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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.
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Which bacteria is responsible for causing the disease known as tuberculosis?
- A. Mycobacterium leprae
- B. Mycobacterium tuberculosis
- C. Streptococcus pneumoniae
- D. Clostridium botulinum
Correct Answer: B
Rationale: The correct answer is B: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis as it specifically infects the lungs and can spread through the air. Mycobacterium leprae (choice A) causes leprosy, not tuberculosis. Streptococcus pneumoniae (choice C) is a common cause of pneumonia but not tuberculosis. Clostridium botulinum (choice D) causes botulism, a different disease unrelated to tuberculosis. Therefore, the unique characteristics and infection pattern of Mycobacterium tuberculosis make it the correct choice for the bacteria responsible for causing tuberculosis.
Disinfection is:
- A. method for destruction of spore forms of microorganisms
- B. method for destruction of vegetative and spore forms of microorganisms
- C. method to destroy the vegetative forms of microorganism, but their spores may survive
- D. method for determination of the effect of physical agents on the microorganism
Correct Answer: C
Rationale: Disinfection is the process of destroying the vegetative forms of microorganisms, but their spores may survive. This is why choice C is correct. The other choices are incorrect because:
A: Disinfection does not necessarily target spore forms exclusively.
B: While disinfection targets vegetative forms, it does not always eliminate spore forms.
D: Disinfection is not primarily used for determining the effect of physical agents on microorganisms.
Which of the following viruses belong to the family Herpesviridae?
- A. Epstein-Barr virus
- B. Poxvirus
- C. SARS
- D. HIV
Correct Answer: A
Rationale: Step-by-step rationale for the correct answer (A: Epstein-Barr virus):
1. Epstein-Barr virus is a member of the Herpesviridae family, known for causing infectious mononucleosis.
2. Members of Herpesviridae have double-stranded DNA genomes and enveloped virions.
3. They establish latent infections in host cells and can reactivate periodically.
4. Poxvirus (B) belongs to the Poxviridae family, not Herpesviridae.
5. SARS (C) is caused by a coronavirus, not a herpesvirus.
6. HIV (D) belongs to the Retroviridae family, not Herpesviridae.
Summary: The correct answer is A because Epstein-Barr virus is a member of the Herpesviridae family, exhibiting specific characteristics distinct from the other choices.
The bacterium that shows swarming on blood agar
- A. providencia stuartii
- B. providencia rettgeri
- C. Proteus mirabilis
- D. morganella morganii
Correct Answer: C
Rationale: The correct answer is C: Proteus mirabilis. This bacterium shows swarming on blood agar due to its ability to produce flagella and exhibit rapid and coordinated movement. Providencia stuartii and Providencia rettgeri are not known for swarming behavior on blood agar. Morganella morganii can exhibit swarming motility, but it is not as commonly associated with this characteristic compared to Proteus mirabilis, making C the most appropriate choice.
Microscopic examination of a smear from a patient with diphtheria revealed dark blue-staining granules at the ends of rod-shaped bacteria. What staining technique was likely used?
- A. Neisser's staining
- B. Ziehl-Neelsen staining
- C. Gram staining
- D. Giemsa staining
Correct Answer: A
Rationale: The correct answer is A: Neisser's staining. Neisser's staining is used to detect metachromatic granules in bacteria, which appear as dark blue-staining granules at the ends of rod-shaped bacteria in diphtheria. This technique specifically targets these granules, making it ideal for identifying Corynebacterium diphtheriae, the causative agent of diphtheria. Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, Gram staining is for classifying bacteria based on cell wall composition, and Giemsa staining is used for detecting parasites and certain blood cells, making them incorrect for identifying granules in diphtheria.