Mycobacterium

Question 0

What subspecies make up the mycobacterium tuberculosis complex?

Answer 0

M. Tuberculosis
M. Bovis
M. Bovis -BCG

Question 1

T/F: Mycobacterium are...
Gm +
Motile
Spore forming
encapsulated
cocci

Answer 1

T
F - non motile
F - DO NOT FORM SPORES
F - non-encapsulated
F - rods

Question 2

T/F: Mycobacterium are obligate aerobes

Answer 2

True…ish. All are except M. Bovis

Question 3

Mycobacteria are/are not acid fast

Answer 3

ARE

Question 4

What are mycolic acids and what is their significance

Answer 4

They are long-chain fatty acids found in mycobacterial cell walls. They provide mycobacteria with a high lipid content, and make 40 - 60 % of their dry weight. THEY ARE ABSENT IN MOST OTHER BACTERIA. THEY MAKE THINGS ACID FAST

Question 5

Mycobacteria grow slow/fast in culture

Answer 5

SLOW (~18 hours for TB)

** M. Leprae CANNOT BE CULTURED ** EVER. EVER.

Question 6

M. TB transmission

Answer 6

Human to Human, mostly acquired by inhalation of droplet nuclei, which can be suspended in air for very long periods of time.

Inhaled organisms ingested by macrophage - > transient bacteremia, granuloma formation in lung or other organs. Can become latent infection, or a symptomatic disease

Question 7

T/F: LTBI can be symptomatic

Answer 7

FALSE, latent TB infection is always asymptomatic.

Disease state is always symptomatic

Question 8

Ghon lesion, ghon complex, and Ranke complex are all:

Answer 8

Radiographic manifestation of a HEALED PRIMARY INNFECTION

Question 9

Extrapulmonary TB can occur in:

Answer 9

Lymphatics (scrofula)
Skeletal (potts disease)
GU
CNS

Question 10

TB often goes with HIV because

Answer 10

Critical role of CD4 cells in mycobacterial immunity, thus with HIV risk increases to progress from LTBI

Question 11

What is an advantage of the AFB test in diagnosing ACTIVE TB?
Disadvantages?

Answer 11

Advantageous is that it gives a same day result.
Disadvantages include; limited sensitivity (10^5 organisms needed) and limited specificity (patients with Non-tuberculosis mycobacterium - NTMs - will also test positive)

Question 12

TB treatment: what drugs are used for drug sensitive TB treatment and for how long?

Answer 12

4 “RIPE” drugs for 2 months - Rifampin, Isonazid, Pyrazinamide, Ethambutol

2 drugs for 4 months - Isonazid + Rifampin

Question 13

MDR TB is resistant to:

Answer 13

at least Isonazid + Rifampin.

These resistant strains have chromosome-mediated mechanisms caused by PRIOR Rx or INADEQUATE TREATMENT

Question 14

What type of reaction is the Tuberculin skin test used to diagnose Latent TB Infection (LTBI)? What is the reaction against?

Answer 14

It is a delayed type hypersensitivity reaction against ‘purified protein derivative’ - PPD

Question 15

T/F: The result of the TST are based on measurement of the diameter of erythema at the injection site

Answer 15

FALSE. Cutoffs based on diameter of INDURATION, not redness

common mistake made on interpretation…

Question 16

What are IRGAs used for

Answer 16

Interferon Gamma Release Assays are used as a blood assay to diagnose LTBI. It works because mononuclear cells from patients with TB infection produce IFN gamma in response to TB Ag.

Question 17

Treatment regimen for Latent TB infection:

Answer 17

Isonazid- 9 months (best, used for HIV +’s)
Others:
Isonazid 6 mo
Rifampin 4 mo
Rifapentine +Isonazid 1x weekly for 12 weeks

Question 18

T/F: M. Bovis causes TB in humans

Answer 18

True, but of a different form. M. Bovis produces TB in cows, but causes “gastrointestinal TB” in humans.

