A patient has been hospitalized with provisional diagnosis of botulism. What serological reaction should be used to reveal botulinum toxin?

Correct Answer: A

Rationale: The correct answer is A: Neutralization reaction. This is the most appropriate serological test to reveal botulinum toxin because it involves mixing the patient's serum with known botulinum antitoxin. If the patient's serum contains botulinum toxin, it will neutralize the antitoxin, leading to a lack of toxin-neutralizing ability. The other choices are incorrect because agglutination reaction involves clumping of cells, not suitable for detecting botulinum toxin; Bordet-Gengou test is used to detect antibodies in pertussis infection, not botulinum toxin; and precipitation reaction involves the formation of a solid when two solutions are mixed, not ideal for detecting botulinum toxin.

Correct Answer: A

Rationale: The correct answer is A: anabolic. Anabolic reactions involve the synthesis of larger organic molecules from smaller precursor molecules. This process requires energy input and is essential for growth and repair in living organisms. Choice B: Catabolic reactions involve the breakdown of larger molecules into smaller ones, releasing energy in the process. This is the opposite of what is described in the question. Choice C: Metabolic is a broad term that encompasses all chemical processes in living organisms, including both anabolic and catabolic reactions. It is not specific to the assembly of small molecules into larger ones. Choice D: "Any of the above" is incorrect because only anabolic reactions specifically involve the assembly of small precursor molecules into larger organic molecules.

Correct Answer: B

Rationale: The correct answer is B: Hepatitis B virus. This is because Hepatitis B virus is a DNA virus, not an RNA virus. The other choices, A (Hepatitis G virus), C (Hepatitis A virus), and D (Hepatitis E virus) are all RNA viruses. Hepatitis B virus is unique as it contains partially double-stranded DNA. DNA viruses replicate through a DNA intermediate, unlike RNA viruses which directly use RNA. Therefore, Hepatitis B virus stands out as the only DNA virus among the given options.

Correct Answer: A

Rationale: The correct answer is A: ocular lens. The ocular lens is the lens closest to the eye in a compound light microscope. This lens is responsible for magnifying the image produced by the objective lens. It typically has a magnification power of 10x. The objective lens, choice B, is positioned closer to the specimen and provides the primary magnification of the image. The condenser, choice C, is located beneath the stage and helps focus light onto the specimen. The stage, choice D, is where the specimen is placed for observation. Therefore, the ocular lens is the correct choice as it is the lens closest to the eye and responsible for further magnifying the image.

Correct Answer: C

Rationale: The correct answer is C: nosocomial infections. Nosocomial infections are infections acquired in healthcare settings. This term specifically refers to infections that occur during the course of receiving medical treatment. The other choices are incorrect because: A: Incidental infections do not necessarily occur in healthcare settings. B: Accidental infections is not a commonly used term in healthcare for infections acquired in healthcare settings. D: Secondary infections refer to infections that occur as a result of a primary infection, not specifically related to healthcare settings.

Correct Answer: A

Rationale: 1. Gram-positive cocci in clusters suggest Staphylococcus species. 2. Catalase-positive and coagulase-positive characteristics match with Staphylococcus aureus. 3. Staphylococcus aureus is a common cause of wound infections due to its virulence factors. 4. Other choices are incorrect: B) S. epidermidis is coagulase-negative and a common contaminant, C) S. pyogenes is catalase-negative, D) Enterococcus faecalis is not typically associated with wound infections.

Correct Answer: C

Rationale: The correct answer is C: Staphylococcus saprophyticus. The rationale is that Staphylococcus saprophyticus is the only one among the listed species that is known to be resistant to novobiocin. This resistance is due to the specific mechanism of action of novobiocin, which targets DNA gyrase, and Staphylococcus saprophyticus possesses an altered DNA gyrase enzyme that renders it resistant to the antibiotic. Staphylococcus aureus and Staphylococcus epidermidis are susceptible to novobiocin, making choices A and B incorrect. Choice D, "none of the listed," is also incorrect as Staphylococcus saprophyticus is indeed resistant to novobiocin.

Correct Answer: B

Rationale: The correct answer is B: Shagreen leather. Yersinia pestis, the bacterium causing plague, forms colonies resembling shagreen leather on a hard nutrient medium due to its distinctive morphology. This morphology includes a rough, irregular, and raised appearance, similar to the texture of shagreen leather. A: Dewdrops - Incorrect. Dewdrops do not accurately describe the colony morphology of Yersinia pestis. C: Lace handkerchief - Incorrect. Lace handkerchief does not accurately describe the colony morphology of Yersinia pestis. D: Mercury drops - Incorrect. Mercury drops do not accurately describe the colony morphology of Yersinia pestis.

Correct Answer: D

Rationale: The correct answer is D: Cytoplasmic membrane - essential. The cytoplasmic membrane is a crucial structure in bacteria as it regulates the passage of substances in and out of the cell, provides structural support, and is essential for maintaining cell integrity. Without a functional cytoplasmic membrane, bacteria would not be able to survive. A: Nucleus is incorrect because bacteria do not have a true nucleus. B: Capsule - non-essential is incorrect because while the capsule provides protection and helps in adherence, it is not essential for bacterial survival. C: Mitochondria is incorrect because bacteria do not have mitochondria; they generate energy through other mechanisms. In summary, the cytoplasmic membrane is essential for bacterial survival, making it the correct choice among the options provided.