Nokea
The mold responsible for the production of penicillin belongs to the subgroup of:
- A. Basidiomycota
- B. Ascomycota
- C. Zygomycota
- D. Deuteromycota
Correct Answer: B
Rationale: The correct answer is B: Ascomycota. Penicillin is produced by the mold Penicillium, which belongs to the phylum Ascomycota. Ascomycota is known for its sac-like structures called asci that contain ascospores. Penicillium produces penicillin as a defense mechanism against bacteria. Basidiomycota (A) are known for producing mushrooms, Zygomycota (C) includes bread molds like Rhizopus, and Deuteromycota (D) is a classification for fungi with no known sexual reproductive stage.
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A defined microorganism can be isolated in pure culture:
- A. From liquid and solid media
- B. From liquid nutrient media
- C. Only from single colonies on solid media
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C because isolating a defined microorganism in pure culture involves obtaining a single, distinct colony on solid media. This ensures that only one type of microorganism is present in the culture, preventing contamination. Liquid media can harbor multiple organisms, making it challenging to isolate a specific microorganism. Therefore, choice A is incorrect. Choice B is also incorrect as liquid nutrient media does not provide the necessary isolation required for pure culture. Choice D is incorrect because isolating from single colonies on solid media allows for the pure culture of the defined microorganism.
Disinfection with chemicals acting on cell surface:
- A. Soaps
- B. Phenols
- C. Amines
- D. Polymyxin
Correct Answer: B
Rationale: The correct answer is B: Phenols. Phenols act on the cell surface by disrupting cell membranes and denaturing proteins, leading to cell death. Soaps (A) work by lifting dirt and microbes off surfaces, not directly acting on cell surfaces. Amines (C) are typically used as disinfectants targeting specific enzymes in microbes, not cell surfaces. Polymyxin (D) is an antibiotic that works by disrupting cell membranes internally, not on the cell surface.
During sanitary and bacteriological testing of water with the membrane filter technique there were revealed two red colonies on a membrane filter (Endo agar) through which 500 ml of water was filtred. Calculate the coli index and coli titer of the analyzed water:
- A. 4 and 250
- B. 2 and 500
- C. 250 and 4
- D. 500 and 2
Correct Answer: C
Rationale: The correct answer is C (coli index of 250 and coli titer of 4). The coli index is calculated by multiplying the number of colonies by the reciprocal of the volume filtered, which gives 2 colonies x (1/0.5 L) = 4. The coli titer is obtained by dividing the volume filtered by the number of colonies, which gives 0.5 L / 2 colonies = 0.25 L or 250 ml. This indicates the concentration of coliform bacteria in the water sample.
Choice A (4 and 250) is incorrect because it has the correct coli index but the values are reversed for coli index and coli titer. Choice B (2 and 500) is incorrect as it provides the correct coli titer value but the values are reversed for coli index and coli titer. Choice D (500 and 2) is incorrect because it reverses the values for both coli index and coli titer.
An 18-year-old patient has developed candidiasis after the case of pneumonia treated with β-lactam antibiotic. What antimycotic agent should be prescribed?
- A. Fluconazole
- B. Streptomycin
- C. Phthalylsulfathiazole
- D. Ampicillin
Correct Answer: A
Rationale: The correct answer is A: Fluconazole.
1. Fluconazole is an antifungal agent effective against Candida species commonly causing candidiasis.
2. Streptomycin (B) is an antibiotic used for bacterial infections, not fungal.
3. Phthalylsulfathiazole (C) is an antibacterial agent, not antifungal.
4. Ampicillin (D) is a β-lactam antibiotic, which can actually contribute to fungal infections like candidiasis.
A patient with a productive cough and fever had a sputum smear revealing Gram-positive cocci in clusters. What is the most likely causative agent?
- A. Staphylococcus aureus
- B. Streptococcus pneumoniae
- C. Neisseria meningitidis
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. Staphylococcus aureus is a Gram-positive cocci bacterium that forms clusters and commonly causes pneumonia with a productive cough and fever. It is frequently found in sputum smears in such cases. Streptococcus pneumoniae (B) is another common cause of pneumonia but typically appears in pairs or chains, not clusters. Neisseria meningitidis (C) is a Gram-negative diplococcus that causes meningitis, not pneumonia. Klebsiella pneumoniae (D) is a Gram-negative bacterium that can cause pneumonia but appears as Gram-negative rods, not Gram-positive cocci in clusters.