Bacterial Identification: Biochemical & Serological Tests Guide
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53 cards
Question: What is the substrate in the starch (amylase) hydrolysis test?
Answer: Starch (a complex polysaccharide).
Question: What enzyme do some bacteria secrete to hydrolyze starch, and why is it clinically relevant?
Answer: Amylase (an exoenzyme); it is a virulence factor that aids tissue invasion and survival and helps identify organisms.
Question: Which organisms are listed as positive for starch hydrolysis in the provided data?
Answer: Bacillus subtilis, Bacillus cereus, and Pseudomonas aeruginosa.
Question: Which organisms are listed as negative or variable for starch hydrolysis in the provided data?
Answer: Escherichia coli is negative; Staphylococcus aureus is variable (may be negative).
Question: How is the starch agar test performed (basic steps)?
Answer: Streak bacteria on starch agar, incubate at room temperature for 48 hours, then add a few drops of Gram's iodine and wait at least 5 minutes for the a
Question: How do you interpret a positive starch hydrolysis result after adding Gram's iodine?
Answer: A positive result shows a clear, golden zone around the bacterial growth where starch has been hydrolyzed.
Question: How do you interpret a negative starch hydrolysis result after adding Gram's iodine?
Answer: A negative result shows a dark (black/brown or purple) area around the bacteria where starch remains and binds iodine.
Question: What is the role of Gram's iodine in the starch hydrolysis test?
Answer: Gram's iodine acts as an indicator by staining intact starch dark (black/brown), allowing zones of hydrolysis to appear light/clear.
Question: Clinical uses of the starch (amylase) hydrolysis test — what identification information does it provide?
Answer: Differentiates Bacillus species from non-spore-formers, supports identification of environmental Gram-positive rods, and confirms enzyme profiles in i
Question: What does the fermentation of carbohydrates test assess in enteric bacteria?
Answer: It tests an organism's ability to ferment specific sugars, distinguishing those that produce organic acids only from those that produce acids plus gas