commensal -- (you are food and shelter !)
Normal Flora are non-pathogenic - True or False?
False NF does not mean non-pathogeic
80% of the dry weight of the GI tracts = Normal Flora - True or False?
Concept that bacteria go where they compete and stick best:
Bacteria are not essential to life- True or False?
True -- germ free animals do fine
Why is it that highly invasive bacteria causes diarrhea in adults but not in newborns?
This exhibits the idea that specificity of receptors on cells changes with age --- newborns have yet to develop the associated receptor
What is bacterial interference?
1. Bacteria compete for binding sites 2. Compete for nutrients 3. Elaborate antibacterial factors vs. pathogens
NF compete with pathogenic bacteria
What benefit do NF provide?
1. Metabolism in the GI tract (b/d nutrients for absoprtion) 2. Stiulation of GI and other mucosal immune sites, cells, systems (i.e. priming of innate and adaptive immunity) 3. Development of cross reactive, protective antibodies on surface of bacteria
Loss of normal flora often leads to what?
1. Sites for pathogen adherence 2. Absence of interference allows replication after adherence 3. Skin, respiratory, GI and GU mucoae all are susceptible to adverse effect
INCREASED SUSCEPTIBILITY TO INVASION BY PATHOGENS
How can normal flora be potential pathogens?
If they penetrate the mucosa that they are living in --- can change the local environment -- causing disease
EX: adherence to perineal and vaginal surface --> UTI Skin trauma introduces bacteria -- especially transient NF such as S. aureus -- to new adherence sites.
What are the 4 determinants of NF?
1. Age 2. Menstrual status 3. Environment (temperature, humidity) 4. Diet/nutritional state
What NF is common to the nose (skin and mucosa)?
1. Corynebacterium spp 2. S. epidermidis (resident) 3. S. aureus (transient) 4. Streptococci
What NF is common to the oral mucosa?
1. alpha hemolytic streptococci 2. gram negative anaerobic bacilli, facultative cocci, actinomycetes (dental plaques), protozoans, and candida (fungus) **** more likely to cause problem
Pneumonia (inflammation of the lungs) or lung abscess (destruction of tissue and replacement by white blood cells
How can you mess up the NF?
Antibiotics -- decrease bacterial interference allowing: 1. Attachment of pathogens (respiratory mucosa, skin) 2. Replication of pathogens (GI) 3. Loss of protective pH (vagina) 4. Increased susceptibility to enteric pathogens like salmonella, etc. 5. The clostridium difficult problem (lose colon's function to absorb water)