Microbiology - Tuberculosis/Non-TB mycobacteria - Greenblatt Flashcards Preview

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Flashcards in Microbiology - Tuberculosis/Non-TB mycobacteria - Greenblatt Deck (21)
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1
Q

What does the Lepromin PPD test?

A

Lepromin PPD tests anti-leprosy immunocompetence, NOT exposure
tuberculoid = PPD + (why it’s called tuberculoid) = Strong immune response
lepromatous = PPD - = no immune response

2
Q

T/F: The atypical mycobacteria are environmentally-acquired infections that cause neither TB nor leprosy.

A

True

3
Q

How do atypical mycobacterial infections present?

A

Atypical mycobacterial infection in an immunocompetent adult is usually cutaneous; scrofula in children;

immunosuppressed hosts may have systemic symptoms, particularly from M. kansasii or MAI/C

4
Q

What is the slowest growing human pathogen?

A

M. leprae
–no in vitro culture system,
slowest growing human pathogen,
prefers 30C to 37C

M. leprae has an extremely long incubation period, doesn’t transmit easily, only 5-10% of humans believed susceptible to disease

5
Q

T/F: Atypical mycobacterial infections may be difficult to treat once established; require multiple antibiotics

A

True

6
Q

How does M. leprae present (two forms)?

A

Hansen’s Disease (leprosy) presents on a range from:

Tuberculoid (paucibacillary, vigorous CMI both contains infection and damages nerves, PPD+) to Lepromatous (multibacillary, weak CMI, extensive cutaneous symptoms, PPD-)

Lepromatous easily tested by skin smear, biopsy, molecular probe, serology; PPD (-)

tuberculoid may be detected by biopsy or serology but sensitivity is low – physical exam, history, PPD (+)

7
Q

When treating patients with M. Leprae, what sequelae can they develop?

A

Lepromatous patients when treated may develop erythema nodosum;
severe cases can require immunomodulant treatment like thalidomide (teratogen!)

8
Q

How is leprosy treated?

A

Treat w/ 2yrs dapsone+rifampin

9
Q

Describe the hematogenous spread of TB

A

Hematogenous spread by intracellular infection of naieve macrophages; activated ones clear it,
CD8 cells kill infected macrophages and establish caseating granulomas in which infection is contained.
TNF-alpha also important for containment

10
Q

Eradication of TB seemed possible until?

A

Eradication seemed possible until AIDS

11
Q

What is the acid fast staining procedure for TB?

A

Mycobacteria gram stain poorly, are acid-fast, very slow-growing

Acid fast staining procedure uses carbolfuchsin stain, acid/alcohol decolorization, and methylene blue counterstain; acid-fast (+)s hold carbolfuchsin during decolorization

12
Q

Which strains of TB pose the greatest public health risk?

A

MDR and XDR strains are public health nightmares

13
Q

What is the main TB transmission method?

A

Transmission is almost always to lung by inhalation, to lymph nodes, kidney, bones, CNS by hematogenous spread, to GI by swallowing infected sputum

14
Q

How are TB infections combatted in the body?

A

Immunocompetent host raises strong CMI response, can hold infection latent for decades;

Immunosenescence or immunosuppression reactivates

15
Q

What are the extrapulmonary symptoms of TB?

A

Extrapulmonary:
scrofula (fine needle aspirate),
genitourinary (intravenous urography, urine culture),
CNS (MRI, spinal tap), skeletal (MRI, joint fluid culture),
GI (Xray, CT of abdomen),
miliary (chest Xray w/ bright spotlight, lateral Xray, chest CT)

16
Q

How should the incidence of TB be most effectively reduced?

A

The most helpful factors for reducing incidence of TB in a population are good diet & housing: latent cases are not contagious

17
Q

How is TB treated?

A

Begin Directly Observed Therapy with 4-plus-drug courses featuring isoniazid; isolate patient for first two weeks.

18
Q

What is the BCG vaccine?

A
for TB
BCG vaccine (live attenuated M. bovis) is used abroad, not cost-effective here, can create weak-moderate false positive TST
19
Q

How is TB diagnosed?

A

Acid fast staining procedure

Determine exposure by TST and/or IGRA, perform antibiotic resistance testing as soon as cultures grow (~2wks for cultures, another 3wks for resistance tests)

20
Q

What are the classic TB symptoms?

A

Classic pulmonary TB (75%): cough, weight loss (“consumption”), fever, night sweats, hemoptysis, and chest pain, check sputum and chest Xray

21
Q

Why should you culture TB from gastric secretions in children?

A

They are not strong enough to cough up sufficient sputum for testing.