Chapter 24, 25, 26, 27, 30 (Selected topics - Microbe-Human Interactions)

Where are normal microbiota found?

Skin, mouth, gastrointestinal tract, respiratory tract, urogenital tract

What are the roles of normal microbiota in maintaining health?

• Colonization resistance (prevent pathogens)

• Produce vitamins, amino acids, organic acids

• Help develop immune system

What are the characteristics/conditions of the skin?

Dry, salty, acidic, low moisture → inhospitable environment

What is an example of bacteria on skin?

Propionibacterium acnes or Cutibacterium acnes

What are the conditions of the mouth?

Moist, saliva present, near neutral pH

what is an example bacteria in the mouth?

Streptococcus spp.

What is dental plaque?

Biofilm of bacteria on teeth

What are the conditions of the stomach?

Very acidic (pH ~2), kills most microbes

Example bacteria in stomach?

Helicobacter pylori

What are the conditions of the small intestine?

Bile, enzymes, movement → fewer microbes

What are the conditions of the large intestine?

Anaerobic, nutrient-rich → MOST microbial growth

Example bacteria in large intestine?

Bacteroides, Clostridium

What are the conditions of the respiratory tract?

Mucus, cilia, lysozyme remove microbes

Example bacteria in upper respiratory tract?

Staphylococci, streptococci

What is unique about lower respiratory tract?

No normal microbiota (sterile)

Conditions of urogenital tract?

Vag is acidic

Example bacteria?

Lactobacillus acidophilus

What is infection?

Microbe enters and multiplies

What is disease?

Damage or symptoms occur

How can normal microbiota cause disease?

Become opportunistic when:

• In wrong location

• Immune system weakened

• Overgrowth

What are the stages of infectious disease?

Incubation → prodromal → illness → decline → convalescence

What factors influence disease outcome?

Virulence, host immunity, dose/exposure

What is a reservoir?

Natural habitat of pathogen

What is a vector?

Living organism that transmits disease

What is a fomite?

Contaminated object

Direct transmission?

Person-to-person

Indirect transmission?

Through objects, food, water, or vectors

What is a common-source outbreak?

Rapid spike, same source

What is a propagated outbreak?

Slow spread person-to-person

What is the function of the immune system?

Recognize and destroy pathogens

Characteristics of innate immunity?

Fast, nonspecific, no memory

Innate barriers to pathogen invasion?

Skin, mucus, cilia, lysozyme

Innate immune cells?

Phagocytes (macrophages, neutrophils), NK cells

Characteristics of adaptive immunity?

Specific, slower, has memory

Adaptive immune cells?

B cells (antibodies), T cells

Cell-mediated immunity?

T cells kill infected cells

Antibody-mediated immunity?

B cells produce antibodies

Active immunity?

Body produces antibodies

Passive immunity?

Antibodies received

Natural active immunity?

Infection

Artificial active immunity?

Vaccination

Natural passive immunity?

Mother → baby (materinal antibody)

Artificial passive immunity?

Immune globulin therapy