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Quiz 4 microbiology > Mycobacterium > Flashcards

Mycobacterium 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
How do you treat M. Leprae?
``` Multidrug regimen with dapsone rifampin clofazimine For 2-3 years ```
26
How do you classify nontuberculous mycobacteria?
Runyon system.
27
Runyon I
slow growing, yellow-orange pigment
28
Runyon II
Slow growing, yellow-orange pigment in light or dark
29
Runyon III
Slow growing, no pigment
30
Runyon IV
rapid growers
31
how do you determine whether M. tuberculosis or nontuberculosis mycobaccteria have colonized the lung?
epidemiology microscopic appearance genetic probes
32
How is NTM transmitted?
NOT from human to human. Can persist on equipments
33
What are the symptoms of mycobacterium avium?
Many asymptomatic cervical adenitits Disseminated disease in AIDS pulmonary disease but slower and less virulent than TB
34
What are sources of MAC?
``` house dust soil birds farm animals (M intracellularae) aerosolized water ```
35
If you suspect TB, what other sources of pulmonary nodules must you rule out?
Metastasis Autoimmune Other infections
36
how do you treat MAC?
1. clarithromycoin | 2. Azithromycin + ethambutol + rifampin
37
What bacteria are responsible for Runyon IV rapid growers?
M. Abscessus M chelonae M fortuitum
38
How do you treat M abscessus?
macrolides and linezolids. Hard to treat
39
How do you treat M. fortuitum?
6-12 months with 2 drugs: macrolides, tetracyclines, quinolones, sulfa drugs Surgery if all else fails
40
What is cord factor?
Secreted by TB, it is correlated with virulence.
41
Does TB secrete any exotoxins or endotoxins?
no
42
What media does TB grow on?
lowenstein-Jensen medium
43
Are serologic tests useful for TB?
No. Defense is mostly cell mediated.
44
What are additional biochemical tests to identify TB?
Produces niacin | Catalase positive
45
How do you treat active TB?
6-9 months with isoniazid, rifampin, pyrazinamide. In severe cases, add ethambutol After 2 weeks of treatment, the pt should be noninfectious
46
How do you treat latent TB?
1. Isoniazid for 6-9 months OR 2. Isoniazid + rifapentine for 3 months
47
What are the atypical mycobacteria slow growers? (colonies in more than 7 days)
1. mycobacterium avium-intracellulare 2. mycobacterium kansasii 3. mycobacterium marinum 4. mycobacterium scrofulaceum
48
What are the symptoms of mycobacterium kansasii?
tuberculosis like disease but is less antibiotic resistant than mycobacterium avium
49
What are the symptoms of mycobacterium marinum?
skin lesion at the sight of abrasion acquired in swimming pool
50
What are the symptom of mycobacterium scrofula?
scrofula=swollen, nontender cervical lymph nodes
51
What is an important rapid grower of mycobacteria? What symptoms does it cause?
mycobacterium fortuitum-chelonei Causes infection of prosthetic joints and indwelling catheters. Causes skin and soft tissue infections. Usually pretty resistant
52
How do you treat tuberculoid forms of leprosy?
Dapsone plus rifampin
53
How do you treat lepromatous forms of leprosy?
dapsone plus rifampin plus clofazimine
54
Corynebacteria, a relative of mycobacteria, also has a high lipid content in the cell wall. Does it have acid-fast stain?
No. Because the mycolic acids are much shorter in length
55
How long does it take to observe visible growth of TB on solid media?
3-8 weeks
56
What bacteria can be found growing in armadillos and the foot pads of mice?
Mycobacterium leprae
57
If you have an extensive history of amyloidosis, what complication are you prone to develop?
amyloidosis of liver, kidney, spleen
58
Which type of leprosy leads to an abnormal immune response? What effects would you see?
Lepromatous leprosy: 1. polyclonal hypergammaglobulinemia 2. erythema nodosum leprosum 3. antibody to M leprae
59
Describe the pathological process of TB (specifically, the immune system's response!)
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
What variant allele confers increased susceptibility to MTB?
NRAMP1. | Different vitamin D receptors can have a protective effect
61
Where can extrapulmonary tuberculosis occur?
1. lymph 2. skeletal 3. GU 4. CNS
62
What is lymphatic tuberculosis called?
scrofula
63
What is skeletal tuberculosis called?
Pott's disease
64
Why is there such a strong association between tuberculosis and HIV?
Because both require a CD4+ response to fight off disease
65
How is multidrug resistance defined?
Resistance to at least INH and rifampin
66
How is XDR-TB defined?
MDR plus resistance to fluororquinolones and injectable drug
67
Is MTB intra or extracellular?
Can be either
68
How do you treat MDR TB?
INH+Rifampin+pyrazinamide+fluoroquinolone | Treat for 9-12 months
69
How do you treat someone with both TB and HIV infection?
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
How do you know Tb treatment is working?
sputum cultures will be negative at 2 months.
71
What is the ppd cut off for persons without risk of Tb?
15 mm
72
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?
10 mm
73
What is the ppd cut off for people with HIV infection, organ transplant, are immunosuppressed, or have had known contact with someone with TB?
5 mm
74
What are complications of the BCG vaccination?
1. swelling 2. abscess with adenopathy 3. osteomyelitis 4. disseminated BCG infection
75
What are the important atypical mycobacteria? What organ does each infect?
1. m marinum (soft tissue) 2. m fortuitum (soft tissue) 3. m avium (lung) 4. m gordonae (rare lung)
76
What is the most common NTM to cause human infection?
mycobacterium avium complex
77
What are the symptoms of MAC?
1. cervical adenitis 2. pulmonary disease 3. disseminated disease in AIDs

Quiz 4 microbiology (5 decks)

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