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Micro Quiz 4 Final > 24a Mycobacterium TB from Lecture then Leprosy > Flashcards

24a Mycobacterium TB from Lecture then Leprosy Flashcards

1
Q

What are the four types of Mycobacterial classifications?

A 
Mycobacterium leprae (leprosy)
Mycobacterium tuberculosis (human TB)
Mycobacterium bovis (bovine and human TB)
Non-tuberculous mycobacteria (some human pathogens)
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2
Q

What M. tuberculosis Complex (5)?
These are different than, but overlapping the “types” of TB.
Essentially, it is a mix of Mycobacterium that are sometimes found together in a diseased patient.

A 
M. tuberculosis
M. africanum
M. bovis
M. bovis-BCG vaccine strain
M. cannetti
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3
Q 
What are the general properties of mycobacteria?
Gram status?
Shape?
Capsule status?
Motility?
Spore status?
O2 status?
Intra or Extra cellular status?
Ease of producing culture?
A

Gram + non-encapsulated rod
Not motile
Non-spore forming
Obligate aerobe (except one species: M. bovis)
Intracellular
Fastidious (needs special medium to grow) and grows very slowly

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4
Q

What is the only Mycobacterium that is NOT and OBLIGATE AEROBE?

A

M. bovis

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5
Q

Describe the significance of “Acid-Fast”?

A

Code word: Acid fast usually = mycobacterium
Red phenol dye (arylmethane) complexes with MYCOLIC ACIDS and cannot be washed out with acid alcohol

Note: other species are also weakly acid fast

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6
Q

In addition to Mycobacterium, what other bacteria are also acid fast?

A

Nocardia (respiratory)
Actinomycoses (respiratory)

Cryptosporidium parvum (GI)
Isospora (GI)
Cyclospora cysts
Sarcocystis (GI)

However, if it is a board question that says “acid fast” think Mycobacterium TB

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7
Q

What are the two stains that use acid fast?

A

Ziehl-Neelsen stain

Kinyoun stain

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8
Q

What parasites are acid fast?

A

Mycobacterium are strongly acid fast with a thick wall of MYCOLIC ACID

Nocardia, Actinomycoses, Cryptosporidium parvum, Isospora, Cyclospora cysts, Sarcocystis are weakly acid fast with a thinner wall of MYCOLIC ACID

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9
Q

What is a short cut to acid fast observation?

A

Flourscent dye makes Mycobacteria glow and is easier to see.

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10
Q

What is unique about Mycobacterial cell walls?

A

Very thick layer containing mycolic acid (binds to red phenol dye in acid fast test)
The cell wall is so thick Mycobacterium are described as “wax ball” enclosing DNA

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11
Q

What is the “cord factor” of Mycobacterium tuberculosis?

A

Two MYCOLIC ACIDS attached to TREHALOSE

Virulence factor

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12
Q

What is “cording” with regard to Mycobacterium?

A

Phenomenon of culture growth.
Mycobacterium grow in a frayed cord-like picture.
This is due to the thick cell wall of Mycolic acids and Trehalose.

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13
Q

Describe the slow growth of Mycobacterium?

A

Very thick wall leads to slow growth

eg Generation time is 20 hours

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14
Q

Which Mycobacterium cannot be grown on artificial medium?

A

M. Leprae (leprosy)

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15
Q

Detail: Why should we be wary of assuming TB if we see granulomas in the lungs?

A

Granulomas can also be due to:

Infections: mycobacteria, histoplasmosis, cat scratch, cryptococcosis, coccidio, blasto

Non-infectious: sarcoid, Crohn’s, berylliosis, Wegener’s granulomatosis, Churg-Strauss, rheumatoid, particulates

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16
Q

What is the significance and uniqueness of respiratory transmission of TB?

A

“One droplet nuclei”
A single organism can cause disease
Organisms can live in a air-floating respiratory droplet for up to 8 hours.
Droplets are very small and can pass through surgical mask. Need a special mask.
Very expensive to filter air of hospital patients.
30% infection rate in close contact!

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17
Q

Detail: Mycobacterium leprae
Prevalence in US: 1000 cases per year, mostly imported
Prevalence in world: 20 million!

A

Detail:
Prevalence in US: 1000 cases per year, mostly imported
Prevalence in world: 20 million!

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18
Q

What are the 4 possible outcomes when a patient inhales TB?

These are four terms to know.

A

Eliminated
Multiply and cause disease = primary TB
Become dormant = latent TB infection (LTBI) ASYMPTOMATIC
LTBI converts to active TB = reactivation TB disease

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19
Q

What are the symptoms of pulmonary TB?

A

Cough
Weightloss
Drenching night sweats

20
Q

What is a Ghon focus?
What is a Ghon complex?
What is a Ranke complex?

A

Ghon focus: granulomatous inflammation of healed primary TB in lung parenchyma
Ghon complex: Ghon focus with lymph node
Ranke complex: calcified Ghon complex

21
Q

What is Caseous Necrosis vs Caseous Granuloma?

A

Macro veiw vs histological view

22
Q

What is Rasmussen’s Aneurysm?

A

a pulmonary artery aneurysm adjacent or within a tuberculous cavity. It occurs in up to 5% of patients with such lesions. It may lead to rupture and haemorrhage. Patients may cough up blood till death.

23
Q

Distinguishing infection from diesease…
What are the risks of a patient with LTBI developing TB?
Lifetime?
Per year?
What if they have HIV also?

