Nokea
The bacterial species that is resistant to novobiocin is:
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Staphylococcus saprophyticus
- D. none of the listed
Correct Answer: C
Rationale: The correct answer is C: Staphylococcus saprophyticus. The rationale is that Staphylococcus saprophyticus is the only one among the listed species that is known to be resistant to novobiocin. This resistance is due to the specific mechanism of action of novobiocin, which targets DNA gyrase, and Staphylococcus saprophyticus possesses an altered DNA gyrase enzyme that renders it resistant to the antibiotic. Staphylococcus aureus and Staphylococcus epidermidis are susceptible to novobiocin, making choices A and B incorrect. Choice D, "none of the listed," is also incorrect as Staphylococcus saprophyticus is indeed resistant to novobiocin.
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A 35-year-old man was diagnosed with cutaneous leishmaniasis. What is the vector of the causative agent?
- A. Sandfly
- B. Tick
- C. Mosquito
- D. Tsetse fly
Correct Answer: A
Rationale: The correct answer is A: Sandfly. Cutaneous leishmaniasis is transmitted by the bite of infected sandflies. These tiny insects are known vectors for Leishmania parasites. Sandflies are active during dusk and night, feeding on blood from mammals, including humans. Tick (B), mosquito (C), and tsetse fly (D) are not vectors for Leishmania parasites. Ticks transmit diseases like Lyme disease, mosquitoes transmit diseases like malaria, and tsetse flies transmit African trypanosomiasis. Therefore, the correct vector for cutaneous leishmaniasis is the sandfly due to its specific role in transmitting the Leishmania parasite.
Which of the following bacteria can form spores that are resistant to extreme conditions?
- A. Staphylococcus aureus
- B. Bacillus subtilis
- C. Pseudomonas aeruginosa
- D. Neisseria gonorrhoeae
Correct Answer: B
Rationale: The correct answer is B: Bacillus subtilis. Bacillus subtilis is a Gram-positive bacterium known for forming endospores, which are resistant structures that allow the bacteria to survive harsh conditions like heat, radiation, and desiccation. This ability to form spores helps Bacillus subtilis to endure unfavorable environments. Staphylococcus aureus (A), Pseudomonas aeruginosa (C), and Neisseria gonorrhoeae (D) do not form spores and lack the same level of resistance to extreme conditions as Bacillus subtilis.
Ziehl-Neelsen staining is for detection of:
- A. Acid-resistant bacteria
- B. Spores
- C. Metachromatic bodies
- D. None of the above
Correct Answer: A
Rationale: Step 1: Ziehl-Neelsen staining is a type of acid-fast staining used to detect acid-resistant bacteria like Mycobacterium species.
Step 2: Acid-resistant bacteria have a high lipid content in their cell walls, making them resist decolorization with acid-alcohol.
Step 3: Mycobacterium species, such as M. tuberculosis and M. leprae, are examples of acid-resistant bacteria.
Step 4: Spores are not typically stained using Ziehl-Neelsen staining, making choice B incorrect.
Step 5: Metachromatic bodies are stained using specific techniques like Albert's stain, not Ziehl-Neelsen staining, making choice C incorrect.
Summary: Ziehl-Neelsen staining is specifically used for acid-resistant bacteria detection, making choice A the correct answer. Choices B and C are incorrect as they do not align with the purpose of Ziehl-Neelsen staining. Choice D is incorrect as Ziehl
A 30 y.o. patient is diagnosed with amebic dysentery. This diagnosis was bacteriologically confirmed. Name the preparation for its treatment:
- A. Metronidazole
- B. Mebendazole
- C. Itrakonazole
- D. Furacillin
Correct Answer: A
Rationale: The correct answer is A: Metronidazole. Amebic dysentery is caused by the parasite Entamoeba histolytica, not bacteria. Metronidazole is the drug of choice for treating this parasitic infection. It works by disrupting the DNA structure of the parasite, leading to its death. Mebendazole (B) is used to treat certain worm infections, not amebic dysentery. Itrakonazole (C) is an antifungal medication and not effective against parasites. Furacillin (D) is an antibacterial agent and not suitable for treating parasitic infections like amebic dysentery.
Which of the following pathogens can be transmitted through the placenta?
- A. Listeria monocytogenes
- B. Staphylococcus aureus
- C. Corynebacterium diphtheriae
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Listeria monocytogenes. This pathogen can cross the placenta and infect the fetus, leading to serious complications. Listeria can cause miscarriage, stillbirth, or severe neonatal infections. Staphylococcus aureus and Corynebacterium diphtheriae do not typically cross the placenta. Choice D is incorrect because Listeria monocytogenes can indeed be transmitted through the placenta, unlike the other pathogens listed.