Mycobacteria - Assignment Essays

Q: Defining characteristics Mycobacterium

Obligate aerobic filamentous “rods” Fastidious, slow growth - of note, fastidious means special nutrient or conditions required, complex nutritional requirements Acid-fastness

Q: What does a positive TB skin test indicate?

person has DTH adaptive immune response to MTB (at least 3-8 weeks ago) - no indication if latent or not

question

Defining characteristics Mycobacterium

answer

Obligate aerobic filamentous “rods”

Fastidious, slow growth

- of note, fastidious means special nutrient or conditions required, complex nutritional requirements

Acid-fastness

question

Do mycobacterium have exotoxin or endotoxin (LPS)?

answer

question

Mycobacteria are strict _________ and grow ____________

answer

aerobes

grow slowly

question

Besides the peptidoglycan layer, what else is special to the mycobacterium in terms of membrane components?

answer

mycolic acids and LAM

-contribute to Acid Fast stain

DONT NOT STAIN WITH GRAM STAIN!!!!

question

With mycobacterium tuberculosis, most people manifest symptoms through _________

answer

immune response

- infection can be cleared and become latent

Reactivation through chronic pneumonia

question

MTB is different from other mycobacterium because of....

answer

transmission from person to person

- often acquired from other people

question

MTB is a strict

answer

aerobe

question

"cording" is the typical growth pattern seen in

answer

MTB

question

Nonpigmented "corded" colonies of MTB will grow on which type of agars?

answer

albumin-based agars

- Lowenstein-Jensen media

question

MTB will produce _________ niacin test

answer

positive

question

What type of catalase activity do MTB have?

answer

weak

question

MTB is able to reduce __________.

answer

nitrate

question

Are MTB resistant to drying and disinfectants?

answer

yes

- BUT HEAT KILLS

question

Primary infection of MTB is spread through __________ which originate from _________ TB?

answer

aerosol droplets

Coming from person with active/infectious TB

- NOT LATENT

question

Droplet Nuclei

answer

transferred into healthy host (TB)

- contain 2-3 bacteria

- can float around for hours

- delivered all the way to alveoli

- taken up by resting macrophages

question

When resident tissue macrophages engulf MTB, they are unable to kill the intracellular bacteria. What activates them?

answer

Adaptive immune response (Th1)

- released cytokines activate macrophages to kill myobacteria

question

MTB can grow inside macrophages and are considered_________

answer

facultative pathogens

question

Th1 releases ___________

answer

IFN-y

question

What type of hypersensitivity is the result of MTB infection?

answer

DTH --> Type IV

question

What does a positive TB skin test indicate?

answer

person has DTH adaptive immune response to MTB (at least 3-8 weeks ago)

- no indication if latent or not

question

Ghon complex

answer

enlarged hilar lymph nodes results of primary TB

- develops over years

- evidence on x-ray

question

LTBI

answer

latent tuberculosis infection

question

In latent TB, how are mycobacteria contained

answer

in granuloma or tubercule

question

With reactivation TB, there will often times be ________ associated.

answer

cough

- dry

- eventually sputum devleops

question

Millet seed size granulomas is associated with which type of TB?

answer

miliary

question

Tuberculosis spondylitis

answer

arthritis like effects on spine/ destruction of vertebrae

- Pott disease

question

Which vaccination is used often in other countries to prevent childhood TB?

answer

Bacillus Calmette-Guerin

BCG

question

TB diagnosis

answer

¨Tuberculin skin test (TST) (Sometimes called PPD skin test “purified protein derivatives”) indicates exposure

¤Does not differentiate between active, latent, or eliminated infection

¤Chest x-ray may also be used

¨Interferon-g release assays (IGRAs): in vitro blood test; measures IFN-γ release in response to M. tuberculosis antigens; a sensitive, more specific alternative to the TST

¨Acid-fast staining and culture for active disease

¤Gold standard, requires 3-6 weeks; Löwenstein-Jensen agar

Culture required for antimicrobial susceptibility testing (CRITICAL for treatment)

¨Molecular techniques can be useful, but won’t eliminate the need for culture

question

What's the reservoir for Mycobacterium leprae?

answer

Armadillos

question

Are mycobacterium acid fast bacilli?

answer

yes

question

Can m. leprae be grown in culture?

answer

question

Paucibacillary Hansen's (tuberculoid)

answer

Strong cell-mediated immunity; weak/ normal humoral immunity

Not lethal (but should be treated)

Low infectivity*

question

Multibacillary Hansen’s (Lepromatus leprosy)

answer

Weak cell-mediated immunity; strong humoral immunity

Can be lethal

High infectivity*

question

Mycobacterium Avium Complex

answer

Not person to person

Environmental sources... example showerheads

¤Mycobacterium avium or Mycobacterium intracellulare

¤Opportunistic infection

question

Mycobacteria Avium complex are more so a worry for which type of patients?

