The white pulp and red pulp are part of which immune organ:

Correct Answer: C

Rationale: The correct answer is C: Spleen. The white pulp of the spleen contains lymphocytes that help in immune responses. The red pulp filters blood and removes old or damaged red blood cells. The thymus (A) is responsible for T cell maturation, lymph nodes (B) filter lymph, and lymphoid tissue (D) includes various lymphoid organs but does not specifically refer to the spleen's distinct white and red pulp structure. Thus, the spleen is the only organ among the choices that has both white and red pulp components essential for immune functions.

Correct Answer: A

Rationale: Step 1: Streptococcus pyogenes is commonly known as Group A Streptococcus, which is the primary bacteria responsible for causing strep throat. Step 2: Staphylococcus aureus is not typically associated with strep throat but can cause skin infections and other illnesses. Step 3: Neisseria gonorrhoeae is the bacteria responsible for gonorrhea, a sexually transmitted infection, not strep throat. Step 4: Clostridium tetani causes tetanus, a bacterial infection that affects the nervous system and is not related to strep throat.

Correct Answer: B

Rationale: Step-by-step rationale for choice B being correct: 1. The conclusion should be based on evidence or observations. 2. "Doubtful" suggests uncertainty, indicating lack of definitive safety. 3. Choice A is too absolute without considering potential risks. 4. Choice C uses extreme language without proper evidence. 5. Choice D is overly definitive without considering varying levels of contamination. Therefore, choice B is the most reasonable conclusion.

Correct Answer: C

Rationale: The correct answer is C: Obligate anaerobes cannot tolerate oxygen. They lack the enzymes needed to detoxify reactive oxygen species generated in the presence of oxygen. This makes them unable to survive in oxygen-rich environments. Choice A is incorrect because obligate anaerobes do not require oxygen to survive. Choice B is incorrect because obligate anaerobes specifically require the absence of oxygen. Choice D is incorrect because obligate anaerobes cannot even tolerate low levels of oxygen.

Correct Answer: B

Rationale: The correct answer is B: Trimethoprim. Trimethoprim is a folate antagonist that inhibits dihydrofolate reductase, an enzyme essential for folate metabolism in bacteria. This disrupts bacterial DNA synthesis, leading to bacteriostatic effects. Methyl Penicillin (A) is a beta-lactam antibiotic that interferes with bacterial cell wall synthesis. Vancomycin (C) inhibits cell wall synthesis by binding to D-Ala-D-Ala terminus of cell wall precursors. Gentamicin (D) inhibits bacterial protein synthesis by binding to the 30S subunit of the bacterial ribosome.

Correct Answer: B

Rationale: Step 1: Adenoviruses are known to have icosahedral capsids, not helical. Step 2: Helical capsids are typically found in viruses like tobacco mosaic virus. Step 3: Therefore, the statement that adenoviruses have helical capsids is FALSE. Summary: A is incorrect as adenoviruses do not have helical capsids. C is incorrect as there is no situation where adenoviruses have helical capsids. D is incorrect as there is a clear correct answer, which is B.

Correct Answer: D

Rationale: The correct answer is D, All of the above. Clostridium botulinum produces botulinum toxin causing botulism, Vibrio cholerae produces cholera toxin leading to severe diarrhea, and certain strains of Escherichia coli produce toxins causing gastrointestinal illness. Each bacterium has specific exotoxins that can result in severe gastrointestinal symptoms. Therefore, all three choices are correct in producing exotoxins that can cause severe gastrointestinal illness.

Correct Answer: D

Rationale: The correct answer is D: epidermolytic toxin. This toxin specifically targets the epidermis, leading to exfoliation seen in scalded skin syndrome (SSS). Hemolysis (A) refers to the destruction of red blood cells, not relevant to SSS. Enterotoxins (B) cause food poisoning, not SSS. Leucocidins (C) target white blood cells, not pertinent to SSS. Therefore, the epidermolytic toxin (D) is the correct choice for causing SSS.

Correct Answer: A

Rationale: The correct answer is A: Late congenital syphilis. The symptoms described align with late congenital syphilis, which includes saddle nose, high-arched palate, natiform skull, peg-shaped incisors, and notched cutting edge. Lymph nodes not being affected is also consistent with late congenital syphilis. Early congenital syphilis (B) typically presents with more severe symptoms at birth or shortly after. Tertiary syphilis (C) usually occurs years after initial infection and presents with different symptoms. Fluorosis (D) is caused by excessive fluoride intake and does not match the symptoms described.