Microbial Pathogenesis

Question 1

Pathogen

Answer 1

microbial agent of disease; causes disease by hiding from immune system or using virulence factors to escape/resist

Question 2

Ectoparasite

Answer 2

lives on surface of host (ex. mosquito)

Question 3

Endoparasite

Answer 3

lives inside the body of host

Question 4

Infection

Answer 4

occurs when a pathogen or parasite enters or begins to grow on a host, is measured by infectious dose (ID)

Question 5

Pathogenicity

Answer 5

the organism’s ability to cause disease

Question 6

Infectivity

Answer 6

how easily an organism can spread and cause disease

Question 7

Virulence

Answer 7

measure of disease severity, measured via the infectious dose (ID) and/or the lethal dose (LD)

Question 8

LD50

Answer 8

the dosage of microbes that will kill half of the infected hosts

Question 9

Lower LD indicates __________

Answer 9

higher virulence

Question 10

Primary pathogens

Answer 10

cause disease in healthy host

Question 11

Opportunistic pathogens

Answer 11

causes disease in immunocompromised hosts

Question 12

Pathogenicity Islands

Answer 12

where virulence genes are found in chromosomes, plasmids, or phage genomes (contains a cluster of virulence genes)

Question 13

Carlos J. Finlay

Answer 13

first to identify Aedes aegypti as a vector of yellow fever

Question 14

Walter Reed

Answer 14

confirmed in 1901 that the mosquito Aedes aegypti is the vector of transmission for yellow fever

Question 15

To cause disease, all pathogens must….

Answer 15

• Enter a host
• Find their unique niche
• Avoid, circumvent, or subvert normal host defenses
• Multiply
• Transit to a new susceptible host

Question 16

Type 1 pili adhesion

Answer 16

static attachment to host cell via mannose residues; grow from outer membrane

Question 17

Type 4 pili adhesion

Answer 17

used by N. meningitidis; continually assembles and disassembles, growing from inner membrane, “twitching motility”

Question 18

M protein nonpilus adhesion

Answer 18

used by S. pyogenes; binds to fibronectin in the extracellular matrix between host cells for attachment and invasion of tissues; complement regulatory factor H

Question 19

Pertactin Nonpilus adhesion

Answer 19

used by B. pertussis; binds to host cell integrin for attachment in respiratory tract

Question 20

Exotoxins

Answer 20

proteins produced by various types of bacteria, kill host cells, and unlock nutrients

Question 21

Types of exotoxins

Answer 21

Damage cellular membranes (Alpha toxin)
AB Exotoxins (Anthrax, Cholera, and Shiga toxin)

Question 22

Alpha toxin

Answer 22

found in S. aureus; forms pores in target membranes and red blood cells and causes leakage (responsible for beta hemolysis)

Question 23

Anthrax toxin

Answer 23

in B. anthracis and consists of Edema factor (raises cAMP levels), Lethal factor (cleaves protein kinases), and protective antigen (binds multiple host cell receptors)

Question 24

Cholera toxin

Answer 24

made by V.cholerae via lysogenic phage; binds to intestinal cell membranes, trigger endocytosis of cholera toxin complex, and consists of ADP ribosylates a host cell target that leads to sharp increase in cAMP levels, interferes with ion channels, and massive water loss leading to watery stools

Question 25

Shiga toxin

Answer 25

an AB5 exotoxin produced by Shigella dysenteriae and E.coli O157:H7 that disrupts protein synthesis inhibitors

Question 26

Endotoxins

Answer 26

found in N.meningitidis, part of LPS of Gram negative bacteria (Lipid A), hyper activates immune system to harmful levels

Question 27

How does LPS act as an endotoxin for Gram negative cells?

Answer 27

Lipid A is released as Gram negative bacteria die caused a “cytokine storm” and can trigger fever, shock, and death

Question 28

Three bacterial secretion systems

Answer 28

Type II (pilus like), Type III (syringe like), and Type IV (conjugation system like)

Question 29

Type 2 Secretion System

Answer 29

• used by P. aeruginosa and V. cholerae; a modification of the same system used for type IV pilis biogenesis
• proteins to be secreted first enter the periplasm, then get folded and secreted via and outer membrane pore

Question 30

Type 3 Secretion System

Answer 30

• found in Salmonella, Yersenia, Shigella, and Esherichia species
• a reengineered flagellar synthesis mechanism that uses a molecular syringe to inject proteins from the bacterial cytoplasm directly into host

Question 31

Type 4 Secretion System

Answer 31

• found in A. tumefaciens and B. pertussis
• an evolutionary modification of a conjugation of pilus that secretes protein only, or proteins plus DNA
• allows bacterial pathogens to secrete proteins directly from their cytoplasm or from their periplasms

Question 32

Extracellular avoidance examples

Answer 32

Capsule: prevents phagocytosis
Protein A: prevents opsonization (S. aureus)

Question 33

Intracellular avoidance examples

Answer 33

Hemolysin: used to break out of cell once in phagosome (S.dysenteriae, L.monocytogenes)
Prevent fusion with lysosome (Mycobacterium, Legionalla, and Salmonella)
Mature in acidic environment once fused (C. burnetii)