Microbio 3 Flashcards

1
Q

Shigella

[Px]

A

Invades GI mucosa via M cells that overlie Peyer’s patches – lyse containment vacuole, enter cytosol – apoptosis – spread to adjacent cells.
*Shiga toxin is a minor player since there are nontoxigenic strains that cause Shigellosis.

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2
Q

What is the importance of env gene in HIV replication?

A

env gene encodes gp160, which is cleaved and modified into gp120 and gp41.
>gp120: viral attachment binding to CD4 receptor of T cells (CCR5).
>gp41: transmembrane, fusion b/w virus and target cells.

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3
Q

Norovirus

disease, presentation, outbreaks where

A

MCC of viral gastroenteritis (adults).
>Watery diarrhea w/o blood or mucus.
>Outbreaks in crowded settings (schools, hospitals).
>Acute onset w/ quick resolution (2-3 days).
*Resistant to inactivation by acid, bile, pancreatic enzymes.

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4
Q

TB treatment drugs

[MOA]

A

> Rifampin: inhibits DNA-dependent RNAp.
Isoniazid: inhibits mycolic acid synthesis (cell wall structure and virulence).
Pyrazinamide: unclear MOA.
Ethambutol: inhibits arabinosyl transferase.

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5
Q

TB treatment drugs

[SE]

A

> Rifampin: rash, red-orange body fluids, cytopenias, GI side effects (vomiting).
Isoniazid: neurotoxic (give B6), hepatotoxic.
Pyrazinamide: hyperuricemia, hepatotoxic.
Ethambutol: optic neuropathy.

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6
Q

Pertussis (whooping cough)

[Cause, virulence factors, phases]

A

B. pertussis
>Virulence: adhesins, toxins (Pertactin, tracheal cytotoxin, adenylate toxin, pertussis toxin).
>3 phases: Catarrhal stage, Paroxysmal stage (severe coughing w/ whoop), Convalescent stage.

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7
Q

Pasteurella

[Disease, characteristic]

A

Mouths of dogs (cats).
Most skin infections (cellulitis, osteomyelitis) caused by dog bites
Infection w/in 24 hrs of inoculation.
>Mouse-like odor (indole-positive species)

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8
Q

What does H. influenzae type b virulence depend on?

A

Polysaccharide capsule made of polyribosylribitol phosphate (PRP).
PRP binds to Factor H, a complement control protein that prevents complement deposition on host cells – degrades C3b – no opsonization, no phagocytosis.

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9
Q

Aspergillus

[Diseases]

A

Widely distributed in environment, decaying veggies, monomorphic (mold form only).
>Invasive aspergillosis
>Aspergilloma (fungus balls)
>Allergic bronchopulmonary aspergillosis

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10
Q

What’s significant about compound muscle action potential in botulism?

A

Botulism presents w/ diplopia, dysphagia, and dry mouth.
These effects can be partially overcome by high-rate repetitive nerve stimulation to facilitate compound muscle muscle action potential (CMAP), since excitation at the NMJ is inhibited in botulism.

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11
Q

Nonbullous impetigo.

[Causes, ssx, complications]

A

May be caused by S. aureus or S. pyogenes (labs).
>Painful non-itchy pustules; Honey-crusted lesions (perioral).
>Can lead to PSGN – immune complex deposition on GBM, complement activation.

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12
Q

Bronchiolitis

[Cause, ssx, findings]

A

MCC is RSV; lower respi tract infection.
>Rhinorrhea, congestion –> cough, low-grade fever, inc. work of breathing.
>Findings: hypoxemia, tachypnea, retractions and nasal flaring (respi distress)

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13
Q

Why is it difficult to make a vaccine for Hepatitis C virus?

A

High mutation rate and no proofreading in its RNA-dependent RNAp – prone to errors during replication – can have several quasispecies or variant strains in one person.
Hypervariable genes can code for envelope – host can’t mount an effective immune response – antibodies for one variant but not others.

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14
Q

What contributes to Mycobacteria’s virulence?

A

Cord factor: a mycoside that inactivates neutrophils, damages mitochondria, induces TNF release.
*W/o cord factor, there would be no disease.

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