Biochemical Tests for Pathogen Diagnosis: A Student Guide
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50 cards
Question: What is the purpose of pathogen (bacterial) diagnosis?
Answer: To identify the causative agent so appropriate treatment, infection control, and public health measures can be applied.
Question: Why are biochemical tests used in bacterial identification?
Answer: To differentiate and identify bacteria at the genus and species level, complement staining/morphology, determine metabolic capabilities, and guide dia
Question: What principle underlies bacterial biochemical tests?
Answer: Microbes have unique metabolic pathways; when grown on media with specific substrates they secrete exoenzymes or metabolize compounds producing visibl
Question: How do exoenzymes contribute to biochemical test results?
Answer: Exoenzymes secreted by bacteria break down substrates in the medium, producing observable changes (color, gas, precipitate, clearing) that indicate en
Question: Why are both positive and negative biochemical test results useful?
Answer: Because presence (+) or absence (−) of specific metabolic reactions reflects genetic differences and helps identify the pathogen.
Question: What does a positive reaction in a biochemical test generally indicate in genetic terms?
Answer: A positive reaction indicates the presence of the gene(s) encoding the enzyme or pathway responsible for that reaction.
Question: What is the role of carbohydrate (‑ose) testing in biochemical identification?
Answer: To detect bacterial ability to metabolize sugars (monomers, disaccharides, polysaccharides) such as hydrolysis of polysaccharides like starch.
Question: What enzyme breaks down starch and why is it clinically relevant?
Answer: Amylase breaks down starch; it is an exoenzyme and virulence factor that assists tissue invasion and survival, and it helps differentiate bacterial sp
Question: Which bacteria typically give a positive starch hydrolysis (amylase) test?
Answer: Positive examples: Bacillus subtilis, Bacillus cereus, Pseudomonas aeruginosa.
Question: Which bacteria are typically negative or variable for starch hydrolysis?
Answer: Negative or variable: Staphylococcus aureus (variable) and Escherichia coli.