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Host and Defense > Mycobacterium > Flashcards

Mycobacterium Flashcards

1
Q

What are mycobacteria?

A

Bacilli
Obligate aerobes
Cell Wall: High lipid content, mycolic acids

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2
Q

What is in the mycobacteria cell wall?

A

Mycelia acids
Lipoarabinomannan
“waxy coat”

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3
Q

What other name can mycobacteria be referred to?

A

Acid Fast Bacilli (AFB)

  • binds carbol fuchsin dye
  • acid fastness = resistance to decolorization by acid
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4
Q

Mycobacterium tuberculosis complex

A

majority of TB cases in humans

  • M. tuberculosis
  • M. africanum
  • M. bovis
  • M. bovis bacille calmette-guerin
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5
Q

Mycobacterium bovis

A

most commonly found in cattle

  • eating or drinking unpasteurized dairy products
  • direct contact with wound (bison, elk, deer)
  • can be transferred through respiratory (human - human)
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6
Q

Mycobacterium Bovis Bacille Calmette-Guerin

A

VACCINE for tuberculosis

  • infants and small children in other countries
  • cancer treatmemt?
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7
Q

Non tubercuolosis mycobacterium

A 
Found in soil, food, water and animals
AQUIRED BY INGESTION, ASPPIRATION, INOCCULATION
Slow growers
* Mycobacterium kansasii
* Mycobacterium avium
*Leading cause of NTM infections
Rapid growers (3-5 days)
Special growers (can't grow in culture)
* Mycobacterium leprae
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8
Q

How is TB spread?

A

Aerosols without visible primary lesion

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9
Q

Where is TB housed in primary infection>

A

base of lung close to pleura

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10
Q

What is the MTB virulence?

A

The ability to withstand the oxidative burst in phagocytosis by macrophages. Survive and replicate in macrophages.

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11
Q

MTB triggers…

A

T helper cell response
delayed type hypersensitivity
Inflammation – GRANULOMATOUS
Caseous necrosis in center

** if successful the infection is arrested.

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12
Q

Granuloma?

A

Masses or immune cells that form at site of infection

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13
Q

Caseous necrosis

A

morphological changes indicative of cell death caused by progressive enzymatic degradation
*cellular outline lost and tissue appears crumbly

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14
Q

If TB infection is arrested then….

A

caseous material is resorbed and is followed by fibrosis and dystrophic calcification

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15
Q

Ghon Complex

A

characteristic gross appearance with primary tuberculosis in the lung - yellow tan granuloma

visualization on CXR months to years later

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16
Q

In 90% of individuals TB infection remains latent but can become reactivated

A

.

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17
Q

Latent TB infection

A

people who ar infected but not sick

  • do not have symptoms
  • CAN NO spread TB to others
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18
Q

TB reactivation - SECONDARY TB

A

Principally in the LUNG - upper lobes

  • obligate anaerob
  • cavitation in upper lobes

Highest risk 1-2 years following exposure

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19
Q

Clinical features of TB

A 
Cough (chronic)
Sputum -- tissue necrosis
Dyspnea (SOB) -- pulmonary parenchyme
Fever -- inflammation
Weight loss -- inflammation
Night sweats

Caviatated CXR
Milliary CXR – small seeds over entire chest X-ray

20
Q

Risk factors

A 
Close contacts
Health care workers
Congregate settings
IV drug abusers
**HIV**
Recent immigrants to US
21
Q

Type IV hypersensitivity

A

DELAYED type hypersensitivity

  • takes 2-3 days to develop
  • not antibody mediated
22
Q

Mantoux tuberculin skin test (TST)

A

PPD - purified protein derivative

  • injected into inner surface of forearm - pale elevation of skin
  • skin test read 48 - 72 hrs after administration
  • reaction measured in MM OF INDURATION

This test tells us if the patient has latent TB not active TB. Delayed hypersensitvity.

23
Q

Induration of 5 or more mm

A

HIV
recent infection
organ transplants
immunosuppressed

24
Q

induration of 10 mm or more

A 
recent immigrants
drug users
high risk congregate settings
mycobacteriology lab personell
children <4 yrs old
25
Q

Induration of 15 mm or more

A

positive in any person with no known risk factors for TB

26
Q

Interferon - Gamma release Assays

A

Blood draws and tests for ACTIVE TB

  • infected persons cells will release interferon gamma when mixed with antigens
  • one visit, faster results
27
Q

Treating active TB requires ____ antibiotics and treating latent TB requires ___ antibiotics.

A

4

1

28
Q

How do you differentiate between active and latent TB?

A

Respiratory Samples - SPUTUM (3)
* Agar based culture (parmesan cheese)
* Nucleic acid amplification tests
* excess of 10,000 organisms per ml o sputum
Sterile tissue/body fluid – CSF, bone, pleural fluid
Urine – urinary tract disease

29
Q

TB can also cause…

A

pneumonia
pleural diffusions
kidney infections

30
Q

Does AFB stains differentiate between MTB and NTM?

A

NO! all mycobacterium have positive AFB stains

* Nucleic acid amplification tests - direct from sputum

31
Q

To detect Mycobacterium tuberculosis in a sputum sample _____ organisms per ml of sputum are needed to visualize the bacilli

A

10,000 with a 100x microscope

32
Q

Runyon I

A

PHOTOCHROMOGENS

  • slow growth
  • yellow orange pigment – only when exposed to light
  • M. kansasii
  • M. Marinum
33
Q

Runyon II

A

Scotochromogens

  • slow growth
  • pigmented in light or dark
  • M. scrofulaceum
34
Q

Runyon III

A

Nonchromogenic

  • slow growth
  • no pigment
  • M. avium
35
Q

Runyon IV

A

Rapid Growers

  • colonies in 5 days
  • no pigment
  • M. fortuitum
  • M. chelonae-abscessus
36
Q

M. Fortuitum

M. chelonae-abscessus

A

rapid growers (no pigmentation)
skin and soft tissue infection
lung infection

37
Q

M. kansussi

A 
Photochromogen
Chronic pulmonary disease
* resembles TB
* most infections SE, Midwest, Ca
* more common in males
38
Q

M. marinum

A

Photochromogen

  • grows best at cooler temps - extremities
  • traumatized skin in contact with water
39
Q

M. scrofulaceum

A

Scotochromogen

  • cervical lymphadenitis
  • diff diagnosis - MTB and MAC
  • environmental organism
40
Q

MAK complex (MAC)

A

Nonchromogen

Opportunistic infection - pulmonary infection

41
Q

Mycobacterium leprae

A

Hansen’s disease
Less infectious than TB - droplets
Symptoms can take as long as 20 yrs to appear (chronic)
Damage to skin, nerves, limbs, and eyes

42
Q

Symptoms of M. leprae

A

hypo pigmented or reddish patches on skin
Diminished sensation of loss of sensation with skin patches
Parasthesia - hands and feet
painless wounds
lumps or swelling on earlobes or face

43
Q

Lepromatous leprosy

A

raised or noduluar lesions on all parts of body
paresthesia with tender palpable peripheral nerve
low cellular immunity
sheets of foamy macrophages in the dermis - mutlibacillary

44
Q

Tuberculoid leprosy

A

central hypo pigmentation and hypoesthesia
high cellular immunity
granulomatous inflammation
rare acid fast bacilli in the tissues - paucibacillary

45
Q

Transmission of:

  • MTB and Leprosy
  • NTM
A

person to person

environmental exposures

Host and Defense (5 decks)

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