answer

Immunocompromised

Hence opportunistic infections

question

MAC disseminated infections increase as __________ lowers

answer

CD4+ count

(less than 50 cells/uL)

1 of 36

question

Defining characteristics Mycobacterium

answer

Obligate aerobic filamentous “rods”

Fastidious, slow growth

- of note, fastidious means special nutrient or conditions required, complex nutritional requirements

Acid-fastness

question

Do mycobacterium have exotoxin or endotoxin (LPS)?

answer

question

Mycobacteria are strict _________ and grow ____________

answer

aerobes

grow slowly

question

Besides the peptidoglycan layer, what else is special to the mycobacterium in terms of membrane components?

answer

mycolic acids and LAM

-contribute to Acid Fast stain

DONT NOT STAIN WITH GRAM STAIN!!!!

question

With mycobacterium tuberculosis, most people manifest symptoms through _________

answer

immune response

- infection can be cleared and become latent

Reactivation through chronic pneumonia

question

MTB is different from other mycobacterium because of....

answer

transmission from person to person

- often acquired from other people

question

MTB is a strict

answer

aerobe

question

"cording" is the typical growth pattern seen in

answer

MTB

question

Nonpigmented "corded" colonies of MTB will grow on which type of agars?

answer

albumin-based agars

- Lowenstein-Jensen media

question

MTB will produce _________ niacin test

answer

positive

question

What type of catalase activity do MTB have?

answer

weak

question

MTB is able to reduce __________.

answer

nitrate

question

Are MTB resistant to drying and disinfectants?

answer

yes

- BUT HEAT KILLS

question

Primary infection of MTB is spread through __________ which originate from _________ TB?

answer

aerosol droplets

Coming from person with active/infectious TB

- NOT LATENT

question

Droplet Nuclei

answer

transferred into healthy host (TB)

- contain 2-3 bacteria

- can float around for hours

- delivered all the way to alveoli

- taken up by resting macrophages

question

When resident tissue macrophages engulf MTB, they are unable to kill the intracellular bacteria. What activates them?

answer

Adaptive immune response (Th1)

- released cytokines activate macrophages to kill myobacteria

question

MTB can grow inside macrophages and are considered_________

answer

facultative pathogens

question

Th1 releases ___________

answer

IFN-y

question

What type of hypersensitivity is the result of MTB infection?

answer

DTH --> Type IV

question

What does a positive TB skin test indicate?

answer

person has DTH adaptive immune response to MTB (at least 3-8 weeks ago)

- no indication if latent or not

question

Ghon complex

answer

enlarged hilar lymph nodes results of primary TB

- develops over years

- evidence on x-ray

question

LTBI

answer

latent tuberculosis infection

question

In latent TB, how are mycobacteria contained

answer

in granuloma or tubercule

question

With reactivation TB, there will often times be ________ associated.

answer

cough

- dry

- eventually sputum devleops

question

Millet seed size granulomas is associated with which type of TB?

answer

miliary

question

Tuberculosis spondylitis

answer

arthritis like effects on spine/ destruction of vertebrae

- Pott disease

question

Which vaccination is used often in other countries to prevent childhood TB?

answer

Bacillus Calmette-Guerin

BCG

question

TB diagnosis

answer

¨Tuberculin skin test (TST) (Sometimes called PPD skin test “purified protein derivatives”) indicates exposure

¤Does not differentiate between active, latent, or eliminated infection

¤Chest x-ray may also be used

¨Interferon-g release assays (IGRAs): in vitro blood test; measures IFN-γ release in response to M. tuberculosis antigens; a sensitive, more specific alternative to the TST

¨Acid-fast staining and culture for active disease

¤Gold standard, requires 3-6 weeks; Löwenstein-Jensen agar

Culture required for antimicrobial susceptibility testing (CRITICAL for treatment)

¨Molecular techniques can be useful, but won’t eliminate the need for culture

question

What's the reservoir for Mycobacterium leprae?

answer

Armadillos

question

Are mycobacterium acid fast bacilli?

answer

yes

question

Can m. leprae be grown in culture?

answer

question

Paucibacillary Hansen's (tuberculoid)

answer

Strong cell-mediated immunity; weak/ normal humoral immunity

Not lethal (but should be treated)

Low infectivity*

question

Multibacillary Hansen’s (Lepromatus leprosy)

answer

Weak cell-mediated immunity; strong humoral immunity

Can be lethal

High infectivity*

question

Mycobacterium Avium Complex

answer

Not person to person

Environmental sources... example showerheads

¤Mycobacterium avium or Mycobacterium intracellulare

¤Opportunistic infection

question

Mycobacteria Avium complex are more so a worry for which type of patients?

answer

Immunocompromised

Hence opportunistic infections

question

MAC disseminated infections increase as __________ lowers

answer

CD4+ count

(less than 50 cells/uL)

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