Chapter 1.15 Acid-Fast Bacteria Flashcards

1
Q

What are the 2 most common mycobacteria?

A

mycobacterium tuberculosis- causes tuberculosis

mycobacterium leprae- causes leprosy

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2
Q

What is the cell type of mycobacteria?

A

rods with lipid-laden cell walls
obligate aerobe
form clumped colonies during infection

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3
Q

What staining is used for mycobacteria?

A

acid-fast staining that holds a red stain

*a smear of sputum

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4
Q

What patients are not able to fight tuberculosis?

A

HIV/AIDS patients due to no cell-mediated immunity

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5
Q

What organ does mycobacteria most commonly infect?

A

lungs where oxygen is abundant (and it’s an aerobe so it likes that)

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6
Q

What class of lipids is only present in acid-fast organisms?

A

mycosides

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7
Q

How does mycobacterium tuberculosis interact with the immune system?

A
  1. facultative intracellular growth- first exposure causes local infiltration of neutrophils and macrophages but do not die
  2. cell mediated immunity- some macrophages break down bacteria and present to T-helper cells– cause macrophages to attack lung tissue causing necrosis
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8
Q

What is the necrosis of tuberculosis called?

A

caseous necrosis

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9
Q

What hypersensitivity is associated with tuberculosis?

A

delayed-type hypersensitivity

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10
Q

What helps determine if a person has been infected with Mycobacterium tuberculosis?

A

Purified Protein Derivative PPD

*doesn’t mean the patient has TB but it means they were exposed to it at some point

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11
Q

What does a positive PPD test look like?

A

red, raised and hard skin after 1-2 days of injection of PPD

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12
Q

What is the clinical manifestation of person with asymptomatic primary tuberculosis?

A

granulomas that turn into fibrosis, calcified scar tissue

tiny tubercles

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13
Q

How is primary tuberculosis transmitted?

A

aerosolized droplet nuclei from respiratory secretions of an adult with TB

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14
Q

What is a Ghon focus

A

calcified tubercle in the middle or lower lung zone in tuberculosis

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15
Q

What is the clinical presentation of a patient with symptomatic primary tuberculosis?

A

occurs in infants or elderly
mediastinal or hilar lymph nodes
can cause necrosis and form holes in lungs

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16
Q

What are the general manifestations of primary tuberculosis?

A

large caseous granulomas in lung

cavitary lesions that fill with fluid

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17
Q

When do most adult cases of tuberculosis occur?

A

after bacteria has been dormant for a while

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18
Q

What is the most common type of reactivation (secondary) tuberculosis?

A

pulmonary tuberculosis

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19
Q

What is the clinical presentation of a patient with pulmonary tuberculosis?

A

chronic low-grade fever, night sweats, weight loss, productive cough

20
Q

What is the appearance of lymph nodes in lymph node infection secondary tuberculosis?

A

cervical lymph nodes are swollen, mat together, and drain

*called scrofula

21
Q

What is the clinical presentation if the kidney is involved in secondary tuberculosis?

A

red and white blood in the urine
no bacteria seen in gram stain or none grow in culture
*called sterile pyuria

22
Q

What is the clinical presentation if the skeletal system is involved in secondary tuberculosis?

A

destruction of intervertebral discs and vertebral bodies

*called Pott’s disease

23
Q

What is the clinical presentation if the central nervous system is involved in secondary tuberculosis?

A

subacute meningitis

granulomas in the brain

24
Q

What is miliary tuberculosis?

A

tiny millet-seed-sized tubercles all over the body
chest film shows millet-seed pattern in lung
*occurs in children and elderly

25
What is the overall clinical picture of tuberculosis?
usually a chronic disease weight loss low-grade fever can involve lots of organ systems
26
What are 4 tests that can be done to diagnose tuberculosis?
1. PPD- indicates exposure in the past 2. Chest X-ray- shows granulomas, Ghon focus, Ghon complex, old scarring in upper lobes, active tuberculosis pneumonia 3. Sputum acid-fast stain and culture- if positive, means active pulmonary infection 4. Rapid Molecular Detection of MTB- sputum sample
27
What is the "Rule of Fives" for tuberculosis?
- Droplet nuclei are 5 micrometers and contain 5 Mycobacterium tuberculosis bacilli - Patient's infected with Mycobacterium tuberculosis have 5% risk of reactivation in the first 2 years and then 5% lifetime risk - Patients with "high five" HIV with have a 5 + 5% risk of reactivation per year
28
What is the disease caused by Mycobacterium leprae?
Leprosy (Hansen's Disease)
29
What is the cell type of mycobacterium leprae?
acid-fast rod
30
How is mycobacterium leprae transmitted?
when a person is exposed to respiratory secretions or skin lesions of an infected individual
31
What does the clinical presentation of leprosy depend on?
- bacteria grow better in cooler body temperatures close to the surface - severity depends on host's cell mediated immune response to bacilli
32
Where on the body does mycobacterium leprae damage?
skin, superficial nerves, eyes, nose, testes
33
What are the 2 general types of leprosy?
1. Lepromatous leprosy (LL) | 2. Tuberculoid leprosy (TL)
34
Why is lepromatous leprosy the severest form of leprosy?
because patients canNOT mount a cell-mediated immune response
35
What organs are involved in lepromatous leprosy?
skin, nerves, eyes, and testes
36
What is the clinical presentation of a patient with lepromatous leprosy?
skin lesions over body, facial skin is thickened (leonine facies), nasal cartilage destroyed (saddlenose deformity), intertesticular damage (infertility), anterior eye damage (blindness), peripheral nerve thickness (loss of sensation)
37
What occurs in tuberculoid leprosy (TL)?
Patient's with TL can mount a cell-mediated defense against the bacteria thus have milder symptoms
38
What is the clinical presentation of patient with tuberculoid leprosy?
localized superficial, unilateral skin and nerve involvement well-defined, hypopigmented, elevated blotches
39
What are the most frequently enlarged nerves in tuberculoid leprosy?
*nerves closest to skin | greater auricular, ulnar, posterior tibial, peroneal
40
What is the lepromin skin test?
measures the ability of the host to mount a delayed hypersensitivity reaction against antigens of Mycobacterium leprae
41
What is the difference between LL and TL patients when given the lepromin skin test?
TL patients- cell-mediated response, + test | LL patients- do not have cell-mediated response, - test
42
What are nontuberculous mycobacteria (NTM)?
organisms that are ubiquitous in the soil and water
43
When is nontuberculous mycobacteria most likely seen?
in AIDS patients with disseminated Mycobacterium avium-complex (MAC) disease
44
What is the clinical presentation of a patient with mycobacterium avium-complex disease?
unexplained fevers, weight loss, diarrhea, malaise, elevation of alkaline phosphatase
45
How is diagnosis of mycobacterium avium-complex confirmed?
growth in mycobacterial blood cultures