Quiz 2 - Hanson - Clinical Mycobacteriology

Question 1

Describe mycobacteria.

Answer 1

Bacilli
Obligate aerobes
Mycolic acid in cell wall

*Acid fast bacilli - binds carbon fuchsin dye so that it is not removed by acid alcohol

Question 2

What mycobacterium causes TB?

Answer 2

Mycobacterium tuberculosis

Question 3

How is TB transmitted?

Answer 3

Respiratory route

*Particles can remain suspended in air for several hours and spread up to 6 m away at 50 m/s

Question 4

What is the life cycle of a TB infection?

Answer 4

Transmission
Infection (symptomatic or asymptomatic)
Latent phase (asymptomatic)
Reactivation (Immunocompromised state)
Infection - Cavitation (symptomatic)
Transmission

Question 5

Name 5 groups of people that have an increased likelihood of exposure to TB.

Answer 5

Close contacts

Health care workers

Congregate settings (Prisons, shelters, nursing homes)

IV drug abusers

Immigrants

Question 6

What is a delayed hypersensitivity test? (The skin test for TB)

Answer 6

Antigen introduced subcutaneously

Effector cell recognizes antigen and releases cytokines which act on vascular endothelium

Recruitment of T cells, fluid and protein to the injection site result in induration

Question 7

Explain the 2 step TST testing.

Answer 7

Injection
Negative - Retest 3 weeks later
Positive - Probable TB infection

Retest
Negative - Unprobable TB infection
Positive - “Boosted rxn” (from a TB infection that occurred a long time ago. Follow up and evaluate for LTBI treatment

Question 8

What are IGRAs?

Answer 8

Blood put into tubes and exposed to antigens. Interferon gamma is measured

Question 9

T/F - TB test do not tell you if a patient has active TB.

Answer 9

TRUE - Just that they’ve seen the TB infection before in life or not

Question 10

Explain Cavitary TB.

Answer 10

Lung lesion in apex of lung. Most infectious form of TB, b/c cavity is filled with TB organisms and they spill out each time the patient sneezes

Question 11

Explain Milliary TB.

Answer 11

White-speckled lungs. Could be deactivated or primary TB. Comes from TB infection from the blood, not the lung. A disseminated form usually seen in young kids.

Question 12

Why differentiate latent TB vs infected?

Answer 12

Treatment and infection control measures are different

Question 13

What are three samples that can be used for a TB test?

Answer 13

Respiratory sample

Sterile tissue/body fluid

Urine if signs of UTI

Question 14

What does the NAAT do?

Answer 14

Direct from sputum, uses polymerase chain reaction, can detect TB very quickly.

Question 15

Tell me what a photochromogen is.

Answer 15

Runyon I (NTM, non-tuberculosis mycobacteria)

Slow growth

Yellow-orange pigment when exposed to light

Question 16

Tell me what scotochromogens are.

Answer 16

Runyon II

Slow growth

Yellow-orange pigment in light or dark

Question 17

Tell me what nonchromogenic is.

Answer 17

Runyon III

Slow growth

No pigment

Question 18

Tell me what a rapid grower is.

Answer 18

Runyon IV

Rapid growth

May or may not be pigment