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Micro Q3 > Mycobacterium > Flashcards

Mycobacterium Flashcards

0
Q

What subspecies make up the mycobacterium tuberculosis complex?

A

M. Tuberculosis
M. Bovis
M. Bovis -BCG

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1
Q 
T/F: Mycobacterium are...
Gm +
Motile
Spore forming
encapsulated
cocci
A 
T
F - non motile
F - DO NOT FORM SPORES
F - non-encapsulated
F - rods
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2
Q

T/F: Mycobacterium are obligate aerobes

A

True…ish. All are except M. Bovis

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3
Q

Mycobacteria are/are not acid fast

A

ARE

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4
Q

What are mycolic acids and what is their significance

A

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

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5
Q

Mycobacteria grow slow/fast in culture

A

SLOW (~18 hours for TB)

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

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6
Q

M. TB transmission

A

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

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7
Q

T/F: LTBI can be symptomatic

A

FALSE, latent TB infection is always asymptomatic.

Disease state is always symptomatic

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8
Q

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

A

Radiographic manifestation of a HEALED PRIMARY INNFECTION

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9
Q

Extrapulmonary TB can occur in:

A

Lymphatics (scrofula)
Skeletal (potts disease)
GU
CNS

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10
Q

TB often goes with HIV because

A

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

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11
Q

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

A

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)

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12
Q

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

A

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

2 drugs for 4 months - Isonazid + Rifampin

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13
Q

MDR TB is resistant to:

A

at least Isonazid + Rifampin.

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

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14
Q

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

A

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

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15
Q

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

A

FALSE. Cutoffs based on diameter of INDURATION, not redness

common mistake made on interpretation…

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16
Q

What are IRGAs used for

A

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.

17
Q

Treatment regimen for Latent TB infection:

A

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

18
Q

T/F: M. Bovis causes TB in humans

A

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

19
Q

What is M. Bovis BCG?

A

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

20
Q

Efficacy of BCG vaccine

A

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

21
Q

T/F: the BCG vaccine is given orally

A

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

22
Q

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

A

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

23
Q

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

A

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

24
Q

Pathophysiology: Why does leprosy affect skin & mucous membranes?

A

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

25
Q

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

A

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

26
Q

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

A

FALSE. 2 to 5 YEARS

  • Can range from just a few months up to 30 years
27
Q

The two forms of M. Leprae infection are:

A

Tuberculoid and Lepromatous

28
Q

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

A

Lepromatous.

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

29
Q

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

A 
Tuberculoid = paucibacillary (few bacteria)
Lepromatous = multibacillary (many)
30
Q

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

A

True

31
Q

The prognosis for Tuberculoid leprosy is good/poor

For Lepromatous leprosy it is good/poor

A

Good for Tuberculoid

Poor for Lepromatous

32
Q

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

A

TRUE.

steroids may also be used for complications.

33
Q

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

A

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

34
Q

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

A

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

35
Q

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

A

Widespread in water, soil, and birds

36
Q

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

A

False, INCIDENCE IS INCREASING

37
Q 
Clinical syndrome of M. Avium in:
Children -
Lung disease patients - 
Normal people - 
AIDS patients -
A

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

38
Q

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

A

Rapidly Growing Mycobacterium (RGM)

INCIDENCE IS INCREASING!

39
Q

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

A

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

Micro Q3 (5 decks)

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