Bac/fungi Pathogenesis

Question 0

Facultative intracellular

Answer 0

Can reproduce within and outside of host cell

Salmonella, Neisseria, Brucella, Mycobacterium, Listeria Francisella, Legionella, Yersinia Petis

(see first aid pneumonic)

Question 1

Obligate Intracellular

Answer 1

Can’t make own ATP
Can’t reproduce outside of host cell

Rickettsia
Chlamydia

Question 2

STEPS OF THE PATHOGENIC CYCLE

Answer 2

Exposure & Entry 
Attachment 
Invasion 
Evasion of immune response
Effects on host 
Dissemination/Shedding

Question 3

Attachment

Answer 3

Requires host cell receptors & microbial surface components (Adhesins such as pili/fimbriae, LPS, Lipoteichoic Acid, Mannans)

Question 4

Invasion

Answer 4

Ex: Phagocytosis, endocytosis, cytoskeleton rearrangement (membrane ruffling)

Question 5

Evasion of immune response

Answer 5

Ex)
Compliment evasion = capsules, host cell mimicry, compliment binding proteins, proteases (elastase, C5a peptidase)

Phagocyte evasion = capsules, intracellular parasitism
Antibody evasion = Ig binding/inactivating, antigenic variation

Question 6

Leukocidins

Answer 6

Kills neutrophils and macrophages

Alters phospholipid metabolism by ADP-ribosylation of a protein controlling phosphatidylinositol = disruption of cellular activities

Question 7

Biofilms

Answer 7

Collection of microorganisms that are attached to a surface, covered by a microbially-produced exopolymeric substance (EPS)

Bacteria growing as biofilms can be SIGNIFICANTLY more resistant to antimicrobial agents

Question 8

Effect on Host

Answer 8

1. Degradative Enzymes (kinases) result in spreading to other tissues
2. Physical growth through tissues: Fungal growth
3. Toxic Structures: Lipid A/LPS/Endotoxin
4. Toxins: exotoxins (-ve), aflatoxin (fungi, carcinogenic), Gliotoxin (fungi, induces apoptosis)

Question 9

Classes of Exotoxins

Answer 9

Class I: membrane binding/acting
Class II: membrane damaging
Class III: Interacellular

Question 10

Superantigens

Answer 10

cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release (INF-gamma, IL-2)
Ex: toxic shock syndrome (staph), Rheumatic fever (strep)

Question 11

Dissemination

Answer 11

a) Direct: In surface fluids
- Facilitated by toxin production (Ex: hyaluronidase, etc.)
- Growth through tissues, (fungi)
b) Cross blood-CSF junction (choroid plexus)
c) Blood or blood components
d) Lymphatics/ immune system cells