UAMS MICRO CASE STUDY MODULE 4
EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS 100%
CORRECT!!!
Mycobacteriology: Transmission & Screening Assays
How is Mycobacterium tuberculosis (MTB) usually transmitted between hosts?
✔✔ Inhalation of airborne aerosols (droplet nuclei created by coughing, sneezing,
or speaking).
What are the primary physical characteristics and clinical interpretations of a
positive Tuberculin Skin Test (TST)?
✔✔ Physical Finding: A red, indurated (hardened) area at the injection site.
✔✔ Clinical Significance:
Indicates the individual has been exposed to MTB.
Indicates the individual could have active TB disease.
Indicates the individual may have latent tuberculosis infection (LTBI).
(Note: TST cannot distinguish between active disease and latent infection).
,What are the primary characteristics and operational advantages of Interferon-
Gamma Release Assays (IGRAs)?
✔✔ Less subjective to reader bias and measurement errors compared to skin tests.
✔✔ Requires a blood sample (in vitro laboratory test).
✔✔ Not affected by prior BCG (Bacille Calmette-Guérin) vaccination (eliminates
false positives caused by BCG).
appearance of mycobacteria in gram stained smears
stain very poorly-if at all
recommended specimen collection procedure for urine samples for mycobacterial
cultures
3-5 morning samples over a week
No decontamination-centrifuge and inoculate media
CSF
Decontaminate specimen and inoculate 2 sets of media (30C and 35C)
Skin/wound
, no decontamination needed
pleural fluid
decontaminate specimen before inoculating media
sputum and urine
How should gastric aspirated be handled if they cannot be processed within 4 hours
neutralize specimen with sodium bicarbonate
which mycobacteria are rapid growers
M. abscesses and M. fortuitum-chelonae
how fast does a rapid grower grow
less than 7 days
if the contamination rate is too HIGH
the decontamination process is not strong enough
function of N-acetyl-L-cysteine
EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS 100%
CORRECT!!!
Mycobacteriology: Transmission & Screening Assays
How is Mycobacterium tuberculosis (MTB) usually transmitted between hosts?
✔✔ Inhalation of airborne aerosols (droplet nuclei created by coughing, sneezing,
or speaking).
What are the primary physical characteristics and clinical interpretations of a
positive Tuberculin Skin Test (TST)?
✔✔ Physical Finding: A red, indurated (hardened) area at the injection site.
✔✔ Clinical Significance:
Indicates the individual has been exposed to MTB.
Indicates the individual could have active TB disease.
Indicates the individual may have latent tuberculosis infection (LTBI).
(Note: TST cannot distinguish between active disease and latent infection).
,What are the primary characteristics and operational advantages of Interferon-
Gamma Release Assays (IGRAs)?
✔✔ Less subjective to reader bias and measurement errors compared to skin tests.
✔✔ Requires a blood sample (in vitro laboratory test).
✔✔ Not affected by prior BCG (Bacille Calmette-Guérin) vaccination (eliminates
false positives caused by BCG).
appearance of mycobacteria in gram stained smears
stain very poorly-if at all
recommended specimen collection procedure for urine samples for mycobacterial
cultures
3-5 morning samples over a week
No decontamination-centrifuge and inoculate media
CSF
Decontaminate specimen and inoculate 2 sets of media (30C and 35C)
Skin/wound
, no decontamination needed
pleural fluid
decontaminate specimen before inoculating media
sputum and urine
How should gastric aspirated be handled if they cannot be processed within 4 hours
neutralize specimen with sodium bicarbonate
which mycobacteria are rapid growers
M. abscesses and M. fortuitum-chelonae
how fast does a rapid grower grow
less than 7 days
if the contamination rate is too HIGH
the decontamination process is not strong enough
function of N-acetyl-L-cysteine
