L22_Mycobacteria

Question 1

What bacterium causes Tuberculosis?

Answer 1

Mycobacterium Tuberculosis

Question 2

At one point eradication of M. tuberculosis seemed possible, what was this and what happened that stymied this hope?

Answer 2

It was thought possible because humans were the sole reservoir for the bug, and if you killed it in humans it would have nowhere to go. The AIDS epidemic fucked it all up

Question 3

What particular strains are public nightmares?

Answer 3

MDR and XDR strains

Question 4

How do mycobacteria stain?

Answer 4

They gram stain poorly, they are acid-fast (pink/red)

Question 5

Describe the rate of growth of mycobacteria.

Answer 5

Very slow, this causes them to be inherently hard to treat with antibiotics

Question 6

Describe the acid fast staining process

Answer 6

1 carbolfuschin stain
2 acid/alcohol decolorization
3 methylene blue counterstain
Acid fast bacteria retain carbolfuschin color during decolorization Acid fast (RED) Non- Acid Fast (BLUE)

Question 7

Describe the transmission of M. tuberculosis and its spread throughout the body.

Answer 7

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

Question 8

Describe the course of the disease and CMI response in most immunocompetent individuals.

Answer 8

Immunocompetent host raises strong CMI response, can hol dinfection latent for decades; immunosenescence or - suppression can reactivate and become infectious again if still in lung. Most immunocompetent hosts can clear the disease successfully and contain it.

Question 9

Describe TNF-alpha role in M. Tuberculosis

Answer 9

TNF is important for retaining latency. If TNF antagonists are administered to a carrying host, they may reactivate a caseating granuloma.

Question 10

Describe the ways in which M. tuberculosis can spread hematogenously.

Answer 10

Free bacteria can travel in the blood or some can use naive macrophages as trojan horses.

Question 11

Describe the course of action once the body elicits an immunogenic response.

Answer 11

If patient is healthy after a few days active immunity will come online, infected macrophages (killed by CD8 cells) and free floating bacteria will be purged. What will remain are sites where the body could not completely eradicate the infection and will be walled off by granulomas, if there is a high pO2 the Tb can remain,
-if granulomas remain inactive they will gradually calcify and may remain quiescent for decades, however if at any point patient becomes immunocompromised these sites can be reactivated at any of these sites

Question 12

What are the symptoms of classic pulmonary TB (75%)? What should you do if you witness these in a patient?

Answer 12

Cough, weight loss (consumption), fever, night sweats, hemoptysis, and chest pain. take chest X-ray and check sputum.

Question 13

Extrapulmonary manifestations of M. tuberculosis are usually reactivations, name some of the common sites and any specific nomenclature.

Answer 13

Neck- Scrofula (in kids scrofulas are usually atypical mycobacteria)
genitourinary, CNS (meningitis or abscess), skeletal (long bone or spine[pott’s disease]), miliary, GI(rare)

Question 14

What two specific manifestations of tuberculosis should be watched for in immunosupressed individuals or children?

Answer 14

Miliary and meningitis

Question 15

What tests are there for Tb and what do the tests tell you?

Answer 15

you can determine EXPOSURE only by TST and/or IGRA (not for current disease)

Question 16

What is so difficult about the culture of M. Tuberculosis

Answer 16

It grows extremely slow. it takes 2 weeks for cultures and another 3 weeks for resistance tests

Question 17

What therapies are there for Tb?

Answer 17

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

Question 18

Is there a vaccine for Tb?

Answer 18

BCG vaccine is a live attenuated M. bovis. it is not cost effect. It doesnt prevent infection but helps ramp up immune response and force latency earlier. will create a weak to moderate false positive TST

Question 19

What are the most helpful factors in reducing incidence of Tb in a population?

Answer 19

good diet and housing: latent cases are not contagious.

Question 20

How are atypical mycobacteria acquired? Do they cause Tb or Leprosy?

Answer 20

environmentally. they do not cause Tb or Leprosy

Question 21

What is the typical infection route for atypical mycobacteria in an immunocompetent adult? children?

Answer 21

adult- cutaneous

children- scrofula

Question 22

Immunosupressed host may have systemic symptoms from atypical mycobacteria particularly from which two species?

Answer 22

M. Kansasii and MAI/C (M. Avium/ M. intracellulare)

Question 23

Describe the ease of treatment of atypical mycobacteria.

Answer 23

Infections may be difficult to treat once established; require multiple antibiotics

Question 24

Describe growth of M. Leprae, culture system, speed, etc.

Answer 24

It has no in vitro growth system, slowest growing human pathogen, prefers 30C

Question 25

What percentage of humans are susceptible to M. Leprae. How easily is it transmitted? What is its incubation period?

Answer 25

5-10%, doesn’t transmit easily, extremely long incubation period

Question 26

Leprosy is also known as?

Answer 26

Hansens Disease

Question 27

Describe the range in which leprosy presents, what are the two extremes?

Answer 27

Tuberculoid (paucibacillary, vigorous CMI both contains infection and damages nerves PPD+)
Lepromatus (Multibacilary, weak CMI, extensive cutaneous symptoms, PPD-, nerve damage casue by overgrowth of bacteria)

Question 28

What does the lepromin PPD test indicate?

Answer 28

It tests for anti-leprosy immunocompetence, NOT exposure

Question 29

How do you treat leprosy?

Answer 29

2 yrs of dapsone+rifampin

Question 30

What does M. Kansasii cause? what is it treated with?

Answer 30

Tb like symptoms treated with the same drugs

Question 31

What does MAI/C cause?

Answer 31

pulmonary disease that is very difficult to distinguish from TB. They are highly drug resistant.

Question 32

what does IGRA stand for?

Answer 32

Interferon gamma release assay

Question 33

What is the correct immune response to M. Leprae?

Answer 33

TH1 response