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A patient presented with fever and cough. A sputum sample stained by Gram's method revealed Gram-positive diplococci with a capsule. What is the likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Neisseria meningitidis
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive diplococci with a capsule is characteristic of S. pneumoniae. This bacterium is a common cause of pneumonia, especially in patients with fever and cough. It is also known for causing infections such as otitis media and sinusitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form diplococci or have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus commonly associated with meningitis, not pneumonia. Klebsiella pneumoniae (D) is a Gram-negative rod, not a diplococcus, and is more commonly associated with pneumonia in immunocompromised patients.
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A patient ill with amebiasis was prescribed a certain drug. The use of alcohol together with this drug is contraindicated because the drug inhibits metabolism of ethyl alcohol. What drug is it?
- A. Metronidazole
- B. Reserpine
- C. Clonidine
- D. Diazepam
Correct Answer: A
Rationale: Rationale:
1. Metronidazole is known to inhibit aldehyde dehydrogenase, an enzyme involved in alcohol metabolism.
2. Inhibition of this enzyme leads to accumulation of acetaldehyde, causing unpleasant symptoms when alcohol is consumed.
3. This reaction is known as the disulfiram-like reaction.
4. Reserpine, Clonidine, and Diazepam do not have this specific mechanism of action.
Summary:
- Option A (Metronidazole) is correct due to its inhibition of alcohol metabolism.
- Options B, C, and D are incorrect as they do not exhibit this interaction with alcohol metabolism.
A scolex is a structure found in:
- A. Enterobius vermicularis
- B. Necator americanus
- C. Ascaris lumbricoides
- D. Ancylostoma duodenale
Correct Answer: D
Rationale: The correct answer is D: Ancylostoma duodenale. A scolex is a structure found in tapeworms, not in the other options which are roundworms. Ancylostoma duodenale is a species of hookworm, a type of intestinal parasite that has a distinct scolex with hook-like mouthparts for attachment to the host's intestinal wall. Enterobius vermicularis is a pinworm, Necator americanus is a hookworm species without a scolex, and Ascaris lumbricoides is a roundworm with a cylindrical body lacking a scolex. Therefore, the presence of a scolex specifically points to Ancylostoma duodenale.
Which of the following does NOT describe Cephalosporins
- A. relatively broad spectrum
- B. bactericidal
- C. beta-lactam
- D. interferes with protein synthesis
Correct Answer: D
Rationale: The correct answer is D: interferes with protein synthesis. Cephalosporins are beta-lactam antibiotics that work by inhibiting bacterial cell wall synthesis, not protein synthesis. They are bactericidal and have a relatively broad spectrum of activity against various bacteria. Choice A, B, and C all describe characteristics of cephalosporins, making them incorrect options.
All bacteria are __________ cells.
- A. eukaryotic
- B. prokaryotic
- C. diploid
- D. haploid
Correct Answer: B
Rationale: The correct answer is B: prokaryotic. Bacteria are prokaryotic cells because they lack a true nucleus and membrane-bound organelles. They have a simple cell structure with genetic material floating freely in the cytoplasm. Choice A (eukaryotic) is incorrect because eukaryotic cells have a nucleus and membrane-bound organelles. Choice C (diploid) is incorrect as bacteria do not have a defined ploidy level like diploid organisms do. Choice D (haploid) is also incorrect as bacteria do not have a true haploid or diploid state due to their lack of a defined nucleus.
Which are the most suitable materials for isolation of polio viruses
- A. feces, duodenal and bile content
- B. blood, sputum and urine
- C. only feces
- D. feces, nasopharyngeal swabs and cerebrospinal fluid
Correct Answer: D
Rationale: The correct answer is D because polio viruses are primarily found in the gastrointestinal tract and respiratory secretions. Feces, nasopharyngeal swabs, and cerebrospinal fluid are the most suitable materials for isolating polio viruses due to their presence in these body fluids. Feces contain the virus shed from the intestines, nasopharyngeal swabs collect respiratory secretions where the virus may be present, and cerebrospinal fluid is important for detecting the virus in cases of neurological complications. Choices A and B include irrelevant body fluids that are not typically associated with polio virus transmission. Option C is too limited as the virus can also be present in respiratory secretions and cerebrospinal fluid, not just feces.