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Pathogenic Microbiology > LECTURE 10: TB > Flashcards

LECTURE 10: TB Flashcards

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Biology 101 flashcards
1
Q

What are some traits for Mycobacterium?

A
  1. gram positive
  2. aerobes
  3. make catalase
  4. no capsules, flagella, or spores
  5. grow slowly
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2
Q

What are the general characteristics of mycobacterium?

A
  1. very slow growing
  2. protected from lysis once they are phagocytosized
  3. can grow intracellular
  4. resistant to detergents and many common antimicrobial drugs
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3
Q

What is Mycolic Acid?

A

Mycobacteria all produce mycolic acids (mysocides) - long chain hydrophobic fatty acids
Mycolic acid is covalently bound to the peptidoglycan layer of Mycobacteria

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4
Q

What are contained in the main virulence factors of M. TB?

A

contain complex waxes and cord factor that prevent destruction by lysosomes or macrophages

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5
Q

What are the 3 major human mycobacterial infections?

A
  1. Tuberculosis (Mycobacterium tuberculosis)
  2. Leprosy (M. leprae)
  3. Buruli Ulcer (M. ulcerans)
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6
Q

How is TB transmitted?

A
  1. inhalation of droplets from infected individual
  2. aerosolization
  3. skin inoculation
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7
Q

What are the levels on contiguous dependent on?

A
  1. How Close
  2. How Long the exposure
  3. How Many infectious droplet nuclei
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8
Q

What are the 3 clinical divisions of TB?

A
  1. primary tuberculosis
  2. secondary tuberculosis (reactivation or reinfection)
  3. disseminated tuberculosis
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9
Q

What is the pathogenicity of primary TB?

A
  1. infection begins when the bacteria reach the alveoli
  2. Use pili to attach to extracellular human protein laminin
  3. Phagocytose by alveolar macrophages
  4. Macrophages are unable to digest them partly because mycobacteria prevent fusion of lysosomes with phagosomes.
  5. Multiply intracellularly
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10
Q

How is Primary TB synthesized?

A
  1. Replication inside the macrophages induce a localized proinflammatory response
  2. Leads to the recruitment of mononuclear cells from neighboring blood vessels.
  3. These cells are the building blocks for the granuloma, or tubercle, that defines the disease.
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11
Q

How do granuloma benefit the bacteria?

A

recruits macrophages that serve as additional sanctuaries for bacterial growth and population expansion

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12
Q

How is secondary/reactivated TB come about?

A

After several years to decades of latent TB infection (LTBI)
Occurs with waning cell-mediated immunity
Local or systemic stress, another illness, advancing age…

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13
Q

what happens to tubercles in secondary/reactivated tuberculosis?

A

If patient doesn’t recover from primary tuberculosis, reactivation of bacilli can occur.
Tubercles expand and drain into the bronchial tubes and upper respiratory tract.
Gradually the patient experiences more severe symptoms
Untreated, a 60% mortality rate

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14
Q

What is disseminated TB?

A

During secondary TB, bacilli disseminate to regional lymph nodes, kidneys, long bones, genital tract, brain, and meninges.
These complications are grave.

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15
Q

What are the predisposing factors for TB?

A
  1. inadequate nutrition
  2. debilitation of the immune system
  3. poor access to medical care
  4. lung damage
  5. Genetics
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16
Q

What are the diagnosis procedures of TB?

A
  1. Mantoux test - in vivo or tuberculin testing
  2. X rays
  3. direct identification of acid fast bacilli in specimen
  4. cultural isolation and biochemical testing
17
Q

What are the limitations of the Mantoux TB skin test?

A

Not sensitive (false-negatives)

  • 20% of normal hosts with active TB do not react
  • Up to 80% of HIV-infected persons with TB do not react
18
Q

What are the various IGRA testings?

A

interferon gamma release assays, they measure ifn gamma response of whole blood cells to TB antigens, whole blood from patient is incubated with TB proteins to detect presence of sensitized WBCs as evidence of prior TB infection.

19
Q

How are chest X-rays used to diagnose TB?

A

Abnormalities often seen in apical or posterior segments of upper lobe or superior segments of lower lobe
May have unusual appearance in HIV-positive persons
cannot confirm diagnosis of TB

20
Q

Why is TB considered acid fast?

A

they hold onto the first dye during an acid fast test and resist the acid wash

21
Q

Why are culture for TB very useful?

A

Used to confirm diagnosis of TB

22
Q

What are the managements to prevent TB?

A

6-24 months of at least 2 drugs - Rifater

23
Q

How can you prevent drug resistance in TB?

A

Many patients start feeling better after a month of antibiotic therapy and stop using antibiotics - which leads to more drug-resistant bacteria.

24
Q

What is multi-drug resistant TB (MDR)?

A

Implies resistant to at least INH and RIF

Associated with up to 50% failure

25
Q

What is XDR TB?

A

EXtensively Drug-Resistant tuberculosis – by definition resistant to INH, rifampin and quinolones

26
Q

what are some traits of the cord factor?

A
  1. give culture media the corded look
  2. causes weight loss
  3. binds cells of M. tuberculosis so they are further resistant to immune system
27
Q

what are tubercles?

A

small, hard nodules formed when macrophages surround and phagocytosize M. tuberculosis

28
Q

what causes caseous necrosis?

A

the release of M. tuberculosis when the infected cells within the tubercle in the center die

29
Q

what is a tuberculous cavity?

A

when the center of the tubercle liquefies and becomes filled with air

30
Q

how do granulomas benefit the host?

A

granulomas represent sites for optimal interactions between pathogen-infected antigen presenting cells, such as macrophages and DCs, in close apposition to effector T-lymphocytes, to allow for immune control of mycobacterial infection.

31
Q

What are the symptoms of secondary TB?

A

violent coughing, greenish or bloody sputum, fever, anorexia, weight loss, fatigue

32
Q

What is DOT?

A

directly observed treatment, refers to a TB control strategy that combines 5 different components

Pathogenic Microbiology (12 decks)

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