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Micro and Immunology > Mycobacteria > Flashcards

Mycobacteria Flashcards

1
Q

What is the morphology of myocobacteria?

A

Slender, rod-shaped

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2
Q

Describe the growth pattern, and staining pattern.

A

Slow growing

Poor staining and acid fast

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3
Q

What does acid fast mean?

A

Once stained, resistant to decolourization by acid

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4
Q

What is peculiar of the cell wall of mycobacteria?

A

60% lipid - including long chain fatty acids called mycolic acids

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5
Q

Why are mycobacteria so tough?

A

Unique composure makes them resistant to the environment and, they live inside cells

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6
Q

What are the different mycobacteria classifications?

A
  1. Tubercle bacilli complex (cause TB)
  2. MOTT - mycobacterium other than tubercle bacilli
  3. Mycobacterium leprae (causal agent of leprosy)
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7
Q

What bacterium causes leprosy?

A

Mycobacterium leprae

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8
Q

What is the mycobacterium from cattle?

A

Mycobacterium bovis

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9
Q

What proportion of the world is infected with tuberculosis?

A

1/3rd

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10
Q

How does the TB infection become airborne?

A

IF it aerosolizes - mostly coughing (singing and talking too)

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11
Q

Why are aerosols so dangerous?

A

They are carried by air currents and can infect someone very far away

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12
Q

If the sputum stain returns negative for AFB, what does that mean?

A

There are not enough bacteria to cause infections - i.e. the person is non-infectious

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13
Q

What does AFB stand for?

A

Acid-fast bacillus

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14
Q

Although the incidence of TB is very low in NA, which groups have higher rates?

A

Inuit, First Nations, refugees, AIDS and homeless

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15
Q

What is the hallmark of TB?

A

A tubercle = caseating granuloma

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16
Q

Pulmonary TB is ___________ at first, with insidious onset of _______.

A

asymptomatic

cough

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17
Q

_______ infectious patients may seem in good health for long periods (TB).

A

highly

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18
Q

What symptoms are often seen before the lesion is seen on a chest X-ray?

A

Hemoptysis, weight loss and fever

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19
Q

Most pulmonary TB in adults is located where in the lungs?

A

Apical areas

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20
Q

How did the TB get to the apical areas of the lungs?

A

TB spreads via air current - breathed in and goes to lower lung fields.
TB travels through the blood from the primary focus to the apical areas

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21
Q

What is the only tissue in which we cannot get TB?

A

enamel

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22
Q

Describe extrapulmonary TB.

A

15% of cases
Acquired via hematogenous seeding (blood)
almost non-contagious

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23
Q

Most people infected with TB do not develop TB, but, how can it be activated?

A

when the patient becomes immunocompromised

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24
Q

What are some reasons that latent TB may become active?

A

organ transplant, chemotherapy or other debilitating disease

rapid, inadvertent weight loss

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25
Q

What is currently used to determine if somone has been infected by TB?

A

Mantoux skin test

26
Q

What is primed to replace the Mantoux skin test?

A

Interferon gamma release assay

27
Q

What is the Mantoux skin test (i.e. what is done)?

A

Intradermal injection of 5 tuberculin units of PPD (purified protein derivative)

28
Q

What is measured after administration of the 5 tuberculin units of PPD?

A

Induration (not erythema)

29
Q

The induration is measured after how much time has expired? Thus, what day is a Mantoux test not administered?

A

48-72 hours

Not administered on Thursdays

30
Q

For individuals of high risk for TB (suspicious chest X-ray, contact cases, immunosuppressed), what is a positive result?

A

Any induration bigger or equal to 5mm

31
Q

For individuals of moderate risk (i.e. high prevalence countries, healthcare workers, prison or instituations) are positive at what induration size?

A

bigger or equal to 10 mm

32
Q

If a person has no risk factors, what is a positive skin test TB result?

A

induration bigger or equal to 15 mm`

33
Q

What’s a great way to increase measurement precision for TB skin test?

A

Take ballpoint pen and you will feel where the induration starts.

34
Q

How can the sensitivity of the TB skin test be increased?

A

Increased with 2 tests a few weeks apart - two step test

35
Q

Repeating testing _____ lead to false positives.

A

doesn’t

36
Q

How long does it take after exposure to develop a positive test result?

A

4-6 weeks

37
Q

What is paradoxical about those with advanced TB?

A

They may become anergic and have a negative test (i.e. don’t respond to any skin test antigens)

38
Q

Is there a TB vaccine?

A

BCG vaccine give to infants in many higher TB area countries

39
Q

Can a BCG vaccine cause a positive skin test?

A

Yes, but for only a few years; i.e. a positive test in an adult should not be ascribed to a childhood BCG vaccine

40
Q

MOTT-related diseases are often seen in what individuals?

A

the immunosuppressed

41
Q

MOTT can colonize where without causing disease?

A

the respiratory tract

42
Q

MOTT is the cause of what?

A

most pulmonary disease, local lymphadenitis, bone and joint or skin/soft tissue infections

43
Q

What type of immunity is essential against mycobacteria?

A

T cell immunity

44
Q

What is another word for true leprosy?

A

Hansen’s disease

45
Q

Chronic infection of the skin, peripheral nerves and, in ________ _______, the nasal mucosa.

A

leprosy

lepromatous leprosy

46
Q

How do peripheral nerves become palpable in leprosy?

A

Peripheral nerves are infiltrated by large numbers of AFB

47
Q

What is the real cause of the loss of digits in leprosy?

A

Sensory deficits occur and thus trauma is the real cause of loss of digits

48
Q

Lepromatous cases may exhibit what? What can it lead to if untreated?

A

classic leonine facies

can lead to hideous deformities if untreated

49
Q

What immune response leads to tuberculoid leprosy?

What immune response leads to lepromatous leprosy?

A

Th1

Th2

50
Q

Why is the lepromatous leprosy associated with poorer health outcomes?

A

Because B cell immunity is stimulated

51
Q

What happens to infectious state as treatment begins for leprosy?
How long does one need to be treated for?

A

Nearly non-infectious as soon as treatment starts.

Need to treat for a long time.

52
Q

What is the WHO operational definition for Leprosy?

A

Hypopigmented or reddish lesions with definite loss of sensation
involvement of peripheral nerves (definite thickening and loss of sensation)
Skin smear positive for acid fast bacilli

53
Q

How does leprosy spread?

A

Via respiratory secretions.

54
Q

What percentage of contacts develop leprosy?

A

only about 5%

55
Q

What is the incubation period of leprosy? Describe disease progression speed.

A

Long incubation period 1-30 years

Slow disease progression

56
Q

Although the distribution is mainly equatorial where else can we find leprosy?

A

Louisiana (Acadians), Texas and Hawaii

57
Q

What is the diagnostic method of choice for Leprosy?

A

skin biopsy

58
Q

What is an issue with growing M. leprae?

A

Cannot grow in culture yet

59
Q

What is the cause of fish tank granuloma?

Does it occur in salt or freshwater aquariums?

A

M. marinum

Both

60
Q

What is another word for the tuberculoid form of leprosy?

A

Paucibacillary

61
Q

What is another word for the lepromatous form of leprosy?

A

multibacilliary

Micro and Immunology (38 decks)

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