Nokea
Laboratory diagnosis of rabies includes all of these except:
- A. Looking for Negri bodies
- B. Intracerebrally infected mice
- C. Looking for Ernst-Babes granules
- D. Immunofluorescence method
Correct Answer: C
Rationale: The correct answer is C: Looking for Ernst-Babes granules. Laboratory diagnosis of rabies typically involves looking for Negri bodies in the brain tissue, intracerebrally infecting mice for virus isolation, and using immunofluorescence method to detect viral antigens. Ernst-Babes granules are not associated with rabies virus and are not used in the diagnosis of rabies. Therefore, choice C is incorrect.
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The most important virulence factor of Neisseria meningitidis is:
- A. Exotoxin
- B. Polysaccharide capsule
- C. Beta-lactamase
- D. Pyrogenic toxin
Correct Answer: B
Rationale: The correct answer is B: Polysaccharide capsule. The capsule of Neisseria meningitidis is crucial for its virulence as it helps the bacteria evade the host immune system by inhibiting phagocytosis. This allows the bacteria to survive and multiply in the host, leading to invasive infections. Exotoxins, beta-lactamase, and pyrogenic toxins are not the main virulence factors of Neisseria meningitidis and do not play as significant a role in its pathogenicity as the polysaccharide capsule.
For Parvovirus B19 it is true that:
- A. Its genome consists of dsDNA
- B. Is an enveloped virus
- C. Has segmented genome
- D. There are three structural proteins
Correct Answer: A
Rationale: Step-by-step rationale for choice A being correct:
1. Parvovirus B19 is a single-stranded DNA (ssDNA) virus.
2. The prefix "parvo-" indicates small size, characteristic of ssDNA viruses.
3. ssDNA viruses replicate in the host cell by converting their ssDNA genome into double-stranded DNA (dsDNA).
4. Therefore, the correct answer is A: Its genome consists of dsDNA.
Summary of why other choices are incorrect:
B: Parvovirus B19 is a non-enveloped virus, making choice B incorrect.
C: Parvovirus B19 has a linear ssDNA genome, not segmented, making choice C incorrect.
D: Parvovirus B19 has two structural proteins - VP1 and VP2, making choice D incorrect.
During the skill-building session in microbiology the students need to stain the prepared and fixed sputum smears obtained from a tuberculosis patient. What staining technique should be used in this case?
- A. Gram
- B. Giemsa
- C. Ziehl-Neelsen
- D. Burry
Correct Answer: C
Rationale: The correct staining technique for staining sputum smears from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses a carbol fuchsin stain that specifically stains acid-fast organisms like Mycobacterium tuberculosis. The steps involved include staining with carbol fuchsin, decolorizing with acid-alcohol, counterstaining with methylene blue, and then examining under a microscope. This staining method is crucial for detecting the acid-fast bacilli characteristic of tuberculosis.
Explanation for incorrect choices:
A: Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative, not suitable for acid-fast organisms like Mycobacterium tuberculosis.
B: Giemsa staining is used for detecting parasites and certain types of white blood cells, not specific for acid-fast bacteria.
D: Burry staining is not a recognized staining technique in microbiology for staining acid-fast organisms.
A wound culture from a patient with an infected ulcer revealed Gram-positive rods with terminal spores. What is the most likely causative agent?
- A. Clostridium perfringens
- B. Bacillus anthracis
- C. Clostridium tetani
- D. Bacillus cereus
Correct Answer: A
Rationale: Step-by-step rationale:
1. Gram-positive rods with terminal spores suggest Clostridium genus.
2. Terminal spores are characteristic of Clostridium perfringens.
3. C. perfringens is known to cause wound infections.
4. Therefore, the most likely causative agent is Clostridium perfringens.
Summary:
A: Clostridium perfringens is correct due to its characteristic features and association with wound infections.
B: Bacillus anthracis does not typically form terminal spores.
C: Clostridium tetani causes tetanus, not wound infections.
D: Bacillus cereus does not produce terminal spores like Clostridium perfringens.
A 16-year-old adolescent was vaccinated with DTP. In eight days there was stiffness and pain in the joints, subfebrile temperature, urticarial skin eruption, enlargement of inguinal, cervical lymph nodes and spleen. What kind of allergic reaction is observed?
- A. Immunocomplex
- B. Hypersensitivity of immediate type
- C. Cytoxic
- D. Hypersensitivity of delayed type
Correct Answer: D
Rationale: The correct answer is D: Hypersensitivity of delayed type. The symptoms described occur 5-10 days after exposure to the antigen, consistent with a delayed hypersensitivity reaction. This type of reaction involves T cells and is characterized by cell-mediated immune response, leading to inflammation and tissue damage. Choices A, B, and C are incorrect because they are associated with different mechanisms of allergic reactions. Immunocomplex reactions (choice A) involve antigen-antibody complexes depositing in tissues, immediate hypersensitivity reactions (choice B) involve IgE-mediated mast cell degranulation, and cytotoxic reactions (choice C) involve antibodies targeting specific cells for destruction.