Lessons 1-3 Flashcards
Concepts Introduced in first 3 Classes (38 cards)
1
Q
Vibrio Cholerae
A
- Gram negative, γ-proteobacterium, motile.
- Causes cholera, fecal-oral transmission
- Lives in Aquatic Environments. Quorum sensing induces biofilm formation.
- Chitin, High cell density induce natural competence
- Toxin-coregulated pilus important for adhesion to intestine.
2
Q
Gram negative Bacteria
A
- do not retain the crystal violet stain
1. An inner cell membrane is present (cytoplasmic)
2. A thin peptidoglycan layer is present
3. Has outer membrane containing lipopolysaccharides (LPS, which consists of lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet
4. periplasm
5. The S-layer is directly attached to the outer membrane rather than to the peptidoglycan
3
Q
Gram positive Bacteria
A
- take up the crystal violet stain
1. Cytoplasmic lipid membrane
2. Thick peptidoglycan layer
3. Teichoic acids and lipoids are present, forming lipoteichoic acids, which serve as chelating agents, and also for certain types of adherence.
4. Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase.
5. A much smaller volume of periplasm than that in Gram-negative bacteria.
4
Q
Cholera
A
- Currently in 7th, 8th pandemics.
- Spread through infected food/water (open-air toilets, lack of clean water, no sewage treatment, contact w/ environmental water.)
- Severe, watery diarrhea, rapid dehydration
- Treatment: Oral rehydrating salts, not antibiotics
Virulence Factors:
- Toxin-coregulated Pilus: Mediates micro colony formation. Facilitates adhesion to intestinal epithelium.
- Cholera Toxin: activates adenylate cyclase secondary messenger pathway. An A-B5 subunit-type exotoxin. Released in small intestine. Responsible for secretory diarrhea, direct stimulation of chloride secretion by enterocytes and enteric nervous system. Induces exocytosis of mucins.
5
Q
V. cholerae DNA uptake machinery
A
- Competence Pili: Type IV pilus. Composed of PilA monomers, and penetrates outer membrane through PilQ pores. Harnesses DNA in the extracellular environment and draws it into the outer membrane.
- ComEA: reels DNA into the periplasm and condenses it. DNA may be stored this way in the periplasm. Uptake to the cytoplasm spatially, but not temporally, linked. ComEC necessary for uptake.
- Type VI Secretion System: Part of competence regulon (originally suggesting function in competence). Predatory function -> Prey DNA release. Kin-discrimination through immune proteins. Delivers cell-wall degrading enzymes, pore forming toxins, lipases.
- Competence regulon activated by high cell density ( –> HapR -> qstR ) and chitin ( –> TfoX –> pil_operon, qstR ). QstR -> comEC, comEA, T6SS genes.
6
Q
V. cholerae replication inside Amoebae
A
A. castellanii: - phagocytosis - occasional shuffling from endosomal vacuole to contractile vacuole - colonization of CV - CV lysis and cell lysis D. discoideum: Just toxic
7
Q
Def. Infectious Disease + Mortality
A
- Def: Pathological condition of body parts or tissue characterized by an identifiable group of symptoms, caused by an infectious agent
- Causes 1/3 - 1/4 of Deaths, >50% in children <5 y.o.
- Top 3 single agents: HIV, Malaria, Tuberculosis.
8
Q
Virulence
A
The relative ability of an agent to cause rapid and sever disease in a host
9
Q
Phases of Infectious Disease
A
- Incubation period: Time between infection and symptoms
- Prodromal: General, mild symptoms
- Clinical: Typical symptoms
- Decline: What it sounds like
- Recovery: Disappearance of symptoms, regain strength, heal tissues
10
Q
Epidemics and pandemics
A
Epidemic: an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area. An outbreak is the same but local to a specific area.
Pandemic: an epidemic with a large geographic area.
Endemic: constant pressure, occurrence, in an area or population.
11
Q
Yersinia Pestis - Plague
A
- Bacterial
- From rodent/flea bites or inhalation from other inf. people
- (Bubonic) swollen glands, (pneumonic) fever, extreme exhaustion, breathing difficulty
- Prev: avoid contact with fleas, animals + antibiotics
- Impact: Killed 1/3 of Europe’s population from 1348-1350.
Bubonic plague is most common.
Pneumonic plague infects the lungs and could be used in an aerosol bioterror attack. Can also be spread p2p by coughing and sneezing.
Septicemic plague can be a complication of bubonic or pneumonic plague, is systemic, and cannot spread p2p. Shock.
