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Microscopy of a smear from a patient with foul-smelling diarrhea revealed large ciliated protozoa with a kidney-shaped macronucleus. What is the diagnosis?
- A. Balantidiasis
- B. Giardiasis
- C. Amoebiasis
- D. Trichomoniasis
Correct Answer: A
Rationale: The correct diagnosis is A: Balantidiasis. The presence of large ciliated protozoa with a kidney-shaped macronucleus is characteristic of Balantidium coli, the causative agent of balantidiasis. The ciliated trophozoites of Balantidium coli are unique compared to the other choices. Giardiasis is caused by Giardia lamblia, which has flagella and not cilia. Amoebiasis is caused by Entamoeba histolytica, which lacks cilia. Trichomoniasis is caused by Trichomonas vaginalis, which also lacks cilia. Therefore, based on the specific morphology described, the correct diagnosis is Balantidiasis.
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For the structure of rubella virus, it is true that
- A. has icosahedral type of symmetry
- B. is ssDNA virus
- C. does not have an envelope
- D. does not have glycoprotein spikes
Correct Answer: A
Rationale: Step 1: Rubella virus belongs to the Togaviridae family, which typically exhibits icosahedral symmetry.
Step 2: Icosahedral symmetry refers to a structure with 20 equilateral triangular faces, which is characteristic of many viruses, including rubella.
Step 3: Therefore, choice A is correct as rubella virus indeed has icosahedral type of symmetry.
Summary:
- Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA.
- Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane.
- Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface.
The correct descending order of taxonomic categories is
- A. species, domain, phylum, kingdom, order, division, class, genus
- B. domain, kingdom, phylum, class, family, order, genus, species
- C. domain, kingdom, phylum, class, order, family, genus, species
- D. kingdom, domain, phylum, order, class, family, genus, species
Correct Answer: C
Rationale: The correct descending order of taxonomic categories is domain, kingdom, phylum, class, order, family, genus, species. This hierarchical classification system helps organize and categorize living organisms based on their shared characteristics and evolutionary relationships.
Explanation:
- Domain is the broadest category, representing the highest level of classification.
- Kingdom further divides organisms into major groups based on similar characteristics.
- Phylum, class, order, family, and genus successively narrow down the classification based on more specific shared characteristics.
- Species is the most specific category, representing individual organisms capable of interbreeding.
Summary of other choices:
A: Incorrect as it has the incorrect order of phylum, kingdom, and division.
B: Incorrect as it has the incorrect order of family and species.
D: Incorrect as it has the incorrect order of domain, kingdom, and class.
A child is ill with diphtheria. A smear of the affected mucous membrane revealed blue rods with thickenings at the poles. What staining method was used?
- A. Neisser
- B. Gram
- C. Ziehl-Neelsen
- D. Loeffler
Correct Answer: A
Rationale: The correct answer is A: Neisser staining method. Neisser staining method is used to stain diphtheria bacilli, which appear as blue rods with thickenings at the poles. The rationale is that Neisser staining specifically targets and highlights the characteristics of the diphtheria bacilli.
Incorrect choices:
B: Gram staining is not specific for diphtheria bacilli and does not show the characteristic blue rods with thickenings at the poles.
C: Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for diphtheria bacilli.
D: Loeffler staining is used for diphtheria bacilli but does not produce blue rods with thickenings at the poles as seen in this case.
Which of the following does NOT refer to viruses
- A. cell-free infectious living systems
- B. obligate intracellular parasites
- C. they have either DNA or RNA as genetic material
- D. they are not sensitive to interferon
Correct Answer: D
Rationale: The correct answer is D because viruses are sensitive to interferon, a natural defense mechanism of the body against viral infections. Interferon helps to inhibit viral replication.
A: Viruses are cell-free infectious particles, not living systems.
B: Viruses are obligate intracellular parasites as they require host cells to replicate.
C: Viruses can have either DNA or RNA as genetic material, which is a characteristic feature.
While studying a microslide obtained from the punctuate of a regional lymph node and stained by Romanovsky-Giemsa method a physician revealed some light pink thin microorganisms with 12-14 regular spiral coils and pointed ends, up to 10-13 micrometer long. This might be the causative agent of the following disease:
- A. Syphilis
- B. Trypanosomiasis
- C. Leptospirosis
- D. Relapsing fever
Correct Answer: D
Rationale: The correct answer is D: Relapsing fever. The description matches Borrelia species, the causative agent of relapsing fever. The thin, spiral-shaped microorganisms with pointed ends and specific length are characteristic of Borrelia. The number of coils and size mentioned also align with Borrelia morphology. Relapsing fever is transmitted by tick bites and manifests as recurring febrile episodes.
Incorrect choices:
A: Syphilis - Syphilis is caused by Treponema pallidum, which is not spiral-shaped.
B: Trypanosomiasis - Trypanosomiasis is caused by Trypanosoma species, which are not spiral-shaped.
C: Leptospirosis - Leptospirosis is caused by Leptospira species, which are not spiral-shaped and do not match the specific description provided.