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Quiz 4 microbiology > Mycobacterium > Flashcards

Mycobacterium Flashcards

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Biology 101 flashcards
1
Q

What is the morphology of mycobacterium? Is it motile? Does it have a capsule or spore?

A

weakly gram positive
no capsule
no spore
nonmotile

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2
Q

Is mycobacterium an aerobe or anaerobe?

A

strict aerobe

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3
Q

What is a distinguishing feature of mycobacterium?

A

Stains acid-fast

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4
Q

What are the other acid fast organisms?

A

Nocardia, cryptosporidium parvum, isospora and cyclospora

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5
Q

What is unique about the mycobacterium cell wall?

A

It has a high lipid content

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6
Q

How fast does mycobacterium grow?

A

Very slowly. 12-20 hr doubling time and M leprae has never been cultured in vitro

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7
Q

Where does mycobacterium grow?

A

INTRAcellularly

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8
Q

Describe the structure of a granuloma

A

Multinucleate giant cell in the center, surrounded by epithelioid cells and T cells

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9
Q

What kind of granuloma does TB form?

A

Caseating granuloma

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10
Q

How is TB transmitted?

A

through respiratory droplets

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11
Q

When does TB disease develop?

A

When bacteria escape the body’s defenses

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12
Q

What is a ghon focus?

A

granulomatous inflammation of healed TB

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13
Q

What is a ghon complex?

A

Ghon focus with lymph node

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14
Q

What is a ranke complex?

A

calcified ghon complex

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15
Q

Hemptysis

A

Erosion of TB into blood vessels of lung

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16
Q

How do you detect TB?

A

Microscopy with acid fast/fluorescent stain
culture it
Test for mycolic acid or PCR

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17
Q

How would you demonstrate host response to TB?

A

X ray for granulomas
PPD
IGRA

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18
Q

What do you need to rule out if you observe an acid fast bacterium?

A

Other mycobacteria
nocardia
Actiniomyces
Other GI parasites too

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19
Q

How is leprosy transmitted?

A

Through nasal secretions. However, only 5% are susceptible to disease

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20
Q

What are the different forms of leprosy?

A

Tuberculoid (or paucibacillary)
Indeterminant
Lepromatous (multibacillary

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21
Q

Describe tuberculoid leprosy

A

Non-caseating granulomas in dermis.

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22
Q

How would you diagnose tuberculoid forms of leprosy?

A 
Few AFB
lepromin skin test is positive (delayed hypersensitivity is intact)
CD4+ T cells
Lots of TH1 cytokines
Macules
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23
Q

Describe lepromatous leprosy

A

Sheets of foamy macrophages in dermis

Large raised bulbous formations on skin

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24
Q

What diagnostic features would you see with lepromatous leprosy?

A 
Lots of foamy macrophages
No granulomas
AFB
Lepromin skin test negative (because poor ability to mobilize T cells)
CD8+ T cells
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25
Q

How do you treat M. Leprae?

A 
Multidrug regimen with 
dapsone
rifampin
clofazimine
For 2-3 years
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26
Q

How do you classify nontuberculous mycobacteria?

A

Runyon system.

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27
Q

Runyon I

A

slow growing, yellow-orange pigment

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28
Q

Runyon II

A

Slow growing, yellow-orange pigment in light or dark

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29
Q

Runyon III

A

Slow growing, no pigment

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30
Q

Runyon IV

A

rapid growers

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31
Q

how do you determine whether M. tuberculosis or nontuberculosis mycobaccteria have colonized the lung?

A

epidemiology
microscopic appearance
genetic probes

32
Q

How is NTM transmitted?

A

NOT from human to human. Can persist on equipments

33
Q

What are the symptoms of mycobacterium avium?

A

Many asymptomatic
cervical adenitits
Disseminated disease in AIDS
pulmonary disease but slower and less virulent than TB

34
Q

What are sources of MAC?

A 
house dust
soil
birds
farm animals (M intracellularae)
aerosolized water
35
Q

If you suspect TB, what other sources of pulmonary nodules must you rule out?

A

Metastasis
Autoimmune
Other infections

36
Q

how do you treat MAC?

A
  1. clarithromycoin

2. Azithromycin + ethambutol + rifampin

37
Q

What bacteria are responsible for Runyon IV rapid growers?

A

M. Abscessus
M chelonae
M fortuitum

38
Q

How do you treat M abscessus?

A

macrolides and linezolids. Hard to treat

39
Q

How do you treat M. fortuitum?

A

6-12 months with 2 drugs: macrolides, tetracyclines, quinolones, sulfa drugs

Surgery if all else fails

40
Q

What is cord factor?

A

Secreted by TB, it is correlated with virulence.

41
Q

Does TB secrete any exotoxins or endotoxins?

A

no

42
Q

What media does TB grow on?

A

lowenstein-Jensen medium

43
Q

Are serologic tests useful for TB?

A

No. Defense is mostly cell mediated.