12
Q
Tuberculosis
A
- Mycobacterium tuberculosis
- Usually attacks lungs, but can also affect kidneys, brain
- person-to-person transmission
- Bad (bloody) cough, Chest pain
- Prev: good ventilation, skin tests, treatment if active
- 1/3 of world pop thought to be infected, 2M deaths/year
T. bacillus exploits macrophage as niche of replication, prevents fusion of phagosome and lysosome, does not acidify.
To be infectious, bacterium must reach lower respiratory tract. Can be cyclically symptomatic and cured individuals can get reinfected.
MDR-TB present in virtually all countries.
13
Q
Malaria
A
- 4 protozoan parasites (Plasmodium)
- High fever, flu-like illness
- Prev: avoid mosquito bites, take region-specific anti-malarials
- 300-500M cases per year -> 1 M deaths/year
14
Q
AIDS
A
- Human immunodeficiency virus
- Sex, inf. needles/syringes, transfusions, mother-to-infant transmission
- Destroyes immune system -> opportunistic infections, cancer
- Prev: safe sex, sterile needles, testing transfusions, antiretrovirals.
Impact: Leading cause of death in 15-49 y.o., 1.7M deaths in 2011.
15
Q
Yellow Fever
A
- Viral
- Mosquitos
- Jaundice, Fever, Kidney Failure
- Prev: Vaccine, avoid mosquito bites
- Common in rural sub-saharan African and South America
16
Q
Polio
A
- poliovirus, highly-infectious, fecal-oral
- person-to-person spread
- Fever, vomiting, neck stiffness, muscle atrophy,
- 1 in 200 -> irreversible paralysis.
- 1 in 2000-4000, Death
- Endemic in India, Nigeria, Pakistan, Afghanistan
17
Q
Measles
A
- Viral, Highly Infectious
- Respiratory Disease, coughing, sneezing, Koplik’s spots, rash, high, diarrhea, fever, pneumonia, encephalitis, seizures
- 100K Deaths per year
- Most severe symptoms in undernourished, immune-compromised children. Diarrhea most common cause of death.
- Before vaccine, most children contracted measles.
18
Q
Smallpox
A
- Variola virus
- Person-to-person + contaminated bedding, clothing
- High fever, rash, permanent scarring.
- Eliminated 1978
- 300-500M deaths, 20th century
Vaccine made from live vaccinia virus. Requires bifurcated needle
19
Q
Influenza A
A
- Viral
- Respiratory, spread by sneeze/cough droplets
- Fever, severe malaise, intestinal upset
- Prev: Vaccine
- about 3 pandemics/century. 20th century: Spanish, Asian, Hong Kong
- Defined by hemagglutinin (15 subgroups) and neuraminidase (9 subgroups)
Sialic Acid Receptors:
- humans: Upper: α2-6, lower: α2-3
- birds: α2-3 in intestine
Avian flu infection in humans is rare but severe (lower respiratory tract infection, 30-60% mortality in hospitalized patients), but a receptor change to bind α2-6 sialic acid makes it highly infectious in humans.
20
Q
B. pertussis
A
- Gram -
- Causes whooping cough (“100 day cough”)
- Violent, uncontrollable coughing.
- related to B. parapertussis.
- Incidence increasing in countries with high vaccine coverage, because aPv does not provide life-long coverage.
21
Q
aPv
A
- Requires multiple vaccines.
- Almost wholly Th2 mediated response -> poor protection in infants until 6mo., risk of extensive swelling from sensitivity to high antibody titers.
- Contain >= 1 of highly purified antigens: PT, FHA, PRN, and FIM type 2 / 3
22
Q
wPv
A
- based on standardized cultures of selected B. pertussis strains
- heterogenous
BPZE1: live, single dose, long-lasting immunity, protection from B. parapertussis, should protect infants, balanced with Th1 arm response.
23
Q
TCT - Tracheal Cytotoxin
A
Breakdown product of peptidoglycan, responsible for the destruction of tracheal cilia in pertussis. Eliminated in BPEZ1 with more efficient importer from E. coli, reused in cell wall synthesis.
24
Q
PTX - Pertussis Toxin
A
Major virulence factor, but also protective factor. Responsible for systemic effects of PTX. Mutated -> Inactive
25
DNT - Dermonecrotic factor
Lethal activity upon injection, but role in virulence unknown. Removed by allelic exchange.
26
Th1 Immunity
Cytokine: IFN-γ -> IgG2a -> Cellular immunity, directed towards intracellular pathogens, proinflammatory
27
Th2 Immunity
Cytokines: IL-4/IL-5 -> IgG1 -> Anti-inflammatory, humoral immunity.
