Microbiology Techniques Flashcards
6 cards from real Laboratory Science practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Microbiology Techniques flashcards as text
What does MIC stand for in antimicrobial susceptibility testing?
Answer: Minimum Inhibitory Concentration
MIC (Minimum Inhibitory Concentration) is the lowest concentration of an antibiotic that inhibits visible bacterial growth, guiding antibiotic selection in clinical therapy.
Which staining technique is used to identify Mycobacterium tuberculosis?
Answer: Ziehl-Neelsen (acid-fast) stain
The Ziehl-Neelsen stain uses carbol fuchsin that binds mycobacterial cell wall mycolic acids; acid-fast bacilli resist decolorization with acid-alcohol, appearing red.
Blood cultures are typically incubated for how many days before being reported as negative?
Answer: 5 days
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.
What is a presumptive identification when a beta-hemolytic Streptococcus is sensitive to bacitracin?
Answer: Streptococcus pyogenes (Group A)
Group A Streptococcus (S. pyogenes) is sensitive to bacitracin (A disk), while other beta-hemolytic streptococci are resistant, providing a presumptive identification.
Which organism produces a characteristic 'school of fish' arrangement on gram stain?
Answer: Corynebacterium diphtheriae
Corynebacterium diphtheriae cells arrange in palisades (rows) or V/L shapes resembling a 'school of fish' or 'Chinese letters' on Gram stain.
What is the purpose of the indole test in identifying Enterobacteriaceae?
Answer: Detect tryptophan degradation to indole by tryptophanase
The indole test detects tryptophanase activity: positive organisms (like E. coli) degrade tryptophan to indole, producing a red ring with Kovac's reagent.