CLS CLS Clinical Microbiology and Immunology

Question 1

Which organism is identified by oxidase-positive results, blue-green pigment (pyocyanin), and a grape-like odor?

Accepted Answer

Pseudomonas aeruginosa

Answer

Escherichia coli

Answer

Klebsiella pneumoniae

Answer

Proteus mirabilis

Question 2

The catalase test is used to differentiate which two clinically important genera?

Accepted Answer

Staphylococcus (positive) from Streptococcus (negative)

Answer

Gram-positive from Gram-negative bacteria

Answer

Aerobic from anaerobic organisms

Answer

Lactose fermenters from non-fermenters

Question 3

Which agar medium is both selective (for gram-negatives) and differential (for lactose fermentation)?

Accepted Answer

MacConkey agar

Answer

Blood agar

Answer

Chocolate agar

Answer

Mannitol salt agar

Question 4

The VDRL (Venereal Disease Research Laboratory) test is used to screen for which sexually transmitted infection?

Accepted Answer

Syphilis

Answer

HIV

Answer

Hepatitis B

Answer

Gonorrhea

Question 5

Which gram-negative rod produces urease, causes struvite kidney stones, and displays 'swarming' motility on agar?

Accepted Answer

Proteus mirabilis

Answer

Escherichia coli

Answer

Klebsiella pneumoniae

Answer

Enterococcus faecalis

Question 6

What is the gold standard method for definitive diagnosis of Mycobacterium tuberculosis infection?

Accepted Answer

Mycobacterial culture

Answer

Tuberculin skin test (TST)

Answer

Chest X-ray

Answer

QuantiFERON-TB Gold test