Tuberculosis (3)

Question 1

T/F: mycobacteria gram stain well

Answer 1

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

Question 2

Describe the process of gram staining:

Answer 2

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

Question 3

Do M. tuberculosis grow in vitro?

Answer 3

Yes, but very slowly

Question 4

Describe the important structural component of M. tuberculosis?

Answer 4

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)

Question 5

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

Answer 5

Humans

They are also pathogenic in guinea pigs

Question 6

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

Answer 6

True

Question 7

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

Answer 7

Chromosomes

Question 8

What is the infectious dose of M. tuberclosis?

Answer 8

<10 organisms can initiate infection…it is extremely infectious

Question 9

Describe the pathogenesis of tuberclosis?

Answer 9

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

Question 10

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

Answer 10

Lymph nodes

Kidney

Bones

Meninges

Question 11

How is the GI infected with TB?

Answer 11

Swallowing infectious sputum

Question 12

What type of immunity is needed for TB infections?

Answer 12

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

Question 13

What cytokine helps maintain TB latency?

Answer 13

TNF

Question 14

What is a Ghon complex?

Answer 14

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

Question 15

What are granulomatous lesions?

Answer 15

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

Question 16

What is a tubercule?

Answer 16

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

Question 17

What are the symptoms of classic active pulmonary TB?

Answer 17

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

Question 18

What does a CXR for active pulmonary TB show?

Answer 18

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

Noncalcified round infiltrates

Question 19

Symptoms of TB scrofula?

Answer 19

Cervical adenitis, usually unilateral

more commonly caused by TB in adults, not pediatric cases

Question 20

How is TB scrofula treated?

Answer 20

surgery

Question 21

Symptoms of GU TB?

Answer 21

Dysuria, hematuria, flank pain, “sterile pyuria”

Genital is usually secondary to renal

Most common site for extrapulmonary infection

Question 22

What are the symptoms of CNS TB?

Answer 22

CSF: decreased glucose, increased protein, pleocytosis

MRI is needed for Dx

Question 23

Symptoms of skeletal TB?

Answer 23

Arthritis in 1 joint

OR

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

Question 24

Symptoms of GI TB?

Answer 24

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

Question 25

Symptoms of milliary TB?

Answer 25

Many tiny noncalcified foci or infection

Question 26

Who is at greatest risk for milliary TB?

Answer 26

65 yo individuals with a primary infection

Question 27

What are the symptoms of TB meningitis?

Answer 27

+ brudzinski sign, nuchal rigidity, lethargy, cranial nerve palsies, altered DTRs

Question 28

Who is at greatest risk of TB meningitis?

Answer 28

Children <2 yo

Question 29

How is a PPD interpreted?

Answer 29

15mm= positive

10mm= positive if patient has risk factors

5mm= positive if has deficient CMI

Question 30

When will a PPD read positive if infected?

Answer 30

2-10 weeks after infection

Question 31

Can TB be cultured?

Answer 31

Yes, but grows very slowly….can take up to 2 weeks

Question 32

What are some Lab tests for the Dx of TB?

Answer 32

PCR for bacterial rRNA DNA (fast but not very sensitive)

Quanifuron gold–> TB blood tests detects latent infections and is specific for TB

Question 33

How is pumonary TB treated?

Answer 33

At least 6 months of isoniazid and rifampin and 2 months of pyrazinamide

Question 34

How are immunocompromised, disseminated disease and likely drug resistant cases treated?

Answer 34

9-12 months of:

Isoniazid, rifampin, pyrazinmide, ethambutol

Question 35

How are asymptomatic or latent infections treated?

Answer 35

6 months of isoniazid

Question 36

How are pediatric exposure treated?

Answer 36

6 months of prophylactic isoniazid

Question 37

How are MDR strains treated?

Answer 37

Cipro, amikacin ethionamide and cycloserine

Question 38

How are XDR strains treated?

Answer 38

CDC must be called for information

Question 39

Is there a TB vaccine?

Answer 39

Yes…the BCG vaccine (“bacillus calmette-Guerin”)

It prevents 7-% of symptomatic infections but does not prevent latent infections