Laboratory Science Microbiology Techniques 2

Question 1

What does MIC stand for in antimicrobial susceptibility testing?

Accepted Answer

Minimum Inhibitory Concentration

Answer

MIC (Minimum Inhibitory Concentration) is the lowest concentration of an antibiotic that inhibits visible bacterial growth, guiding antibiotic selection in clinical therapy.

Question 2

Which staining technique is used to identify Mycobacterium tuberculosis?

Accepted Answer

Ziehl-Neelsen (acid-fast) stain

Answer

The Ziehl-Neelsen stain uses carbol fuchsin that binds mycobacterial cell wall mycolic acids; acid-fast bacilli resist decolorization with acid-alcohol, appearing red.

Question 3

Blood cultures are typically incubated for how many days before being reported as negative?

Accepted Answer

5 days

Answer

Most clinical blood cultures are incubated for 5 days in automated systems (e.g., BACTEC), which is sufficient to detect the vast majority of clinically significant bacteremia.

Question 4

What is a presumptive identification when a beta-hemolytic Streptococcus is sensitive to bacitracin?

Accepted Answer

Streptococcus pyogenes (Group A)

Answer

Group A Streptococcus (S. pyogenes) is sensitive to bacitracin (A disk), while other beta-hemolytic streptococci are resistant, providing a presumptive identification.

Question 5

Which organism produces a characteristic 'school of fish' arrangement on gram stain?

Accepted Answer

Corynebacterium diphtheriae

Answer

Corynebacterium diphtheriae cells arrange in palisades (rows) or V/L shapes resembling a 'school of fish' or 'Chinese letters' on Gram stain.

Laboratory Science Practice Test

Laboratory Science Practice Test

Laboratory Science Microbiology Techniques 2