Correct Answer: D

Rationale: The correct answer is D: Mycoplasma. Mycoplasma is the only bacteria among the choices that have sterols in their cytoplasmic membrane. This feature helps stabilize their membrane structure due to the lack of a cell wall. Legionella (A), Bacillus (B), and Rickettsia (C) do not contain sterols in their cytoplasmic membrane. Legionella has a unique lipid composition, Bacillus has peptidoglycan in its cell wall, and Rickettsia is an intracellular parasite lacking sterols in its membrane.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium appears as purple-stained diplococci with pointed ends on Gram staining. S. pneumoniae is a common cause of pneumonia. It is encapsulated and has a lancet-shaped appearance, which is characteristic of the pointed ends seen in the staining. Staphylococcus aureus (B) typically appears as clusters of gram-positive cocci, not diplococci. Klebsiella pneumoniae (C) is a gram-negative rod, not a diplococci. Neisseria meningitidis (D) is a gram-negative diplococci but typically lacks the pointed ends seen in the staining of S. pneumoniae.

Correct Answer: A

Rationale: The correct answer is A: Epidemic typhus. This disease is caused by the bacterium Rickettsia prowazekii, which is transmitted by body lice. The symptoms include high fever, body rash, and tiny wounds due to scratching. The presence of lice in the clothing suggests a possible lice-borne disease like epidemic typhus. Summary: - B: Tularemia is caused by the bacterium Francisella tularensis, transmitted through ticks, deer flies, and contact with infected animals. Lice are not involved in its transmission. - C: Scabies is a skin infestation caused by the mite Sarcoptes scabiei, leading to itching and skin rashes. It is not associated with high fever or lice infestation. - D: Malaria is caused by Plasmodium parasites, transmitted by infected mosquitoes. The symptoms differ from those described in the scenario, and lice are not involved in its

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the neurotoxin responsible for botulism. Clostridium perfringens causes gas gangrene, not botulism. Escherichia coli and Salmonella enterica are not associated with botulism. Clostridium botulinum is the only bacterium known to produce the toxin causing botulism.

Correct Answer: C

Rationale: The correct answer is C: Epidemic. This term refers to the widespread occurrence of an infectious disease in a specific community or region at a particular time. In this scenario, the infection of many people with a known epidemiological link indicates a localized outbreak within a defined population. Explanation: 1. Epidemic specifically refers to a sudden increase in the number of cases of a disease above what is normally expected in a population. 2. The term "known epidemiological link" suggests a clear connection between the cases, indicating a common source or mode of transmission within a specific group. 3. Endemic (choice A) refers to the constant presence of a disease within a specific geographic area or population. 4. Pandemic (choice B) refers to a global outbreak of a disease that spreads across countries and continents. 5. Sporadic disease (choice D) refers to isolated cases that occur infrequently and without a clear pattern. In summary, an epidemic best describes the situation of many people being