A healthy man is in a region with high risk of catching malaria. What drug should be administered for individual chemoprophylaxis of malaria?

Correct Answer: A

Rationale: The correct answer is A: Chingamin (also known as Chloroquine). Chingamin is the drug of choice for chemoprophylaxis of malaria in regions with high risk. It is effective against Plasmodium falciparum, the most common malaria parasite. Chingamin is well-tolerated, affordable, and has a long track record of use. Sulfalen (Choice B) is not commonly used for malaria prophylaxis. Tetracycline (Choice C) is not recommended for malaria prophylaxis due to poor efficacy and resistance development. Metronidazole (Choice D) is not effective against malaria parasites.

Correct Answer: A

Rationale: The correct answer is A: Gram-negative stain. Pseudomonas aeruginosa is a gram-negative bacterium, as indicated by the bluish-green pus color. This bacterium has an outer membrane that retains the crystal violet stain, making it appear pink/red after the counterstain with safranin in Gram staining. The other choices are incorrect because Pseudomonas aeruginosa does not typically form spores (B), has a rod-shaped morphology rather than a coccal form (C), and does not exhibit cell pairing (D).

Correct Answer: A

Rationale: The correct answer is A: Aspergillosis and candidiasis. Galactomannan is a polysaccharide found in Aspergillus cell walls and is detected in patients with invasive aspergillosis. Free mannan is a polysaccharide found in Candida cell walls and is detected in patients with candidiasis. Therefore, detection of galactomannan and free mannan is specific for diagnosing Aspergillosis and candidiasis. Choices B, C, and D are incorrect as HIV infection, syphilis, and leptospirosis do not involve the detection of galactomannan or free mannan for diagnosis.

Correct Answer: B

Rationale: The correct answer is B: IgM. IgM is the first antibody synthesized by the infant soon after birth. It is produced by B cells in response to initial exposure to antigens. IgA is mainly found in mucosal areas, IgG is transferred from mother to fetus, and IgD functions in the early stages of B cell development. Therefore, IgM is the most suitable choice as the antibody synthesized by the infant soon after birth.

Correct Answer: C

Rationale: The correct answer is C: Reaction type GRUBER. Agglutination reaction in GRUBER involves the clumping of particles due to specific antibodies binding to antigens on the surface. This reaction is commonly used in blood typing and serology tests. A: Western blot is a technique used to detect specific proteins in a sample, not related to agglutination. B: ELISA is an enzyme-linked immunosorbent assay used to detect antibodies or antigens, not based on agglutination. D: Ascoli ring test is a method to detect the presence of DNA in a sample, not related to agglutination.

Correct Answer: C

Rationale: The correct answer is C: Endospore. Endospores are dormant, tough, and non-reproductive structures formed by certain bacteria as a response to unfavorable conditions. They help bacteria survive harsh environments such as extreme temperatures, desiccation, and exposure to harmful chemicals. The other choices, Flagella (A), Capsule (B), and Pili (D), do not directly contribute to bacterial survival in adverse conditions. Flagella aid in bacterial movement, capsules provide protection from immune system attacks, and pili are involved in attachment to surfaces or other cells. Endospores are specifically designed for survival during unfavorable conditions, making them the correct choice in this scenario.

Correct Answer: B

Rationale: The correct answer is B because in immune reactions, a large lattice is formed when antigens and antibodies are in optimal proportion. This optimal ratio allows for the formation of a strong antigen-antibody complex, leading to the aggregation of immune complexes into large lattice structures. When antibodies are in excess (choice A), there may not be enough antigens to form a stable lattice. Similarly, when antigens are in excess (choice C), there may be insufficient antibodies to form a strong lattice. Choice D is incorrect because the optimal proportion of antigens and antibodies is crucial for the formation of large lattices in immune reactions.

Correct Answer: B

Rationale: The correct answer is B: microaerophiles. These bacteria require oxygen to grow, but only at low concentrations as higher levels can be toxic. They possess enzymes to deal with reactive oxygen species. Obligate aerobes (A) require oxygen for growth, obligate anaerobes (C) cannot survive in the presence of oxygen, and aerotolerant anaerobes (D) can tolerate oxygen but do not use it for growth.

Correct Answer: B

Rationale: The correct answer is B: Adhesion. Pili are bacterial appendages that help bacteria adhere to surfaces. This is important for colonization and biofilm formation. Choice A (Chemotaxis) is incorrect because chemotaxis is the movement of bacteria in response to chemical stimuli, not the function of pili. Choice C (Nutrient acquisition) is incorrect because pili are not directly involved in obtaining nutrients. Choice D (None of the above) is incorrect as pili do serve a specific purpose, which is adhesion.