Mechanisms of Microbial Infections

Question 1

Microbes ranked smallest to largest

Answer 1

prions, viruses, bacteria, fungi, protozoa

Question 2

What size organisms get trapped in the nasal cavity and turbinates? What size can get into bronchioles, etc.?

Answer 2

2um; 1um

Question 3

Mucus layer in GI tract is composed of

Answer 3

An inner gel layer, and outer soluble layer

Question 4

Mucus layer in the respiratory tract is composed of

Answer 4

Luminal viscoelastic/gel layer to trap fomites, and a serous inner layer where the cilia beat

Question 5

What bacteria colonizes mucus (and goblet cells)?

Answer 5

Brachyspira hyodysenteriae- spirochetes chemotax to mucus

Question 6

What bacteria colonize cilia?

Answer 6

Mycoplasma

Question 7

What bacteria colonize the cell through endocytosis

Answer 7

Lawsonia intracellularis

Question 8

What agent enters through M cells?

Answer 8

Porcine circovirus type 2 (PMWS)

Question 9

What agent uses direct entry (motility) to infect target cell?

Answer 9

Leptospira spp.

Question 10

What agent uss transcytosis entry?

Answer 10

Erysipelothrix rhusiopathiae

Question 11

What agent uses basolateral membrane for entry into target cells? Apical membrane?

Answer 11

Parvovirus; influenza virus

Question 12

What agent uses dendritic cells to access MALT

Answer 12

Poxviruses

Question 13

What agent uses Trojan Horse entry (leukocyte trafficking)

Answer 13

Rhodococcus equi

Question 14

What agent releases bacterial enzymes to digest the mucus layer in the alimentary tract?

Answer 14

Clostridium

Question 15

Who usually secretes exotoxins?

Answer 15

Gram positive bacteria

Question 16

What is responsible for the toxicity of LPS? What is responsible for the immunogenicity of LPS?

Answer 16

Lipid A component; polysaccharide component

Question 17

What bacteria use Type III Secretion Systems? Type IV?

Answer 17

Salmonella and E.coli; Brucella abortus

Question 18

Difference between conjugation, transformation, and transduction? What are these an example of?

Answer 18

Conjugation- direct contact, via plasmids
Transformation- free DNA taken up by bacteria
Transduction- bacteriophage (virus) carries DNA to other bacteria
Horizontal gene transfer

Question 19

What aids adhesion of uropathogenic E.coli? Enterotoxigenic?

Answer 19

Fimbrial adhesins (I, P, S/F1C)
Pilus adhesin (K99)

Question 20

What aids invasion of Clostridium chauveoi?

Answer 20

Invasins- enzymes lecithinase and phospholipase punches holes in cells

Question 21

What bacteria use AB system exotoxins? How does this work?

Answer 21

Bacillus anthracis, C. botulinum, C. tetani, Corynebacterium renale; B toxin binds, A toxin enters cytoplasm

Question 22

What toxin does Staph aureus use? What kind is it and what does it do? What other virulence factor does staph use?

Answer 22

Alpha toxin; Pore forming cytotoxin; directly toxic by forming pores; Bap- biofilm associated protein

Question 23

Most sensitive cells to LPS?

Answer 23

Endothelial cells, platelets, macrophages

Question 24

What toxin from Gram positive bacteria mimics LPS?

Answer 24

lipoteichoic acid

Question 25

What siderophore do Salmonella and E.coli use? Bacillus anthracis?

Answer 25

Enterobactin; bacillibactin

Question 26

Pathogenesis of E.Coli (edema disease)

Answer 26

Release of Shiga toxin 2e (verotoxin 2e) that binds receptors (Gb3 or Gb4) on endothelial cells and smooth muscle cells of vessels

Question 27

Virulence factors of Salmonella

Answer 27

Pathogenicity islands T3SS system Enterobactin (siderophore)

Question 28

How does C. perfringens glide and attach? What are the alpha, beta, epsilon, and iota toxins?

Answer 28

Type IV pili Alpha- phospholipase, lecithinase Beta- pore-forming (trypsin labile) Epsilon- pore-forming (trypsin activated) Iota- disrupts cytoskeleton

Question 29

Only gram negative clostridium

Answer 29

C. piliforme

Question 30

How does the bacillus anthracis AB toxin system work?

Answer 30

B is protective antigen (PA), binds TEM8; A toxins are edema factor and lethal factor

Question 31

What helps MAP bind iron? Where does it enter ileum?

Answer 31

Exochelins; M cells

Question 32

VIrulence factor of clostridium haemolyticum

Answer 32

Phospholipase C aka beta toxin- lecithinase, pore-forming

Question 33

Virulence factor of clostrifium novyi type b (black disease)

Answer 33

Phospholipase C, but less than haemolyticum so no hemolysis

Question 34

Pathogenesis of rhodococcus

Answer 34

Coughed up, swallowed, binds M cells, VAPs (virulence associated proteins) block fusion of phagolysosome

Question 35

Exotoxin of mannheimia haemolytica and actinobacillus pleuropneumoniae

Answer 35

Mannheimia- Leukotoxin (RTX), neuraminidase, capsular polysaccharides Actinobacillus- Apx I-III (RTX)

Question 36

What causes atrophic rhinitis? What are the toxins?

Answer 36

Bordetella and pasteurella type D Bordetella- Dermonecrotic toxin (DNT) Pasteurella- P.multocida toxin (PMT), which is an A-B dermonecrotic toxin that increases osteoclasts

Question 37

Pathogenesis of leptospirosis

Answer 37

Invasive motility, penetrates PCT cell from basolateral aspect via capillaries

Question 38

Botulinum toxin mechanism

Answer 38

A-B, works at myoneural junctions B domain binds neuron, A cleaves SNARE, so AcCh can't be released

Question 39

Tetanospasmin toxin mechanism

Answer 39

A-B, works at inhibitory interneurons B domain binds neuron, A cleaves SNARE, so GABA can't be released (inhibitory)

Question 40

Listeria virulence factors

Answer 40

Type A and B internalins, target E-cadherins for entry Retrograde axonal transport from oral mucosa to brain Actin-based motility propels bacteria, forming pseudopod into adjacent cell Listeriolysin O, phospholipase C, lecithinase lyse vesicle

Question 41

What PAMPs do histoplasma have?

Answer 41

Alpha and beta glucans in yeast cell walls

Question 42

What antioxidant defenses does Aspergillus have?

Answer 42

Melanin pigment, beta glucans

Question 43

Virulence factors of Cryptococcus

Answer 43

Phospholipases- injure pneumocytes Capsule negative charge inhibits phagocytosis Melanin- antioxidant

Question 44

Blastomyces adhesin; other virulence factor

Answer 44

BAD1, conidia bind to alveolar macrophages via CR3 and CD14; melanin

Question 45

Which virulence factors digest fibrin and prevent clotting?

Answer 45

Kinases