Nokea
The main virulence factor of Neisseria meningitidis is?
- A. The polysaccharide capsule
- B. The beta lactamase
- C. The erythrogenic toxin
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: The polysaccharide capsule. The capsule of Neisseria meningitidis plays a crucial role in its virulence by preventing phagocytosis, allowing the bacteria to evade the host's immune system. This leads to increased survival and colonization in the host.
Choice B: The beta lactamase is incorrect because it is an enzyme that breaks down beta-lactam antibiotics and does not directly contribute to the virulence of Neisseria meningitidis.
Choice C: The erythrogenic toxin is incorrect as this toxin is produced by Streptococcus pyogenes, not Neisseria meningitidis.
Choice D: None of the above is incorrect as the polysaccharide capsule is indeed a key virulence factor of Neisseria meningitidis.
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A mercury-containing compound used as a preservative in vaccines is:
- A. analgesic
- B. EDTA
- C. codeine
- D. thimerosal
Correct Answer: D
Rationale: The correct answer is D: thimerosal. Thimerosal is a mercury-containing compound used as a preservative in vaccines. It helps prevent contamination and growth of bacteria and fungi in multi-dose vials. Choice A, analgesic, refers to pain relievers, not preservatives. Choice B, EDTA, is a chelating agent used to bind metal ions and is not a preservative. Choice C, codeine, is an opioid pain medication and not a preservative used in vaccines. Thimerosal is the correct answer as it specifically fits the description of a mercury-containing compound used in vaccines.
During a microbiology session, students observed flagellated protozoa with an undulating membrane in vaginal discharge samples. What is the causative agent?
- A. Trichomonas vaginalis
- B. Giardia lamblia
- C. Trypanosoma brucei
- D. Leishmania donovani
Correct Answer: A
Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a flagellated protozoa that causes the sexually transmitted infection trichomoniasis. The presence of an undulating membrane in vaginal discharge samples is characteristic of Trichomonas vaginalis. Giardia lamblia causes gastrointestinal illness, not vaginal infections. Trypanosoma brucei causes African sleeping sickness transmitted by tsetse flies. Leishmania donovani causes visceral leishmaniasis transmitted by sandflies.
Bacteria associated with hospital-acquired infections:
- A. Streptococcus pneumoniae
- B. Pseudomonas aeruginosa
- C. Vibrio cholerae
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is commonly associated with hospital-acquired infections due to its ability to survive in hospital environments, resist antibiotics, and infect immunocompromised patients. Streptococcus pneumoniae (choice A) is more commonly associated with community-acquired pneumonia. Vibrio cholerae (choice C) causes cholera, a waterborne disease, and is not typically associated with hospital-acquired infections. Choice D is incorrect because Pseudomonas aeruginosa is indeed associated with hospital-acquired infections.
A patient with bacterial endocarditis had Gram-positive cocci in chains isolated from blood cultures. The organism was catalase-negative. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Enterococcus faecalis
- D. Micrococcus luteus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This is because Streptococcus pyogenes is a Gram-positive cocci in chains bacterium that is catalase-negative, making it the most likely causative agent in this scenario. Streptococcus pyogenes is a common pathogen causing bacterial endocarditis.
Summary of other choices:
B: Staphylococcus aureus is a Gram-positive cocci bacterium but is catalase-positive, so it is unlikely in this case.
C: Enterococcus faecalis is a Gram-positive cocci bacterium, but it is catalase-negative, which is not consistent with the given information.
D: Micrococcus luteus is a Gram-positive cocci bacterium but is catalase-positive, making it an unlikely causative agent.
Which one is an example of an immunomodulator
- A. Pentaxim
- B. Hexacima
- C. Gamma-interferon
- D. Rifampin
Correct Answer: C
Rationale: Step-by-step rationale for why C is correct:
1. Immunomodulators regulate the immune response.
2. Gamma-interferon is a cytokine that enhances immune function.
3. It helps fight infections and regulate inflammation.
4. Pentaxim and Hexacima are combination vaccines.
5. Rifampin is an antibiotic, not an immunomodulator.
Summary:
- A and B are combination vaccines.
- D is an antibiotic.
- C is the correct answer as gamma-interferon is an immunomodulator that regulates the immune response.