Microscopic examination of pus from a wound revealed Gram-positive cocci in grape-like clusters. The bacteria were catalase- and coagulase-positive. Identify the microorganism.

Correct Answer: A

Rationale: Step 1: Gram-positive cocci in grape-like clusters suggest Staphylococcus. Step 2: Catalase-positive indicates Staphylococcus (negative for Streptococcus). Step 3: Coagulase-positive is specific for Staphylococcus aureus. Summary: B: Streptococcus pyogenes is catalase-negative. C: Enterococcus faecalis does not form grape-like clusters. D: Micrococcus luteus is catalase-positive but not coagulase-positive.

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: C

Rationale: The correct answer is C: after repeated exposure for days. Subacute toxic effects typically manifest after a period of time that is longer than immediate (A) or acute (B) effects but shorter than chronic effects (D). This duration of days aligns with the definition of subacute, which refers to effects that occur gradually over a relatively short time frame. It is important to differentiate between the timing of toxic effects to accurately assess the potential harm caused by a substance. Choices A, B, and D are incorrect because they do not align with the characteristic time frame associated with subacute toxic effects.

Correct Answer: A

Rationale: The correct answer is A: Halophiles. Halophiles are bacteria that thrive in high-salinity environments due to their ability to tolerate high salt concentrations. They have adapted mechanisms to maintain osmotic balance and survive in such extreme conditions. Thermophiles (B) thrive in high-temperature environments, not high-salinity. Acidophiles (C) prefer acidic conditions, not high-salinity. Mesophiles (D) grow optimally at moderate temperatures and are not specifically adapted to high-salinity environments.

Correct Answer: A

Rationale: The correct answer is A because the cloudy surface indicates that the bacteria are growing where oxygen is present (aerobes), causing turbidity. The clear bottom suggests that the bacteria are not growing in the absence of oxygen. Choices B, C, and D are incorrect because the observed phenomena do not necessarily indicate the need for an anaerobic chamber, enzyme deficiencies, or the microorganism being non-aerotolerant.

Correct Answer: B

Rationale: The correct answer is B: cytopathic effect. When viruses infect cell cultures, they induce degenerative changes known as cytopathic effects, which include cell shrinkage, rounding, detachment, and cell death. This term specifically refers to the damage caused by viral replication within the cells. A: Cytolytic effect refers to the destruction of cells by viruses, which is a more specific type of cytopathic effect involving cell lysis. C: Cytotoxic effect typically refers to the toxic effects of substances on cells, not specifically related to viral propagation. D: The statement that all three answers are correct is incorrect as only option B accurately describes the degenerative changes resulting from viral propagation in infected cell cultures.

Correct Answer: B

Rationale: The correct answer is B: Zoonosis. Tularemia is primarily a zoonotic disease, meaning it is transmitted from animals to humans. The bacterium that causes tularemia, Francisella tularensis, commonly infects animals like rabbits, rodents, and ticks, which serve as reservoir hosts. Humans can get infected through direct contact with infected animals, insect bites, or contaminated water or soil. This zoonotic nature of tularemia distinguishes it from anthroponosis (A), which is transmitted only between humans, and sapronosis (C), which is transmitted through non-living environmental sources. Choice D is incorrect because there is a correct answer, which is zoonosis.

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.

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.