Mechanisms of Pathogenicity Flashcards Preview

MB 351 - Exam 4 > Mechanisms of Pathogenicity > Flashcards

Flashcards in Mechanisms of Pathogenicity Deck (28):
1

Partnership of organisms of some sort

Symbiosis

2

One partner benefits, other is neutral

Commensalism

3

Both partners benefit

Mutualism

4

One partner benefits, other is harmed

Parasitism

5

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

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

6

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

1000

7

Dental Plaques (3)

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

8

Tooth decay occurs due to...

...lactic acid degradation by Streptococcus mutans and sobrinus

9

This bacteria causes ulcers in the stomach

Helicobacter pylori

10

Contributions of intestinal microorganisms (6)

-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)

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Disease

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

12

Pathogenicity

The ability of a microorganism to cause disease in a host

13

Virulence

The quantitative measure of pathogenicity

14

Virulence Factors

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

15

Virulence Factor Examples (4)

Fimbriae (adherence), proteases, hemolysins, toxins

16

The alteration of surface antigens

Antigenic Variation

17

Example of antigenic variation

Vibrio cholerae alters its O antigen (200+ serotypes)

18

Mechanisms of Pathogenicity (5)

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

19

Entry and Barriers to Entry

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

20

Numbers of Invading Microbes

-LD50: Lethal dose for 50% of animal test population
-High virulence = Low cell counts

21

Adherence

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

22

Penetration of Host Defenses (2)

-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)

23

Evasion of Host Defenses (3)

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

24

Toxin

Substance that contributes to pathogenicity

25

Damage to Host Cells

-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

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Endotoxins Denaturation and Pyrogenicity

-Denaturation: No
-Pyrogenicity: Yes

27

Exotoxin Denaturation and Pyrogenicity

-Denaturation: Usually
-Pyrogenicity: Occasionally

28

Pyrogenic Response to Endotoxins (4)

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