Mechanisms of Microbial Infections Flashcards
PBVD Ch. 4
Microbes ranked smallest to largest
prions, viruses, bacteria, fungi, protozoa
What size organisms get trapped in the nasal cavity and turbinates? What size can get into bronchioles, etc.?
2um; 1um
Mucus layer in GI tract is composed of
An inner gel layer, and outer soluble layer
Mucus layer in the respiratory tract is composed of
Luminal viscoelastic/gel layer to trap fomites, and a serous inner layer where the cilia beat
What bacteria colonizes mucus (and goblet cells)?
Brachyspira hyodysenteriae- spirochetes chemotax to mucus
What bacteria colonize cilia?
Mycoplasma
What bacteria colonize the cell through endocytosis
Lawsonia intracellularis
What agent enters through M cells?
Porcine circovirus type 2 (PMWS)
What agent uses direct entry (motility) to infect target cell?
Leptospira spp.
What agent uss transcytosis entry?
Erysipelothrix rhusiopathiae
What agent uses basolateral membrane for entry into target cells? Apical membrane?
Parvovirus; influenza virus
What agent uses dendritic cells to access MALT
Poxviruses
What agent uses Trojan Horse entry (leukocyte trafficking)
Rhodococcus equi
What agent releases bacterial enzymes to digest the mucus layer in the alimentary tract?
Clostridium
Who usually secretes exotoxins?
Gram positive bacteria
What is responsible for the toxicity of LPS? What is responsible for the immunogenicity of LPS?
Lipid A component; polysaccharide component
What bacteria use Type III Secretion Systems? Type IV?
Salmonella and E.coli; Brucella abortus
Difference between conjugation, transformation, and transduction? What are these an example of?
Conjugation- direct contact, via plasmids
Transformation- free DNA taken up by bacteria
Transduction- bacteriophage (virus) carries DNA to other bacteria
Horizontal gene transfer
What aids adhesion of uropathogenic E.coli? Enterotoxigenic?
Fimbrial adhesins (I, P, S/F1C)
Pilus adhesin (K99)
What aids invasion of Clostridium chauveoi?
Invasins- enzymes lecithinase and phospholipase punches holes in cells
What bacteria use AB system exotoxins? How does this work?
Bacillus anthracis, C. botulinum, C. tetani, Corynebacterium renale; B toxin binds, A toxin enters cytoplasm
What toxin does Staph aureus use? What kind is it and what does it do? What other virulence factor does staph use?
Alpha toxin; Pore forming cytotoxin; directly toxic by forming pores; Bap- biofilm associated protein
Most sensitive cells to LPS?
Endothelial cells, platelets, macrophages
What toxin from Gram positive bacteria mimics LPS?
lipoteichoic acid
What siderophore do Salmonella and E.coli use? Bacillus anthracis?
Enterobactin; bacillibactin
Pathogenesis of E.Coli (edema disease)
Release of Shiga toxin 2e (verotoxin 2e) that binds receptors (Gb3 or Gb4) on endothelial cells and smooth muscle cells of vessels
Virulence factors of Salmonella
Pathogenicity islands
T3SS system
Enterobactin (siderophore)
How does C. perfringens glide and attach? What are the alpha, beta, epsilon, and iota toxins?
Type IV pili
Alpha- phospholipase, lecithinase
Beta- pore-forming (trypsin labile)
Epsilon- pore-forming (trypsin activated)
Iota- disrupts cytoskeleton
Only gram negative clostridium
C. piliforme
How does the bacillus anthracis AB toxin system work?
B is protective antigen (PA), binds TEM8; A toxins are edema factor and lethal factor
What helps MAP bind iron? Where does it enter ileum?
Exochelins; M cells
VIrulence factor of clostridium haemolyticum
Phospholipase C aka beta toxin- lecithinase, pore-forming
Virulence factor of clostrifium novyi type b (black disease)
Phospholipase C, but less than haemolyticum so no hemolysis
Pathogenesis of rhodococcus
Coughed up, swallowed, binds M cells, VAPs (virulence associated proteins) block fusion of phagolysosome
Exotoxin of mannheimia haemolytica and actinobacillus pleuropneumoniae
Mannheimia- Leukotoxin (RTX), neuraminidase, capsular polysaccharides
Actinobacillus- Apx I-III (RTX)
What causes atrophic rhinitis? What are the toxins?
Bordetella and pasteurella type D
Bordetella- Dermonecrotic toxin (DNT)
Pasteurella- P.multocida toxin (PMT), which is an A-B dermonecrotic toxin that increases osteoclasts
Pathogenesis of leptospirosis
Invasive motility, penetrates PCT cell from basolateral aspect via capillaries
Botulinum toxin mechanism
A-B, works at myoneural junctions
B domain binds neuron, A cleaves SNARE, so AcCh can’t be released
Tetanospasmin toxin mechanism
A-B, works at inhibitory interneurons
B domain binds neuron, A cleaves SNARE, so GABA can’t be released (inhibitory)
Listeria virulence factors
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
What PAMPs do histoplasma have?
Alpha and beta glucans in yeast cell walls
What antioxidant defenses does Aspergillus have?
Melanin pigment, beta glucans
Virulence factors of Cryptococcus
Phospholipases- injure pneumocytes
Capsule negative charge inhibits phagocytosis
Melanin- antioxidant
Blastomyces adhesin; other virulence factor
BAD1, conidia bind to alveolar macrophages via CR3 and CD14; melanin
Which virulence factors digest fibrin and prevent clotting?
Kinases
