Which of the following pathogenic factors is typical for the virulent strains of Listeria monocytogenes

Correct Answer: D

Rationale: The correct answer is D because virulent strains of Listeria monocytogenes exhibit multiple pathogenic factors. A: They do not have endotoxin-like substances, so this is incorrect. B: They are indeed facultative intracellular bacteria, aiding in their ability to survive and replicate inside host cells. C: They produce hemolysin, which helps them lyse red blood cells. Therefore, the correct answer is D, as all of the above statements are true for virulent strains of Listeria monocytogenes.

Correct Answer: D

Rationale: The correct answer is D because Borrelia burgdorferi cannot be detected with Giemsa stain. Giemsa stain is commonly used to visualize blood smears for malaria parasites but is not effective for Borrelia burgdorferi detection. A: Borrelia burgdorferi can be cultivated on blood agar - This is correct. Borrelia burgdorferi can be grown in culture on a special medium like Barbour-Stoenner-Kelly (BSK) agar. B: Borrelia burgdorferi is flexible, motile spirochete - This is correct. Borrelia burgdorferi is a spiral-shaped bacterium that moves using a corkscrew motion. C: Borrelia burgdorferi is transmitted by arthropods- ticks - This is correct. Borrelia burgdorferi is primarily transmitted to humans through the bite of infected ticks, particularly Ixodes

Correct Answer: C

Rationale: Rationale: 1. Shigella invades and multiplies within the intestinal epithelial cells, causing inflammation and tissue damage locally. 2. It does not spread systemically, unlike Yersinia enterocolitica and Listeria monocytogenes. 3. Shigella's pathogenesis is focused on invasion and multiplication at the site of infection, leading to symptoms of dysentery. 4. Yersinia enterocolitica and Listeria monocytogenes can disseminate beyond the gastrointestinal tract, causing systemic infections. Summary: - A (Yersinia enterocolitica) and B (Listeria monocytogenes) are incorrect as they can generalize the infectious process. - C (Shigella) is correct as it mainly involves invasion and intraepithelial multiplication without spreading systemically.

Correct Answer: C

Rationale: Rationale: 1. Candida is a fungus commonly isolated from clinical specimens. 2. Sabouraud agar is the most suitable medium for Candida due to its low pH and high dextrose content. 3. Low pH inhibits bacterial growth, while dextrose promotes fungal growth. 4. Zeisler media, Chocolate agar, and Muller-Hinton agar are not specific for fungal isolation. Summary: - Zeisler media is used for anaerobic bacteria. - Chocolate agar is used for fastidious organisms like Haemophilus. - Muller-Hinton agar is for antibiotic susceptibility testing, not fungal isolation.

Correct Answer: B

Rationale: The correct answer is B: Aminoglycosides. Aminoglycosides are antibiotics that act by binding to the 30S ribosomal subunit, disrupting protein synthesis in bacteria. This interaction affects the ribosomes directly, leading to inhibition of bacterial protein production. Penicillins (A) work by inhibiting cell wall synthesis, Sulfonamides (C) target folic acid synthesis, and Quinolones (D) inhibit DNA gyrase. These mechanisms do not directly affect the ribosomes, making them incorrect choices in this context.