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Which bacteria is a common cause of bacterial meningitis?
- A. Neisseria meningitidis
- B. Streptococcus pneumoniae
- C. Haemophilus influenzae
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae are all common causes of bacterial meningitis. Neisseria meningitidis is often associated with outbreaks in community settings. Streptococcus pneumoniae is a leading cause of bacterial meningitis in adults. Haemophilus influenzae used to be a common cause in children before the introduction of the Hib vaccine. Therefore, since all three bacteria are known to cause bacterial meningitis, the correct answer is D. Choices A, B, and C are incorrect because each bacteria individually can cause bacterial meningitis, making "All of the above" the correct comprehensive answer.
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A dentist has detected symptoms of parodontosis in a patient. What antiprotozoal drug should be prescribed?
- A. Metronidazole
- B. Levamisole
- C. Griseofulvin
- D. Mykoseptin
Correct Answer: A
Rationale: The correct answer is A: Metronidazole. Parodontosis is a condition caused by bacterial infection, not protozoal infection. Metronidazole is an effective antibiotic commonly used to treat bacterial infections in the oral cavity, including those associated with parodontosis. Levamisole is an anthelmintic drug used to treat parasitic worm infections, not suitable for parodontosis. Griseofulvin is an antifungal medication used for fungal infections, not indicated for parodontosis. Mykoseptin is not a recognized drug and is likely a distractor. Therefore, based on the bacterial nature of parodontosis, Metronidazole is the appropriate choice.
A smear prepared from material obtained from patient with suspected diphtheria contains yellow bacilli with blue grains at their ends. What staining was used in this case?
- A. Ziehl-Nielsen
- B. Kozlovsky
- C. Romanovsky
- D. Loefler
Correct Answer: D
Rationale: The correct answer is D: Loefler. This staining method is used for identifying Corynebacterium diphtheriae, the causative agent of diphtheria. It involves using methylene blue and basic fuchsin to stain the bacteria. The yellow bacilli with blue grains at their ends indicate the characteristic appearance of C. diphtheriae when stained using the Loefler method.
Choice A: Ziehl-Nielsen is used for acid-fast bacteria like Mycobacterium tuberculosis.
Choice B: Kozlovsky is not a standard staining method in microbiology.
Choice C: Romanovsky is used for blood smears to identify malaria parasites.
For the viral structure of rubella virus is true that
- A. does not have glycoprotein spikes
- B. does not have an envelope
- C. is ssDNA virus
- D. has icosahedral type of symmetry
Correct Answer: D
Rationale: The correct answer is D because the rubella virus has icosahedral symmetry, meaning it has a spherical shape with 20 equilateral triangular faces. This symmetry is common in many viruses and allows for efficient packaging of genetic material.
Choice A is incorrect because the rubella virus does have glycoprotein spikes on its surface. These spikes help the virus attach to host cells.
Choice B is incorrect because the rubella virus does have an envelope derived from the host cell membrane. This envelope plays a role in viral entry into host cells.
Choice C is incorrect because the rubella virus is an ssRNA virus, not ssDNA. Its genetic material is single-stranded RNA, not DNA.
In summary, the rubella virus has icosahedral symmetry and possesses glycoprotein spikes, an envelope, and ssRNA genetic material, making choices A, B, and C incorrect.
A patient with an abscess had Gram-positive cocci in clusters isolated from a wound culture. The organism was catalase-positive and coagulase-positive. What is the likely causative agent?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: Step-by-step rationale:
1. Gram-positive cocci in clusters suggest Staphylococcus or Streptococcus.
2. Catalase-positive and coagulase-positive narrow it down to Staphylococcus.
3. Staphylococcus aureus is catalase-positive and coagulase-positive.
Therefore, the likely causative agent is Staphylococcus aureus.
Summary:
A: Correct - Staphylococcus aureus fits all the characteristics.
B: Incorrect - Staphylococcus epidermidis is catalase-negative and coagulase-negative.
C: Incorrect - Streptococcus pyogenes is catalase-negative and coagulase-negative.
D: Incorrect - Enterococcus faecalis is catalase-negative and coagulase-negative.
The ability of Clostridium tetani to produce exotoxins is encoded by?
- A. genes with chromosomal location
- B. clostridium tetani is not capable of producing exotoxins, it has only endotoxin activity
- C. genes with plasmid location
- D. chromosomal and plasmid location
Correct Answer: C
Rationale: The correct answer is C: genes with plasmid location. Clostridium tetani produces exotoxins through genes located on plasmids. Plasmids are extrachromosomal genetic elements that carry additional genes. These genes encode for the production of exotoxins in Clostridium tetani. Choices A, B, and D are incorrect because Clostridium tetani does produce exotoxins, it does not have only endotoxin activity, and the genes responsible for exotoxin production are located on plasmids, not solely on the chromosome or both chromosome and plasmid.