Correct Answer: D

Rationale: The correct answer is D: TCBS. Thiosulfate-citrate-bile salts-sucrose (TCBS) agar is the most selective for Vibrio cholerae due to its high salt content, bile salts, and sucrose. Vibrio cholerae can grow well in alkaline conditions, which are provided by TCBS agar. MacConkey's agar (A) is selective for gram-negative bacteria, but not specifically for Vibrio cholerae. Chocolate agar (B) is a non-selective medium suitable for fastidious organisms. SS agar (C) is selective for Salmonella and Shigella species, not Vibrio cholerae.

Correct Answer: C

Rationale: The correct answer is C because the case specifically mentions "enteropathogenic bacteria and viruses," indicating a focus on these specific microorganisms. Choice A is too broad and includes all bacteria, which is not specified in the case. Choice B mentions opportunistic pathogenic bacteria, which are not necessarily relevant to the case. Choice D specifies colibacilli, which may or may not be relevant to the case, but it is not as specific as choice C which clearly matches the information provided in the case.

Correct Answer: D

Rationale: The correct answer is D: Relenza and Tamiflu. Both Relenza and Tamiflu are anti-influenza drugs that target the neuraminidase enzyme of the influenza virus, thereby inhibiting its replication and spread. Maxi Grip (A) is not an anti-influenza drug, Theraflu (B) contains different active ingredients, and Amantadine and Rimantadine (C) target a different viral protein, M2 ion channel. Therefore, choices A, B, and C are incorrect as they do not specifically target neuraminidase for influenza treatment.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. The presence of Gram-positive cocci in chains suggests a streptococcal infection. Beta-hemolysis indicates the production of a hemolysin that lyses red blood cells, a characteristic of Streptococcus pyogenes. This bacterium is known to cause strep throat and can present with fever and sore throat. Summary: - B: Streptococcus pneumoniae is a common cause of pneumonia but typically appears as lancet-shaped cocci, not in chains. - C: Staphylococcus aureus is a gram-positive cocci in clusters, not chains, and is not typically beta-hemolytic. - D: Enterococcus faecalis is a gram-positive cocci that are part of the normal gut flora and are not typically beta-hemolytic or found in chains.

Correct Answer: A

Rationale: Acyclovir is an antiviral drug used to treat herpes infections, not influenza. Tamiflu, Amantadine, and Relenza are all antiviral drugs commonly used to treat influenza. Acyclovir works by inhibiting the replication of herpes viruses, so it is not effective against the influenza virus. Therefore, the correct answer is A.