Chapter 27-1

Question 1

Pathogens

Answer 1

Pathogens: microbe that causes disease.
Pathogenicity: ability of a microbe to cause disease.
Virulence: degree of pathogenically.
Opportunistic pathogen: causes disease only in absence of normal host resistance.

Question 2

Pathogens: Infections and Disease

Answer 2

Infection: Situation in which a microbe is established and growing in a host, whether or not the host is harmed.
Disease: Damage or injury to host that impairs host function.

Question 3

Host-microbe interactions

Answer 3

Animal bodies act as hosts and provide favorable environments:
-plentiful organic nutrients 
-available growth factors 
-appropriate pH, osmotic pressure and temp. 
Each body site is unique:
-skin: dry, high salt
-lung: oxygenated
-large intestine: anaerobic

Question 4

Frequent sites of infection

Answer 4

Infections frequently begin at mucous membranes:

-Mouth, pharynx, esophagus, urogenital tract, respiratory tract, GI tract.

Question 5

Mucous Membrane

Answer 5

Coated with mucus a viscous soluble glycoprotein.
Microorganisms associate loosely or firmly to them:
-Loosely associated swept away by physical means.
-Firmly attached may lead to a breach.

Question 6

“Normal microbiota”

Answer 6

Microbes that live on or within humans and are not pathogenic.
Commensals: organism that derives benefit from the host but does not harm the host.
mutualists:

Question 7

The skin microbiome

Answer 7

Skin is not uniform, pH, moisture availability, temp, UV exposure, O2/CO2.

• -“the desert of the forearm, the tropical forest of the armpit, the cool woods of the scalp”
• -Microbiome density: forehead (high), armpit, back, forearm (low).

Question 8

Antimicrobial skin defense mechanism

Answer 8

Keratin protein, acidic, sloughing of cells, frequent drying, salt, lysosymes (n-acetylmuramide glycanhydrolase).

Question 9

Sebum

Answer 9

skin pH averages 5.5 in adults and 7 in children due to sebum production and fermentation.
Propionbacterium sp.: aerotolerant actinobacteria that ferments sebum producing propionic acid.

Question 10

Variations in skin microbiome

Answer 10

Composition is influenced by:
-environmental factors (weather...). 
-host factors (age, hygiene...). 
Differs greatly between individuals.  
Can differ between hands.