The First-line tuberculosis drugs include:
- A. Isoniazid and rifampicin
- B. Penicillin and erythromycin
- C. Trimethoprim and third generation cephalosporins
- D. All the listed above can be used depending on their resistance profile
Correct Answer: A
Rationale: The correct answer is A: Isoniazid and rifampicin. These drugs are considered first-line treatment for tuberculosis due to their high efficacy and low toxicity. Isoniazid targets the cell wall of the tuberculosis bacteria, while rifampicin inhibits RNA synthesis. They are recommended by WHO as the first choice for treating tuberculosis.
Choice B (Penicillin and erythromycin) is incorrect because these antibiotics are not effective against tuberculosis bacteria.
Choice C (Trimethoprim and third generation cephalosporins) is incorrect because they are not considered first-line drugs for tuberculosis treatment.
Choice D (All the listed above can be used depending on their resistance profile) is incorrect because only isoniazid and rifampicin are universally recognized as first-line drugs for tuberculosis regardless of resistance profile.
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One of the basic principles of chemotherapy is:
- A. Selective toxicity
- B. Accumulation in the macroorganism
- C. Causing allergies to the macroorganism
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Selective toxicity. Chemotherapy aims to target cancer cells while minimizing harm to healthy cells, known as selective toxicity. This principle is crucial to effectively treat cancer without causing excessive damage to the patient's body. Accumulation in the macroorganism (B) and causing allergies (C) are not fundamental principles of chemotherapy and can lead to harmful side effects. Therefore, the correct answer is A as it aligns with the core objective of chemotherapy.
Microscopy of a wound abscess revealed Gram-negative rods producing blue-green pigment with a distinctive odor of jasmine. What is the likely causative agent?
- A. Pseudomonas aeruginosa
- B. Proteus vulgaris
- C. Escherichia coli
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known for producing a blue-green pigment called pyocyanin, which gives the characteristic color seen in the wound abscess. The distinctive odor of jasmine is also a key feature of Pseudomonas aeruginosa. Proteus vulgaris (B) and Klebsiella pneumoniae (D) do not produce blue-green pigment or have a jasmine-like odor. Escherichia coli (C) typically does not produce blue-green pigment or have a jasmine-like odor.
Chlorine belongs to which of the following chemical groups?
- A. Halogens
- B. Heavy metals
- C. Phenols
- D. Alcohols
Correct Answer: A
Rationale: The correct answer is A: Halogens. Chlorine belongs to the halogens group because it is a nonmetal element in group 17 of the periodic table. Halogens are highly reactive elements that have 7 electrons in their outer shell, making them eager to gain an electron to achieve stability. Chlorine specifically is a diatomic molecule with the chemical symbol Cl and atomic number 17.
Option B: Heavy metals are elements with high atomic weights and densities, such as lead and mercury, which are not related to chlorine.
Option C: Phenols are a class of organic compounds containing a hydroxyl group bonded to an aromatic ring, not related to chlorine.
Option D: Alcohols are organic compounds characterized by the presence of a hydroxyl group (-OH), also not related to chlorine.
A 34 year old male patient consulted a doctor about face carbuncle. Objectively: a loose, painless edema of hypodermic tissue; black crust in the center of carbuncle, vesicular rash around it. Microbiological examination revealed static streptobacilli capable of capsule building. What microorganisms are the causative agents of this disease?
- A. Bacillus antracis
- B. Staptylococcus aureus
- C. Bacillus subtilis
- D. Bacillus anthracoides
Correct Answer: B
Rationale: The correct answer is B: Staphylococcus aureus. This bacterium is a common causative agent of skin infections like carbuncles. Staphylococcus aureus is known for its ability to produce pus-filled abscesses, which aligns with the symptoms described in the question. The presence of a vesicular rash around the carbuncle further supports this diagnosis, as Staphylococcus aureus can cause skin lesions. The other choices are not correct because:
A: Bacillus anthracis causes anthrax, which presents with different symptoms such as fever, malaise, and respiratory symptoms.
C: Bacillus subtilis is a harmless soil bacterium commonly used in research and not known to cause skin infections.
D: Bacillus anthracoides is not a known pathogen and is not associated with human infections.
What would be the conclusion?
- A. The water is safe for consumption
- B. The water quality is doubtful
- C. The water quality is extremely doubtful
- D. The water is polluted
Correct Answer: B
Rationale: Step-by-step rationale for choice B being correct:
1. The conclusion should be based on evidence or observations.
2. "Doubtful" suggests uncertainty, indicating lack of definitive safety.
3. Choice A is too absolute without considering potential risks.
4. Choice C uses extreme language without proper evidence.
5. Choice D is overly definitive without considering varying levels of contamination. Therefore, choice B is the most reasonable conclusion.
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