Mechanisms of Pathogenicity

Question 1

Partnership of organisms of some sort

Answer 1

Symbiosis

Question 2

One partner benefits, other is neutral

Answer 2

Commensalism

Question 3

Both partners benefit

Answer 3

Mutualism

Question 4

One partner benefits, other is harmed

Answer 4

Parasitism

Question 5

Bacteria are found on these parts of the body (5)

Answer 5

GI Tract, Mouth, Urogenital Tract, Skin, Respiratory Tract

Question 6

There are more than ____ species of bacteria in the body’s natural flora

Answer 6

1000

Question 7

Dental Plaques (3)

Answer 7

• Obligate anaerobes
• Mixed culture biofilms made of thick layer
• Variety of bacteria, proteins, and water protects against lysozyme that degrades peptidoglycan cell walls

Question 8

Tooth decay occurs due to…

Answer 8

…lactic acid degradation by Streptococcus mutans and sobrinus

Question 9

This bacteria causes ulcers in the stomach

Answer 9

Helicobacter pylori

Question 10

Contributions of intestinal microorganisms (6)

Answer 10

• Vitamin synthesis (e.g. Thiamine, Riboflavin, B12, K)
• Gas Production (CO2, CH4, H2)
• Odor Production (H2S, NH3, amines, indole)
• Organic Acid Production (Acetic, Propanoic, Butanoic)
• Glycosidase Reactions
• Steroid Metabolism (Bile Acids)

Question 11

Disease

Answer 11

Impairment of the normal state of an organism or any component that hinders function

Question 12

Pathogenicity

Answer 12

The ability of a microorganism to cause disease in a host

Question 13

Virulence

Answer 13

The quantitative measure of pathogenicity

Question 14

Virulence Factors

Answer 14

Microbial components (structural or extracellular) that aid in the establishment, spread, and maintenance of disease

Question 15

Virulence Factor Examples (4)

Answer 15

Fimbriae (adherence), proteases, hemolysins, toxins

Question 16

The alteration of surface antigens

Answer 16

Antigenic Variation

Question 17

Example of antigenic variation

Answer 17

Vibrio cholerae alters its O antigen (200+ serotypes)

Question 18

Mechanisms of Pathogenicity (5)

Answer 18

1. Portals of Entry
2. Number of Microbes
3. Adherence
4. Penetration or Evasion of Host Defenses
5. Damage to Host Cells/Cytopathic Effects

Question 19

Entry and Barriers to Entry

Answer 19

• Invasion: Most pathogens must penetrate the epithelium to cause disease
• Entry: Mucous membranes (respiratory, GI), Skin, Parenteral Route (Needle)
• Barriers: Acidity, Physical barrier, Mucus

Question 20

Numbers of Invading Microbes

Answer 20

• LD50: Lethal dose for 50% of animal test population

- High virulence = Low cell counts

Question 21

Adherence

Answer 21

• Adhesins/ligands bind to receptors on host cells (e.g. glycocalyx)
• Form biofilms
• E.g. Glycocalyx helps Streptococcus mutans bind to tooth surface

Question 22

Penetration of Host Defenses (2)

Answer 22

• Enzymes (e.g. Hemolysins lyse RBCs to get iron)

- Invasion proteins (e.g. Salmonella alters actin to ruffle cell membrane to become engulfed and gain entry)

Question 23

Evasion of Host Defenses (3)

Answer 23

• Capsules prevent phagocytosis (e.g. Bacillus anthracis)
• Cell wall components (e.g. Mycolic acid in Mycobacterium tuberculosis helps resist digestion)
• Antigenic Variation

Question 24

Toxin

Answer 24

Substance that contributes to pathogenicity

Question 25

Damage to Host Cells

Answer 25

- Exotoxins: extracellular protein with high potency and specificity (e.g. cholera enterotoxin [affects small intestine] induces diarrhea) - Endotoxin: outer membrane LPS with low potency and specificity

Question 26

Endotoxins Denaturation and Pyrogenicity

Answer 26

- Denaturation: No | - Pyrogenicity: Yes

Question 27

Exotoxin Denaturation and Pyrogenicity

Answer 27

- Denaturation: Usually | - Pyrogenicity: Occasionally

Question 28

Pyrogenic Response to Endotoxins (4)

Answer 28

1. Macrophage ingests gram-negative bacterium (e.g. E. coli) 2. Bacterium is degraded in vacuole, releasing endotoxins that prompt the macrophage to produce IL-1 and TNF-alpha 3. Cytokines are released into bloodstream 4. Cytokines induce hypothalamus to produce prostaglandins to raise body temperature