A

Persons with LTBI have high risk of progressing to TB disease, esp in first 2 years
Lifetime risk of LTBI to disease is 10%
TB and HIV synergistic: annual risk of disease 10%

24
Q

What symptoms occur with Latent TB?

Is LTBI infectious?

A

NONE. Trick question.

NOT infectious if there are no symptoms. The infection is LATENT and cannot be spread.

25
Q

What are steps to Dx TB?

A

1) See it: microscopy with acid fast or fluorescent stain
2) Grow it: solid or liquid culture
3) Find bits of its: Mycolic acids (e.g., LAM urine test) and/or Genetic material (e.g., PCR)
4) Demonstrate host response to it:
Typical pathology: Chest Xray? Granulomas?
Immune response to PPD or IGRAs

26
Q

What determines the decision to intiate treatment for TB?

A 
Epidemiology
Signs compatible with TB
AFB smear status
Seriously ill (e.g., miliary TB)
High risk of transmission

Most of the world just uses AFB smear.

27
Q

What is M. bovis?

What is BCG?

A

M. bovis is a species. They tried to use it as a vaccine. Total Fail. People were infected with M. bovis.

BCG is live attenuated M. bovis that is a modestly successful vaccine.

28
Q

Who is the BCG vaccine used for?

Who does it not protect?

A

BCG is effective at preventing fatal pediatric TB
Not effective at preventing adult pulmonary TB.

Note: most of the world has had this vaccine.

29
Q

What are the hosts for Mycobacterium leprae?

A

Humans and armadillos

Note: M. leprae is an obligate pathogen. Cannot survive without host.

30
Q

What is the prefered temperature for Mycobacterium leprae?

On what tissues do they normally grow?

A

27 to 33 C (cooler)

Skin, nose, mucous membranes of upper respiratory tract

31
Q 
Epidemiology of Mycobacterium leprae...
Transmission?
What age is susceptible?
Incubation period?
How infectious?
A

Respiratory transmission nasal secretions (snot), but possibly skin to skin
Children are more susceptible than adults
2-5 years incubation period!
VERY LOW INFECTIOUS LEVEL: only 5% of people can be infected. Each infected person is rended non-infectious within a few days of treatment.

32
Q

What is the official name for Leprosy?

A

Hansen’s Disease (HD)

33
Q

What are tissues affected by Mycobacterium leprae?

A

Skin

Amyloidosis can occur in kidney, liver, and spleen

34
Q

What are the three forms of Mycobacterium leprae?

A

Lepromatous (bad) aka MULTIBACILLARY
Intermediate
Tuberculoid (better) aka PAUCIBACILLARY

35
Q

What is the genesis of these forms of Mycobacterium leprae…
Lepromatous
Tuberculoid

A

L: Macrophage or histiocyte takes up bacilli

T: Similar to TB; chronic granulomatous lesions form as a proliferative reaction to bacilli; epithelioid and giant cells are present without caseation

36
Q

Detail for Mycobacterium leprae…
L forms a “lepra” cell, which is a macrophage stuffed with bacilli
T forms a microscopic tubercules

A

.

37
Q

What are the skin lesions like for these forms of Mycobacterium leprae…
Lepramatous?
Tuberculoid?

A

L: PAPULE, raised brown wheal-like mosiquito bite; thickening of the skin; ulceration is possible.

T: MACULE, may be hypo-pigmented or erythematous; Anaesthesia due to nerve toxicity; confluent lesions give rise to plaques

38
Q

What are the number of Mycobacterium leprae found in…
Lepramotous infections?
Tuberculoid infections?

A

L: LOTS per gram of infected skin

T: FEW towards the center of the lesion

39
Q

What are the effects of the LEPROMIN SKIN TEST in Mycobacterium leprae…
Lepramotous?
Tuberculoid?

A

L: lepromin skin test NEGATIVE

T: lepromin skin test POSTITIVE

40
Q

What about the immune response in general for lepramotous vs tuberculoid Mycobacterium leprae?
Ability to mobilize T cells?
What type of T cells?
IgG response

A

L: LOW IMMUNE RESPONSE, LOW ability to mobilize T cells, SUPRESSOR T CELLS present, HIGH POLYCLONAL IgG levels

T: GOOD IMMUNE RESPONSE, GOOD delayed hypersensitivity is intact, helper T cells present, NORMAL IgG levels

Note: in both cases, there is a lack of host killing intracellular bacteria

41
Q

What are some physical Dx features of Leprosy aka Hensen’s disease?

A

Loss of eyebrows
Nostrils deformed
Ear lobe thick
“Lion face”

42
Q

Note: Hensen’s disease can can infect nerves and make them swollen and insensitive.

A

.

43
Q

What is Erythema Nodosum Leprosum (ENL)?

Which form of Mycobacterium leprae causes this?

A

IgGs form immune complexes that deposit AMYLOID in the kidneys, liver, and spleen.
Lepramotous causes
Complication of the hyper polyclongal IgGs

44
Q

What is the Tx for Erythema Nodosum Leprosum (ENL)?

A

Immunosuppression

46
Q

What is the Dx of Mycobacterium leprae?

A

Difficult.

Based on gross appearance and location of lesions, histology, Acid-fast stains from lesions

47
Q

That is the Tx for Mycobacterium leprae?

A

Multi-Drug Treatment MDT

Dapsone (sulfonamide-like)
Rifampin (cidal)
Clofazimine (can cause blue skin)
ENL complication? Tx with immune suppression

48
Q

Control measures and prevention for Mycobacterium leprae?

A

List of household contacts for 5 years!

BCG aka a TB vaccine offers some protection

Micro Quiz 4 Final (10 decks)

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