A specimen stained by Ozheshko method contains rod-like microorganisms stained blue with round terminal components stained red. What are these components called?

Correct Answer: A

Rationale: The correct answer is A: Spores. In the Ozheshko staining method, spores appear blue with red terminal components. Spores are reproductive structures produced by some bacteria, fungi, and protozoa. Cilia are short, hair-like structures used for movement. Flagella are long, whip-like structures also used for movement. Capsules are outer protective layers surrounding some bacteria. In this case, the description of rod-like microorganisms with blue staining and red terminal components aligns with the characteristics of spores, making it the correct answer.

Correct Answer: B

Rationale: The correct answer is B because retroviruses, including those in the Family Retroviridae, have a capsid consisting of two copies of single-stranded RNA (ssRNA). This is a defining characteristic of retroviruses, which use reverse transcriptase to convert their ssRNA into DNA. This DNA is then integrated into the host cell's genome. Choices A, C, and D are incorrect because Family Retroviridae viruses are not helical non-enveloped viruses (C), they are not helical enveloped viruses (A), and they do not have a complex type of symmetry (D).

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.

Correct Answer: A

Rationale: The correct answer is A because enteropathogenic E. coli (EPEC) have fimbrial adhesins that help them bind to enterocytes in the intestines, leading to colonization and infection. This is a key virulence factor of EPEC. Explanation for why other choices are incorrect: B: EPEC typically cause watery diarrhea in infants, not bloody diarrhea similar to shigellosis. C: EPEC are not part of the normal intestinal flora; they are pathogenic bacteria. D: EPEC are not invasive and do not typically produce enterotoxin; they primarily adhere to the intestinal epithelium.

Correct Answer: D

Rationale: Certainly! The correct answer is D: Pertussis exotoxin. Pertussis toxin primarily affects the respiratory system causing whooping cough. It does not directly target the nervous system like the other toxins listed. Tetanospasmin causes muscle spasms, Diphtheria exotoxin affects the heart and nerves, and Botulinum exotoxin causes paralysis by blocking neurotransmitter release. Therefore, Pertussis exotoxin is the only toxin among the options that does not manifest with neurological symptoms.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Mycobacterium leprae is the correct answer because it is the bacterium responsible for causing leprosy. 2. Neisseria gonorrhoeae causes gonorrhea, not leprosy. 3. Escherichia coli is associated with gastrointestinal infections, not leprosy. 4. Staphylococcus aureus causes various skin infections, but not leprosy. In summary, Mycobacterium leprae is the correct choice because it is the specific bacterium known to cause leprosy, while the other options are associated with different diseases.

Correct Answer: D

Rationale: The correct answer is D: Sporotrichosis. Sporotrichosis is caused by the fungus Sporothrix schenckii, which commonly presents as a subcutaneous infection. In the given case, the presence of a small abscess with yellowish-green pus containing white granules is indicative of sporotrichosis. The histological examination showing drusen of a fungus, plasmatic and xanthome cells, and macrophages further supports the diagnosis of sporotrichosis. Choice A: Actinomycosis is a bacterial infection caused by Actinomyces species, not a fungal infection. Choice B: Aspergillosis is caused by Aspergillus species and typically presents as a pulmonary infection, not a subcutaneous abscess as described in the case. Choice C: Candidosis is caused by Candida species and usually presents as mucocutaneous infections, not a subcutaneous abscess with the

Correct Answer: D

Rationale: Rationale: 1. Mycobacterium tuberculosis, Legionella pneumophila, Brucella melitensis can evade complete phagocytosis. 2. Mycobacterium tuberculosis inhibits phagosome-lysosome fusion. 3. Legionella pneumophila can prevent phagosome maturation. 4. Brucella melitensis can survive and replicate within phagocytes. 5. A + B + C together represent non-complete phagocytosis. Summary: - A, B, C individually cause incomplete phagocytosis. - Only when all three are present together (D) is non-complete phagocytosis observed.

Correct Answer: A

Rationale: Step-by-step rationale for the correct answer (A - Clostridium tetani): 1. The patient has convulsive contractions of facial muscles, indicating tetanus. 2. Isolation of bacteria with terminal endospores that have a drumstick appearance is characteristic of Clostridium tetani. 3. Clostridium tetani produces tetanospasmin toxin causing muscle spasms. 4. Therefore, the correct answer is Clostridium tetani (A). Summary of why other choices are incorrect: B: Clostridium botulinum causes botulism, not tetanus. C: Clostridium perfringens causes gas gangrene, not tetanus. D: Bacillus anthracis causes anthrax, not tetanus.