28
H & E stain
- principal stain in histology.
- Hemotoxylin stains basophilic substances (nucleotides) blue.
- Eosin stains acidophilic substances (membranes, extracellular fibers) red.
29
Toluine Blue
Stains acids (nucleotides) blue, polysaccharides and mast cells purple.
30
Confirming pathogenicity
- Earliest methodology for proving pathogenicity: Koch's postulates. Isolate path. -> Culture -> reintroduce + Observe disease -> Reisolate and confirm the same pathogen.
Alternatives:
- Biochemistry to identify pathogen in diseased tissue (PCR, immunohistochemistry, ...)
- Therapy to eliminate pathogen -> disappearance of disease
- Vaccination/better practices to prevent disease
Example: H. pylori -> Introduction of H. pylori in patients caused gastric ulcer, elimination lead to recovery.
31
Virulence Factors
enable a microorganism to establish itself on or within a host of a particular species and enhance its potential to cause disease
Functions:
- adhesion (pili, or afimbrial, adapted to low or high shear stress)
- immune evasion
- intracellular growth
- intoxication
32
Type IV pili
- Neisseria gonorrhoeae & E. coli
- Form bundles. Nutrient gradient-directed "random walk". Can also be used to attach to surfaces, and move through extension and retraction.
- Assembled by PilF
- Disassembled by PilT
- PilD prepares PilA.
- Capping pilins
33
Extracellular Immune avoidance
- Capsule formation (Streptoccocus pneumoniae), hides ag.
- Protein A (S. Aureus), binds wrong ends of ab.
- Trigger apoptosis (H. pylori)
- Escape from Phagosome (Shigella, Listeria)
- Prevent fusion of phagosome w/ lysosome (Salmonella, Mycobacteria)
-
34
Listeria monocytogenes life cycle
- Enters host cell by attaching to E-cadherin with Internalin A/B and zippering in.
- Acidify vacuole w/ LLO
- Lyse phagosome Plc A/B
- ActA to polymerize actin
- Rocket into nearby cell & repeat w/ LLO + PLCs
35
LPS - an endotoxin
From most external to most internal:
- repeating O-specific polysaccharide subunit
- outer core oligosaccharide
- inner core oligosaccharide
- lipid A
Recognized by TLR. Immune response to LPS leads to fever and sepsis, which can be worsened with antibiotics (massive bacterial death)
36
Exotoxins
1. Membrane Damaging Toxins (30%):
Pore-forming toxins: ex. α-Toxin. Has to bind to lipid receptor in membrane, and then form oligo-unit to form structural pore. Leads to leakage of ions, and macromolecules. Bacteria protect themselves by not having necessary anchors in membrane to integrate toxins.
2. Inhibit Protein synthesis:
- Shiga toxin (AB5) interferes with ribosomal function. Needs to be processed via ERAD.
- ERAD: Phagocytosis -> misdirects early endosome -> retrograde traffic thru trans-golgi network -> reducing env. of ER disassociates A1 from holotoxin-> HEDJ transport through membrane -> Escapes proteasome degradation because it has no lysine residues.
- S. dysenteriae protects itself because Shiga toxin targets eukaryotic ribosomal subunit 28s.
3. Activate 2nd Messenger Pathway:
- Cholera Toxin - Activates adenylate cyclase - increased cAMP. AB5 toxin. V. cholerae protected because it does not have GB3 receptor on cell surface.
4. Proteases:
- Anthrax (lethal factor), Botulinum, Tetanus
5. Superantigens:
- Bind to TCR. Hyperactivation of T-cell. Bacteria protected because they have no TCR.
37
Secretion Systems
Type II:
- General secretion pathway
- 2 step pathway (-> periplasm via translocator ->)
Type III:
- Injectisome: effector proteins delivered directly into eukaryotic cell (Sec dependent).
- Genetically, structurally, functionally related to flagella.
- Salmonella, shigella, yersinia, EPEC, EHEC
Type IV:
- Wide range of bacteria (G -/+) for a wide range of substrates
Type VI:
- In 25% of Gram -
- Structurally & functionally related to phage tails, but topologically reversed.
- Pseudomonas, Burkholderia, Vibrio
- VipA/B form sheath. Hcp forms needle, ClpV necessary to dismantle T6SS, but nonessential for function.
- Highly dynamic, spontaneously contractile, usually 1 per cell.
38
Electron Cryotomography
static imaging modality, show to preserve and reveal bacterial cytoskeletal structures directly in 3D in a near-native, life-like state
