Chapter 1.15 Acid-Fast Bacteria

Question 1

What are the 2 most common mycobacteria?

Answer 1

mycobacterium tuberculosis- causes tuberculosis

mycobacterium leprae- causes leprosy

Question 2

What is the cell type of mycobacteria?

Answer 2

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

Question 3

What staining is used for mycobacteria?

Answer 3

acid-fast staining that holds a red stain

*a smear of sputum

Question 4

What patients are not able to fight tuberculosis?

Answer 4

HIV/AIDS patients due to no cell-mediated immunity

Question 5

What organ does mycobacteria most commonly infect?

Answer 5

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

Question 6

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

Answer 6

mycosides

Question 7

How does mycobacterium tuberculosis interact with the immune system?

Answer 7

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

Question 8

What is the necrosis of tuberculosis called?

Answer 8

caseous necrosis

Question 9

What hypersensitivity is associated with tuberculosis?

Answer 9

delayed-type hypersensitivity

Question 10

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

Answer 10

Purified Protein Derivative PPD

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

Question 11

What does a positive PPD test look like?

Answer 11

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

Question 12

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

Answer 12

granulomas that turn into fibrosis, calcified scar tissue

tiny tubercles

Question 13

How is primary tuberculosis transmitted?

Answer 13

aerosolized droplet nuclei from respiratory secretions of an adult with TB

Question 14

What is a Ghon focus

Answer 14

calcified tubercle in the middle or lower lung zone in tuberculosis

Question 15

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

Answer 15

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

Question 16

What are the general manifestations of primary tuberculosis?

Answer 16

large caseous granulomas in lung

cavitary lesions that fill with fluid

Question 17

When do most adult cases of tuberculosis occur?

Answer 17

after bacteria has been dormant for a while

Question 18

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

Answer 18

pulmonary tuberculosis

Question 19

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

Answer 19

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

Question 20

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

Answer 20

cervical lymph nodes are swollen, mat together, and drain

*called scrofula

Question 21

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

Answer 21

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

Question 22

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

Answer 22

destruction of intervertebral discs and vertebral bodies

*called Pott’s disease

Question 23

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

Answer 23

subacute meningitis

granulomas in the brain

Question 24

What is miliary tuberculosis?

Answer 24

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

Question 25

What is the overall clinical picture of tuberculosis?

Answer 25

usually a chronic disease
weight loss
low-grade fever
can involve lots of organ systems

Question 26

What are 4 tests that can be done to diagnose tuberculosis?

Answer 26

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

Question 27

What is the “Rule of Fives” for tuberculosis?

Answer 27

• 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

Question 28

What is the disease caused by Mycobacterium leprae?

Answer 28

Leprosy (Hansen’s Disease)

Question 29

What is the cell type of mycobacterium leprae?

Answer 29

acid-fast rod

Question 30

How is mycobacterium leprae transmitted?

Answer 30

when a person is exposed to respiratory secretions or skin lesions of an infected individual

Question 31

What does the clinical presentation of leprosy depend on?

Answer 31

• bacteria grow better in cooler body temperatures close to the surface
• severity depends on host’s cell mediated immune response to bacilli

Question 32

Where on the body does mycobacterium leprae damage?

Answer 32

skin, superficial nerves, eyes, nose, testes

Question 33

What are the 2 general types of leprosy?

Answer 33

1. Lepromatous leprosy (LL)

2. Tuberculoid leprosy (TL)

Question 34

Why is lepromatous leprosy the severest form of leprosy?

Answer 34

because patients canNOT mount a cell-mediated immune response

Question 35

What organs are involved in lepromatous leprosy?

Answer 35

skin, nerves, eyes, and testes

Question 36

What is the clinical presentation of a patient with lepromatous leprosy?

Answer 36

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)

Question 37

What occurs in tuberculoid leprosy (TL)?

Answer 37

Patient’s with TL can mount a cell-mediated defense against the bacteria thus have milder symptoms

Question 38

What is the clinical presentation of patient with tuberculoid leprosy?

Answer 38

localized superficial, unilateral skin and nerve involvement
well-defined, hypopigmented, elevated blotches

Question 39

What are the most frequently enlarged nerves in tuberculoid leprosy?

Answer 39

*nerves closest to skin

greater auricular, ulnar, posterior tibial, peroneal

Question 40

What is the lepromin skin test?

Answer 40

measures the ability of the host to mount a delayed hypersensitivity reaction against antigens of Mycobacterium leprae

Question 41

What is the difference between LL and TL patients when given the lepromin skin test?

Answer 41

TL patients- cell-mediated response, + test

LL patients- do not have cell-mediated response, - test

Question 42

What are nontuberculous mycobacteria (NTM)?

Answer 42

organisms that are ubiquitous in the soil and water

Question 43

When is nontuberculous mycobacteria most likely seen?

Answer 43

in AIDS patients with disseminated Mycobacterium avium-complex (MAC) disease

Question 44

What is the clinical presentation of a patient with mycobacterium avium-complex disease?

Answer 44

unexplained fevers, weight loss, diarrhea, malaise, elevation of alkaline phosphatase

Question 45

How is diagnosis of mycobacterium avium-complex confirmed?

Answer 45

growth in mycobacterial blood cultures