Question 19

What is M. Bovis BCG?

Answer 19

M. Bovis Bacille Calamette Guerin - this is an attenuated strain of M. bovis used as a live vaccine against TB in humans

Question 20

Efficacy of BCG vaccine

Answer 20

reduces childhood risk by 80% and all TB by 50%. Prevents other mycobacterial infection too. Provides protection from bacteremic related complications

Question 21

T/F: the BCG vaccine is given orally

Answer 21

FALSE, given as ID injection in TB endemic part of world

Question 22

Patient has PPD test and measures 13 mm induration. They have had the BCG vaccine. Should you be worried?

Answer 22

YES, patients with BCG vaccine WILL test positive BUT reactions would be under 10 mm.

Question 23

T/F: Patients (without TB) that have had BCG vaccine will test negative on IGRA

Answer 23

TRUE, IGRAs for LTBI are not affected by previous BCG vaccination

Question 24

Pathophysiology: Why does leprosy affect skin & mucous membranes?

Answer 24

Growth preference is at 27-33 degrees; thus it prefers cooler areas

Question 25

T/F: M. Leprae is primarily transmitted skin to skin

Answer 25

False, it is primarily aerosol respiratory transmission, but skin to skin is possible

Question 26

T/F: The typical incubation period for M. Leprae is 2 to 5 weeks

Answer 26

FALSE. 2 to 5 YEARS * Can range from just a few months up to 30 years

Question 27

The two forms of M. Leprae infection are:

Answer 27

Tuberculoid and Lepromatous

Question 28

A pathology with macrophage stuffed with M. Leprae and FEW granulomas would be characteristic of Tuberculoid/Lepromatous infection?

Answer 28

Lepromatous. Tuberculoid infection has a pathology of well-defined, non-caseating granulomas

Question 29

Tuberculoid leprosy is ____-bacillary; Lepromatous leprosy is _____-bacillary.

Answer 29

``` Tuberculoid = paucibacillary (few bacteria) Lepromatous = multibacillary (many) ```

Question 30

T/F: those who acquire leprosy often have a genetic predisposition

Answer 30

True

Question 31

The prognosis for Tuberculoid leprosy is good/poor | For Lepromatous leprosy it is good/poor

Answer 31

Good for Tuberculoid | Poor for Lepromatous

Question 32

T/F: an improved chemotherapy for leprosy includes Dapsone, Rifampin, and Clofazamine for 2-3 YEARS

Answer 32

TRUE. steroids may also be used for complications.

Question 33

The Runyon classification, based organism growth rate and color expression (in light vs. dark) is used to classify:

Answer 33

Nontuberculous Mycobacteria; there are many species...M. Avium most important

Question 34

T/F: Nontuberculus mycobacteria (NTM) can be pathogenic

Answer 34

True. They are pathogenic in immunocompromised or normal hosts. They are often seen as lab contaminants and must be amplified to distinguish from TB

Question 35

Mycobacterium avium complex is the most common NTM to cause human disease. Where is it found before transmission?

Answer 35

Widespread in water, soil, and birds

Question 36

T/F: M. Avium infections are becoming less common

Answer 36

False, INCIDENCE IS INCREASING

Question 37

``` Clinical syndrome of M. Avium in: Children - Lung disease patients - Normal people - AIDS patients - ```

Answer 37

Children - cervical adenitis or scrofula Chronic lung disease patients -> pulmonary disease Normal host - Pulmonary disease (especially old ladies) AIDS patient - Disseminated infection

Question 38

M. chelonae, M. fortuitum, and M. Abscessus are members of what mycobacterium group?

Answer 38

Rapidly Growing Mycobacterium (RGM) | INCIDENCE IS INCREASING!

Question 39

Some syndromes associated with rapidly growing mycobacterium are: (4)

Answer 39

Skin disease/ wound infection Prosthetic device infection Pulmonary disease (in lung disease pts) Disseminated infection (immunocomprimised)