44
Q

What are additional biochemical tests to identify TB?

A

Produces niacin

Catalase positive

45
Q

How do you treat active TB?

A

6-9 months with isoniazid, rifampin, pyrazinamide. In severe cases, add ethambutol

After 2 weeks of treatment, the pt should be noninfectious

46
Q

How do you treat latent TB?

A
  1. Isoniazid for 6-9 months
    OR
  2. Isoniazid + rifapentine for 3 months
47
Q

What are the atypical mycobacteria slow growers? (colonies in more than 7 days)

A
  1. mycobacterium avium-intracellulare
  2. mycobacterium kansasii
  3. mycobacterium marinum
  4. mycobacterium scrofulaceum
48
Q

What are the symptoms of mycobacterium kansasii?

A

tuberculosis like disease but is less antibiotic resistant than mycobacterium avium

49
Q

What are the symptoms of mycobacterium marinum?

A

skin lesion at the sight of abrasion acquired in swimming pool

50
Q

What are the symptom of mycobacterium scrofula?

A

scrofula=swollen, nontender cervical lymph nodes

51
Q

What is an important rapid grower of mycobacteria? What symptoms does it cause?

A

mycobacterium fortuitum-chelonei

Causes infection of prosthetic joints and indwelling catheters. Causes skin and soft tissue infections. Usually pretty resistant

52
Q

How do you treat tuberculoid forms of leprosy?

A

Dapsone plus rifampin

53
Q

How do you treat lepromatous forms of leprosy?

A

dapsone plus rifampin plus clofazimine

54
Q

Corynebacteria, a relative of mycobacteria, also has a high lipid content in the cell wall. Does it have acid-fast stain?

A

No. Because the mycolic acids are much shorter in length

55
Q

How long does it take to observe visible growth of TB on solid media?

A

3-8 weeks

56
Q

What bacteria can be found growing in armadillos and the foot pads of mice?

A

Mycobacterium leprae

57
Q

If you have an extensive history of amyloidosis, what complication are you prone to develop?

A

amyloidosis of liver, kidney, spleen

58
Q

Which type of leprosy leads to an abnormal immune response? What effects would you see?

A

Lepromatous leprosy:

  1. polyclonal hypergammaglobulinemia
  2. erythema nodosum leprosum
  3. antibody to M leprae
59
Q

Describe the pathological process of TB (specifically, the immune system’s response!)

A
  1. Macrophage ingests MTB
  2. Macrophage presents to CD4+ T cells
  3. T cells release IL-2 to self-stimulate
  4. T cell releases IFN-gamma to stimulate the macrophage
  5. Macrophage releases TNF-alpha to stimulate intracellular killing of MTB
60
Q

What variant allele confers increased susceptibility to MTB?

A

NRAMP1.

Different vitamin D receptors can have a protective effect

61
Q

Where can extrapulmonary tuberculosis occur?

A
  1. lymph
  2. skeletal
  3. GU
  4. CNS
62
Q

What is lymphatic tuberculosis called?

A

scrofula

63
Q

What is skeletal tuberculosis called?

A

Pott’s disease

64
Q

Why is there such a strong association between tuberculosis and HIV?

A

Because both require a CD4+ response to fight off disease

65
Q

How is multidrug resistance defined?

A

Resistance to at least INH and rifampin

66
Q

How is XDR-TB defined?

A

MDR plus resistance to fluororquinolones and injectable drug

67
Q

Is MTB intra or extracellular?

A

Can be either

68
Q

How do you treat MDR TB?

A

INH+Rifampin+pyrazinamide+fluoroquinolone

Treat for 9-12 months

69
Q

How do you treat someone with both TB and HIV infection?

A

Same but if response is poor, continue for 9 months or 4 months after a negative culture.

Make sure rifampin does not interfere with HIV drug protease inhibitors

70
Q

How do you know Tb treatment is working?

A

sputum cultures will be negative at 2 months.

71
Q

What is the ppd cut off for persons without risk of Tb?

A

15 mm

72
Q

What is the ppd cut off for persons who are recent immigrants from TB endemic areas, injection drug users, diabetic, or workers in high risk congregate settings?

A

10 mm

73
Q

What is the ppd cut off for people with HIV infection, organ transplant, are immunosuppressed, or have had known contact with someone with TB?

A

5 mm

74
Q

What are complications of the BCG vaccination?

A
  1. swelling
  2. abscess with adenopathy
  3. osteomyelitis
  4. disseminated BCG infection
75
Q

What are the important atypical mycobacteria? What organ does each infect?

A
  1. m marinum (soft tissue)
  2. m fortuitum (soft tissue)
  3. m avium (lung)
  4. m gordonae (rare lung)
76
Q

What is the most common NTM to cause human infection?

A

mycobacterium avium complex

77
Q

What are the symptoms of MAC?

A
  1. cervical adenitis
  2. pulmonary disease
  3. disseminated disease in AIDs

Quiz 4 microbiology (5 decks)

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