Tuberculosis (3) Flashcards

1
Q

T/F: mycobacteria gram stain well

A

False…they gram stain poorly because of the mycolic acid in the peptidoglycan cell wall

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2
Q

Describe the process of gram staining:

A

1- Cover smear w/ carbofuchsin, steam over boiling water for 8 minutes
2- After slide has cooled, decolorize with acid- alcohol for 15-20 minutes

3- Counterstain with methylene blue for 30s

4- Rinse briefly with water to remobe excess methylene blue

5- Blot dry with bibulous paper and examine

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3
Q

Do M. tuberculosis grow in vitro?

A

Yes, but very slowly

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4
Q

Describe the important structural component of M. tuberculosis?

A

1- mycolic acid (gives it the acid fastness

2- Wax D (ajuvant)

3- Phosphatides (caseation necrosis)

4- Cord factor (virulence, microscopic serpentine appearance)

5- Phtiocerol dimycocerosaete (lung pathogenesis)

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5
Q

What is the natural host and reservoir for M. tuberculosis?

A

Humans

They are also pathogenic in guinea pigs

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6
Q

T/F: M. tuberculosis are intra- or extracellular obligate aerobes

A

True

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7
Q

How does M. tuberclosis keep its Ab resistance genes… on plasmid or chromosomes?

A

Chromosomes

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8
Q

What is the infectious dose of M. tuberclosis?

A

<10 organisms can initiate infection…it is extremely infectious

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9
Q

Describe the pathogenesis of tuberclosis?

A

1- Alveolar macrophages phagocytose the inhaled bacilli

2- Naive macrophages are unable to kill the intracelluar mycobacteria and the bacteria proliferate in the phagocytes and travel to extrapulmonary sites

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10
Q

What are the main sites that TB establises latency or active extrapulmary infections?

A

Lymph nodes

Kidney

Bones

Meninges

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11
Q

How is the GI infected with TB?

A

Swallowing infectious sputum

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12
Q

What type of immunity is needed for TB infections?

A

Cell Mediated immunity…it terminates the unimpeded growth of M. tuberclosis 2-3 weeks after initial infection

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13
Q

What cytokine helps maintain TB latency?

A

TNF

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14
Q

What is a Ghon complex?

A

Exudative lesion plus draining lymph nodes…they are usually found in the lower lobes of the lungs

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15
Q

What are granulomatous lesions?

A

Central area of infected Langhans giant cells surrounded by a zone of epitheloid cells

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16
Q

What is a tubercule?

A

Older granuloma surrounded by fibrous tissue, central caseation necrosis, heals by fibrosis and calcification

17
Q

What are the symptoms of classic active pulmonary TB?

A

Cough, weight loss, fever, night sweats, hemostysis, chest pain

18
Q

What does a CXR for active pulmonary TB show?

A

Cavity formation (indicates advanced infection and is associated with a high bacterial load

Noncalcified round infiltrates

19
Q

Symptoms of TB scrofula?

A

Cervical adenitis, usually unilateral

more commonly caused by TB in adults, not pediatric cases

20
Q

How is TB scrofula treated?

21
Q

Symptoms of GU TB?

A

Dysuria, hematuria, flank pain, “sterile pyuria”

Genital is usually secondary to renal

Most common site for extrapulmonary infection

22
Q

What are the symptoms of CNS TB?

A

CSF: decreased glucose, increased protein, pleocytosis

MRI is needed for Dx

23
Q

Symptoms of skeletal TB?

A

Arthritis in 1 joint

OR

Pott disease (spinal infection)–> back pain, stiffness, paralysis or lower extremities

24
Q

Symptoms of GI TB?

A

Abd pain, weight loss, anemia, fever w/ night sweats, obstruction and palpable mass

25
Symptoms of milliary TB?
Many tiny noncalcified foci or infection
26
Who is at greatest risk for milliary TB?
65 yo individuals with a primary infection
27
What are the symptoms of TB meningitis?
+ brudzinski sign, nuchal rigidity, lethargy, cranial nerve palsies, altered DTRs
28
Who is at greatest risk of TB meningitis?
Children <2 yo
29
How is a PPD interpreted?
15mm= positive 10mm= positive if patient has risk factors 5mm= positive if has deficient CMI
30
When will a PPD read positive if infected?
2-10 weeks after infection
31
Can TB be cultured?
Yes, but grows very slowly....can take up to 2 weeks
32
What are some Lab tests for the Dx of TB?
PCR for bacterial rRNA DNA (fast but not very sensitive) Quanifuron gold--> TB blood tests detects latent infections and is specific for TB
33
How is pumonary TB treated?
At least 6 months of isoniazid and rifampin and 2 months of pyrazinamide
34
How are immunocompromised, disseminated disease and likely drug resistant cases treated?
9-12 months of: Isoniazid, rifampin, pyrazinmide, ethambutol
35
How are asymptomatic or latent infections treated?
6 months of isoniazid
36
How are pediatric exposure treated?
6 months of prophylactic isoniazid
37
How are MDR strains treated?
Cipro, amikacin ethionamide and cycloserine
38
How are XDR strains treated?
CDC must be called for information
39
Is there a TB vaccine?
Yes...the BCG vaccine ("bacillus calmette-Guerin") It prevents 7-% of symptomatic infections but does not prevent latent infections