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Microbiology Exam 3 > Lecture 25 > Flashcards

Lecture 25 Flashcards

actinobacteria 1: Mycobacteria

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1
Q

Describe the progression of TB in the human body

A
  • infection enters the lung
  • body builds a barrier (tubercle) around the bacteria to contain them [latent stage]
  • the bacteria break out of the tubercles [primary/pulmonary TB]
  • the bacteria spread out from lungs through the blood to areas including the bones and lymphatic system [extrapulmonary TB]
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1
Q

What is rifater?

A

a pill to treat TB

contains:

isonizid

rifampin

pyrazinamide

used during empiric initial treatment, and once it is discovered that the TB strain is susceptible to antibiotics

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2
Q

How many latent cases of TB in the world? In the USA?

A
  • 1/3 of the world has latent TB
  • 15 million people in the USA have latent TB
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2
Q

Describe how to interpret the results of a mantaux test

A

5-10-15 scale (positive means TB exposure)

<5mm is negative for everyone

5-9mm is a positive for:

  • immunocompromised patients (AIDS)
  • people who live with someone with TB
  • people with healed TB

10-14mm is a positive for:

  • people who are foreign born
  • IV drug users
  • residents in a long term care facility
  • severe diabetics

15mm is a positive for everyone

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3
Q

What form of TB do x-rays test for?

A

if the TB has become cavitary (very large tubercles)

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3
Q

How can you get a false positive with a skin test for TB?

A

if the patient has been vaccinated against TB before

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4
Q

Your strain of TB is found to be susceptible, and you have 0 risk factors.

What is your course of treatment? How long does it take?

A
  • 2 months of rifater (which includes the original month from empiric initial treatment)
  • this is followed by rifimate (INH and rifampin) for 4 months
  • treatment takes 6 months
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6
Q

What is the etiology of TB? (include all 4 species)

A

Mycobacterium is the genus

  • M. tuberculosis
  • M. bovis
  • M. kansasii (MOTTS)
  • M. aviam (MOTTS)
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6
Q

At what age does a negative result on the mantaux test become a bad thing and why?

A

if you are over 40 and especially over 60

because you should have antibodies against TB, but since you don’t you are more susceptible to infection

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8
Q

Your strain of TB is found to be susceptible, and you have only 1 risk factor. What is your course of treatment? How long does it take?

A
  • 2 months of rifater (which includes the original month from empiric initial treatment)
  • this is followed by rifimate (INH and rifampin) for 4 months
  • treatment takes 6 months
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9
Q

What is XDR TB resistant to?

A
  • INH
  • rifampin
  • fluroquinolone (such as ciprofloxacin)
  • and any injectable aminoglycocide (such as amikacin, capreomycin, kanamycin)
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10
Q

Which tests diagnose active TB?

A
  • sputum smear
  • culture
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10
Q

What is DOT?

A
  • directly observe therapy you watch the patient take their medications to ensure compliance
  • has a higher cure rate than just relying on the patient
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12
Q

Describe the mycobacterium (growth medium, colony morphology, gram staining)

A
  • gram non reactive (b/c of waxy coating)
  • Stain with acid fast
  • grow on lowenstein jensen (colonies will look dry, crumbly)
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13
Q

What is the defining characteristic of miliary TB?

A

skin lesions that look like millet seeds

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14
Q

How many active cases of TB in the world each year? In the USA?

A

8.8 million in the world

13,000 in the USA

14
Q

What is the incubation period of TB?

A

6 months

15
Q

How can you diagnose TB? (4)

A
  • sputum (spit) smear
  • taking a culture
  • x-ray
  • skin tests
16
Q

Describe the mantaux test including what it intails and what a result looks like

A
  • inject purified protein derivitave (PPD) just under the skin
  • after 3 days a bump/erythma at the injection site occurs (in all cases)
  • the diameter of the erythma determines if the test is positive or negative
  • determines if someone has been exposed to TB
17
Q

What are some methods of prevention of TB?

A
  • quarantine of the infected
  • education for the infected
  • INH as a chemopropylaxis
  • BCG vaccine (more effective in children)
19
Q

Which skin test for TB is preferred?

A

mantaux test

20
Q

How many TB deaths each year in the world? In the USA?

A

1.5 million deaths worldwide

2,000 deaths in the USA

21
Q

What happens if after 4 months of treatment with rifater and rifampin you still test positive?

A

your treatment is not working, possibly due to resistance

it needs to be switched to something else

22
Q

What is the treatment for MDR and XDR TB?

A

4-7 drugs that the strain is susceptable to

treatment is for 18-24 months

culture is taken once a month to check for progress

23
Q

Your strain of TB is found to be susceptible, and you have 2 risk factors. What is your course of treatment? How long does it take?

A
  • 2 months of rifater (including original month from empiric treatment)
  • follow this with 7 months of rifimate
  • treatment takes 9 months total
25
Q

What is the mode of transmission of TB?

A

microaerosols (coughing makes droplets)

26
Q

What is MDR TB resistant to?

A

INH and rifampin

27
Q

What happens during empiric initial treatment?

A

done immediately after diagnosis for a month

give rifater and ethambutol drugs

28
Q

What is INH used to treat?

A

latent TB in high risk patients as a preventative (chemoprophylactic)

29
Q

What is the new test for TB?

A
  • interferon gamma release asst. (IGRA)
  • you test for 2 antigens found almost exclusively in the organism
  • will NOT react with m. bovis or MOTTS
30
Q

How can you get a false negative with a skin test for TB?

A

tuberculin anergy (antibodies are too busy fighting TB infection to be present at the test)

31
Q

What are skin tests for TB looking for?

A

if the patient has antibodies against TB

32
Q

At what age is it rare or very rare to have antibodies against TB?

A

anywhere from birth to 30 years old (7 years is the cut off for very rare to rare)

33
Q

Where is osseous TB found?

A

in the bones

35
Q

Which tests diagnose latent TB?

A

none of them!

36
Q

What TB drug do bacteria most commonly have a resistance to? What drug should be used to replace it?

A

INH resistance is common

use all of the following to replace it:

  • rifampin
  • pyrazinamide
  • ethambutol OR streptomycin

Microbiology Exam 3 (11 decks)

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