The most important virulence factor of Bordetella pertussis is:

Correct Answer: B

Rationale: The correct answer is B: pertussis toxin. This toxin is the most important virulence factor of Bordetella pertussis because it plays a key role in causing the characteristic symptoms of whooping cough. Pertussis toxin interferes with the host's immune response, leading to inflammation and tissue damage in the respiratory tract. The other choices (A: the flagellum, C: P fimbriae, D: mannose-resistant adhesins) are important for bacterial attachment and colonization, but they do not directly contribute to the severity of the disease like pertussis toxin does.

Correct Answer: D

Rationale: Interferon delta is not a known type of interferon, making choice D incorrect. Interferon beta is indeed produced by fibroblasts (choice A), interferon alpha by leukocytes (choice B), and interferon gamma by lymphocytes (choice C). Each type of interferon is produced by specific cells in the immune system, contributing to the body's defense against viruses and other pathogens.

Correct Answer: B

Rationale: The correct answer is B because filoviruses, such as Ebola virus, require investigation in specifically equipped laboratories with high biological protection due to their high pathogenicity and risk of transmission. This is essential for ensuring the safety of researchers and preventing outbreaks. A: This is incorrect as filoviruses are not the most common cause of gastroenteritis; they primarily cause severe hemorrhagic fevers. C: Filoviruses are not widespread; they are typically confined to specific regions during outbreaks. D: Mass immunization is not used for filoviruses as there is no established vaccine for general prophylaxis.

Correct Answer: A

Rationale: Rationale for correct answer (A: Escherichia coli): 1. Endo agar selects for Gram-negative bacteria. 2. Red colonies on Endo agar indicate lactose fermentation, characteristic of E. coli. 3. E. coli is a common cause of pneumonia, especially in immunocompromised patients. Summary of why other choices are incorrect: - B: Klebsiella pneumoniae: Typically forms mucoid colonies on agar. - C: Pseudomonas aeruginosa: Produces characteristic greenish-blue colonies on agar. - D: Proteus mirabilis: Does not typically ferment lactose, so would not produce red colonies on Endo agar.

Correct Answer: A

Rationale: The correct answer is A: Clostridium perfringens. This bacterium is a Gram-positive rod that forms chains and produces gas due to its ability to ferment carbohydrates. It is also spore-forming, which helps it survive harsh conditions. Clostridium perfringens is commonly associated with severe tissue infections and gas gangrene. Choice B: Bacillus anthracis is also a spore-forming Gram-positive rod but is not typically associated with gas production or severe tissue infections. Choice C: Clostridium tetani is a spore-forming bacterium that causes tetanus, not severe tissue infections with gas production. Choice D: Pseudomonas aeruginosa is a Gram-negative bacterium and does not fit the description provided in the question.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Marburg virus is named after the German city Marburg where it was first identified in 1967. 2. Chikungunya virus is named after a village in Tanzania. 3. Measles virus got its name from the Middle English word "maselen" meaning "many little spots". 4. Epstein-Barr virus is named after Michael Epstein and Yvonne Barr, who discovered it. Summary: B is correct as it is directly named after the city of its discovery. A, C, and D are incorrect as they are named after other locations, characteristics, or discoverers.

Correct Answer: C

Rationale: Rationale: Metronidazole is the drug of choice for systemic amebiasis due to its high efficacy against Entamoeba histolytica. It has good tissue penetration and can treat intestinal, liver, and lung involvement. Quiniofone (A) has limited use and is not recommended for amebiasis. Enteroseptol (B) is not effective against systemic amebiasis. Tetracycline (D) is not the first-line treatment for amebiasis and has limited efficacy against Entamoeba histolytica.

Correct Answer: A

Rationale: The correct answer is A: Sabouraud's peptone agar. This agar is specifically designed for the isolation of yeast and molds due to its low pH and high sugar content, creating an environment conducive for their growth. Yeast-like fungi thrive in this selective medium, while inhibiting the growth of bacteria and other contaminants. Summary: - Sabouraud's peptone agar is ideal for cultivating yeast-like fungi. - Endo agar is used for isolation of gram-negative bacteria, not fungi. - Milk-salt agar is used for lactobacilli and streptococci, not fungi. - Meat infusion agar is a general-purpose medium for cultivation of a wide range of microorganisms, not specifically for yeast-like fungi.

Correct Answer: D

Rationale: The most probable diagnosis is D: Tularemia. Tularemia is a bacterial infection caused by Francisella tularensis. The symptoms described align with tularemia, such as pain in axillary area, fever, shaky gait, coated tongue, frequent pulse, painful lymphatic nodules, and erythematous skin over nodules. The key features pointing towards tularemia are the presence of lymphadenitis in the axillary area and the erythematous, glistering skin over the nodules, which are characteristic of ulceroglandular tularemia. Bubonic plague (A) presents with painful, swollen lymph nodes called buboes but typically lacks the erythematous skin findings. Acute purulent lymphadenitis (B) usually presents with pus-filled lymph nodes but does not typically cause shaky gait or coated tongue. Lymphogranulomatosis (C) is a term for Hodgkin's lymphoma, which does not