A sick man with high temperature and a lot of tiny wounds on the body has been admitted to the hospital. Lice have been found in the folds of his clothing. What disease can be suspected in the patient?

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: C

Rationale: Correct Answer: C - Immunological tolerance to the pathogen Rationale: 1. Immunological tolerance is when the immune system does not mount a response against specific antigens to prevent autoimmunity. 2. In the context of infection, tolerance to the pathogen means the immune system does not recognize the pathogen as a threat and does not initiate a protective response. 3. This lack of response leaves the host vulnerable to infection as there is no specific immune defense mechanism activated against the pathogen. Summary of incorrect choices: A: Opsonic action of antibody - enhances phagocytosis of pathogens B: Viral neutralization by specific antibody - prevents viral entry into host cells D: Neutralization of protein exotoxin - prevents the harmful effects of toxins produced by pathogens.

Correct Answer: A

Rationale: The correct answer is A: protein envelope around the nucleic acid. Viral capsid is the protein coat that surrounds and protects the viral nucleic acid (DNA or RNA). This structure helps in protecting the genetic material from degradation and facilitates the attachment of the virus to host cells. Option B is incorrect as it suggests the nucleic acid is coated with protein, which is not the case. Option C is incorrect as not all viruses have an outer membrane. Option D is incorrect as viruses typically do not have a lipoprotein membrane.

Correct Answer: A

Rationale: The correct answer is A: infants. Staphylococcal scalded skin syndrome is most common in infants because their immune systems are not fully developed, making them more susceptible to Staphylococcus aureus infections. This bacteria produces exotoxins that cause the skin to blister and peel, characteristic of the syndrome. Adolescents, young adults, and the elderly have more mature immune systems, making them less vulnerable to this specific infection. Therefore, infants are at a higher risk for developing Staphylococcal scalded skin syndrome compared to other age groups.

Correct Answer: D

Rationale: The correct answer is D: Mesosomes. Mesosomes are infoldings of the prokaryotic cytoplasmic membrane that play a role in cell division and respiration. This structure is not found in eukaryotic cells. Cristae (A) are infoldings of the mitochondrial inner membrane in eukaryotic cells. Granum (B) refers to stacks of thylakoid membranes in chloroplasts. Flagella (C) are whip-like structures used for movement and are not related to cytoplasmic membrane invaginations. Therefore, the correct answer is D as mesosomes are unique to prokaryotic cells and are involved in various cellular processes.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci arranged in clusters, catalase-positive, and coagulase-negative characteristics are indicative of Staphylococcus species. Staphylococcus epidermidis is a common skin commensal that causes wound infections. Staphylococcus aureus is coagulase-positive and often causes more aggressive infections. Streptococcus pyogenes is catalase-negative and typically forms chains, not clusters. Enterococcus faecalis is catalase-negative and commonly found in the GI tract, not a common cause of wound infections.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria - Salmonella enterica, Clostridium botulinum, and Escherichia coli - are commonly associated with foodborne illnesses. Salmonella causes gastroenteritis, Clostridium botulinum causes botulism, and E. coli can lead to severe food poisoning. Each bacterium has different mechanisms of causing illness, but all can be transmitted through contaminated food. Choices A, B, and C alone are incorrect because they do not encompass the full spectrum of bacteria commonly linked to foodborne illnesses.

Correct Answer: A

Rationale: The correct answer is A: Cell wall. In the Gram staining method, the primary differentiation of bacteria is based on the composition of their cell walls. Gram-positive bacteria have a thick layer of peptidoglycan in their cell walls, which retains the crystal violet dye and appears purple under the microscope. On the other hand, Gram-negative bacteria have a thinner layer of peptidoglycan and an outer membrane, which allows the crystal violet dye to be washed out during the decolorization step and take up the counterstain safranin, appearing pink. The different responses to stains are primarily due to the structural differences in the cell walls of these two types of bacteria. Summary: - Choice A: Cell wall is correct because it determines the differential staining in Gram staining. - Choice B: Cytoplasm is incorrect as it does not directly influence the staining properties of bacteria. - Choice C: Cytoplasmic membrane is incorrect as it is not the main structural

Correct Answer: B

Rationale: The correct answer is B (Urethra). Resident microflora are typically found in various parts of the body where they establish a stable population without causing harm. The urethra is one of the locations where resident microflora are commonly present, helping to maintain a healthy microbial balance and prevent pathogenic bacteria from colonizing the area. In contrast, choices A, C, and D are not typical locations for resident microflora. Blood is normally sterile, the lungs have a different microbial environment due to their exposure to the external environment, and the cerebro-spinal fluid is also typically sterile to prevent infections in the central nervous system.