Poxviruses are largest viruses, almost visible on light microscope

Correct Answer: A

Rationale: The correct answer is A: TRUE. Poxviruses are indeed the largest viruses known, ranging from 200-450 nm in size, which is close to the resolution limit of a light microscope. This makes them almost visible under a light microscope. Explanation: 1. Poxviruses have complex structures and are among the largest viruses. 2. Light microscopes have a resolution limit of around 200 nm. 3. Poxviruses fall within the size range that is close to the resolution limit of a light microscope. 4. Therefore, poxviruses are almost visible under a light microscope. Summary: Choice B is incorrect because poxviruses are indeed large enough to be almost visible under a light microscope. Choice C is incorrect as it implies uncertainty, but poxviruses are consistently close to the resolution limit of a light microscope. Choice D is incorrect as the size of poxviruses being almost visible under a light microscope is a factual statement, not dependent

Correct Answer: C

Rationale: The correct answer is C: To perform serodiagnostics of tuberculosis. Rationale: The negative reaction to the Mantoux test indicates absence of TB infection. Performing serodiagnostics will further confirm the absence of active infection. This is important to rule out TB before considering vaccination or isolation measures. Summary: A: BCG vaccination is not necessary as the boy shows a negative reaction to the Mantoux test. B: Repeating the test in a month is unnecessary as the initial test already showed a negative reaction. D: Isolating the boy is not warranted as there is no evidence of active TB infection.

Correct Answer: D

Rationale: The correct answer is D: Thin mobile bacillus with central spore. This is because the causative agent of botulism, Clostridium botulinum, is a gram-positive bacillus that typically appears as a thin rod-shaped bacterium with a central endospore. This characteristic morphology is essential in the identification of Clostridium botulinum. A: Gram-positive bacillus with subterminal spore - This is incorrect as Clostridium botulinum typically has a central endospore, not a subterminal one. B: Thick gram-positive non-spore-forming bacillus - This is incorrect as Clostridium botulinum forms endospores, although they are not thick. C: Gram-positive bacillus with terminal spore - This is incorrect as the spore of Clostridium botulinum is typically central, not terminal.

Correct Answer: A

Rationale: Step 1: Understand haematogenic spread means bacteria traveling through blood. Step 2: Urinary tract infections typically occur due to bacteria entering through urethra, not via blood. Step 3: Choice A states bacterial UTIs are usually after haematogenic spread, which is incorrect. Step 4: Therefore, Choice A is NOT true for UTIs. Summary: B, C, and D are incorrect as they align with typical characteristics of UTIs.

Correct Answer: B

Rationale: The correct answer is B: slime mold. Plasmodium is a type of slime mold, specifically a parasitic protist that causes malaria in humans. Slime molds are a group of organisms that share characteristics of both fungi and protozoa. Plasmodium does not belong to the other categories listed: A) protozoan refers to a broad category of single-celled eukaryotic organisms, C) spirochetes are a type of bacteria, and D) helminths are parasitic worms. Therefore, the correct classification for Plasmodium is slime mold.