Nokea
Which of the following statements about family Arenaviridae is true?
- A. Cannot be isolated from clinical materials due to lack of biological models and diagnosis is only serological
- B. Replicate in the nucleus of the infected cells
- C. Lymphocytic choriomeningitis virus belongs to the family
- D. The only host is the human
Correct Answer: C
Rationale: The correct answer is C because lymphocytic choriomeningitis virus belongs to the family Arenaviridae. This virus is a well-known member of the Arenaviridae family and is associated with various diseases. Option A is incorrect as Arenaviruses can be isolated from clinical materials using suitable methods. Option B is incorrect because Arenaviruses replicate in the cytoplasm, not the nucleus. Option D is incorrect as Arenaviruses can infect various hosts, not just humans. Therefore, the statement that lymphocytic choriomeningitis virus belongs to the family Arenaviridae is true.
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Microscopic analysis of a smear stained by Ziehl-Neelsen method revealed bright red bacilli. What microorganism is being tested for?
- A. Mycobacterium tuberculosis
- B. Staphylococcus aureus
- C. Clostridium tetani
- D. Escherichia coli
Correct Answer: A
Rationale: The Ziehl-Neelsen stain is specific for acid-fast bacteria like Mycobacterium tuberculosis. The bright red bacilli seen in the smear indicate the presence of acid-fast organisms, which is characteristic of Mycobacterium tuberculosis. Staphylococcus aureus, Clostridium tetani, and Escherichia coli are not acid-fast bacteria and would not be stained red using the Ziehl-Neelsen method. Therefore, the correct answer is A: Mycobacterium tuberculosis.
Which of the following is a characteristic feature of Gram-positive bacteria?
- A. Outer membrane
- B. Thin peptidoglycan layer
- C. Thick peptidoglycan layer
- D. Presence of LPS
Correct Answer: C
Rationale: The correct answer is C: Thick peptidoglycan layer. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain during Gram staining. This thick layer is a key characteristic feature that helps differentiate Gram-positive bacteria from Gram-negative bacteria.
Rationale:
1. Gram-positive bacteria retain the crystal violet stain due to their thick peptidoglycan layer.
2. This thick layer provides structural support and protection to the cell.
3. Gram-positive bacteria lack an outer membrane, which is a feature of Gram-negative bacteria (Choice A).
4. Thin peptidoglycan layer is a characteristic of Gram-negative bacteria, not Gram-positive (Choice B).
5. Presence of LPS (lipopolysaccharide) is a feature of Gram-negative bacteria, not Gram-positive (Choice D).
In summary, the presence of a thick peptidoglycan layer is a characteristic feature of Gram-positive
A patient complains of acute spastic abdominal pain, frequent urge to defecate, liquid bloody feces with mucus. Laboratory analysis of fecal smear revealed inconstant in shape organisms with erythrocyte. What is the most likely diagnosis?
- A. Amebiasis.
- B. Lambliasis.
- C. Schistosomiasis.
- D. Intestinal trichomoniasis.
Correct Answer: A
Rationale: The correct answer is A: Amebiasis. Amebiasis is caused by the parasite Entamoeba histolytica, presenting with symptoms like acute abdominal pain, bloody diarrhea with mucus, and inconstant shape organisms seen in fecal smear. The presence of erythrocytes supports the diagnosis due to the parasite's ability to invade intestinal mucosa causing bleeding. Choice B (Lambliasis) presents with different symptoms like steatorrhea and fatigue. Choice C (Schistosomiasis) is mainly associated with liver and urinary symptoms. Choice D (Intestinal trichomoniasis) commonly presents with watery diarrhea and does not typically cause bloody stools. Therefore, based on the patient's symptoms and fecal smear findings, Amebiasis is the most likely diagnosis.
During the staining of sputum smear of a patient with suspected croupous pneumonia the following reactives and stainers were used: gentian violet solution, Lugol's solution, 960 spiritus and water fuchsin. What method of staining is used in this case?
- A. Leffler's
- B. Gram's
- C. Ziehl-Neelsen's
- D. Neisser's
Correct Answer: B
Rationale: The correct answer is B: Gram's staining method. The rationale for this is as follows: Gentian violet and Lugol's solution are used as primary and mordant stains in the Gram's staining method. Spiritus 960 is used as a decolorizer, and water fuchsin is used as a counterstain. This staining method is commonly used in microbiology to differentiate bacteria into Gram-positive and Gram-negative based on their cell wall characteristics.
A: Leffler's staining method is used for the identification of diphtheria bacilli.
C: Ziehl-Neelsen's staining method is used for acid-fast bacteria like Mycobacterium tuberculosis.
D: Neisser's staining method is used for the identification of Neisseria species.
In summary, the use of specific reactives and stainers in the question indicates the application of the Gram's staining method for bacterial differentiation.
Bacterial replication is accomplished primarily by:
- A. mitosis
- B. meiosis
- C. cytokinesis
- D. binary fission
Correct Answer: D
Rationale: Binary fission is the correct answer for bacterial replication because it is the process by which bacteria divide into two identical daughter cells. During binary fission, the bacterial cell replicates its DNA, forms a septum dividing the cell into two, and eventually splits into two daughter cells. This process is specific to prokaryotic cells such as bacteria and is different from mitosis and meiosis, which are processes specific to eukaryotic cells. Cytokinesis is the final step of cell division in both eukaryotes and prokaryotes, but it is not the primary mechanism of bacterial replication.