microbiology chapter 12 test bank

Correct Answer: B

Rationale: The correct answer is B: Measles. Immunosuppressive drugs are not used for treating viral infections like measles as they target the immune system and can worsen the infection. Organ transplantation requires immunosuppressive drugs to prevent organ rejection. Autoimmune diseases involve an overactive immune response, so immunosuppressive drugs are used to reduce this response. Hemolytic disease of the newborn can be treated with immunosuppressive drugs to prevent the destruction of red blood cells.

Correct Answer: A

Rationale: Step 1: Mycobacterium leprae is the bacterium responsible for causing leprosy, a chronic infectious disease affecting the skin and nerves. Step 2: Neisseria gonorrhoeae causes gonorrhea, a sexually transmitted infection. Step 3: Streptococcus pneumoniae causes pneumonia and other respiratory infections. Step 4: Clostridium perfringens causes gas gangrene and food poisoning. Summary: A is correct as Mycobacterium leprae specifically causes leprosy, while B, C, and D cause different diseases unrelated to leprosy.

Correct Answer: B

Rationale: The correct answer is B: mutualism. In mutualism, both organisms benefit from the relationship. This is because they provide each other with resources or services that help both parties. In contrast, commensalism (A) is a relationship where one organism benefits while the other is neither helped nor harmed. Parasitism (C) is a relationship where one organism benefits at the expense of the other. Competition (D) is a relationship where both organisms are negatively affected as they compete for limited resources. Therefore, mutualism is the correct answer as it describes a mutually beneficial relationship between two organisms.

Correct Answer: C

Rationale: Step 1: S. aureus is known to produce hemolysins, leucocidins, and enterotoxin. Step 2: S. aureus colonies usually exhibit golden-yellow pigmentation with beta-hemolytic zones. Step 3: S. aureus has developed resistance to penicillin due to the production of beta-lactamase. Step 4: Therefore, statement C is not true as S. aureus is not always sensitive to penicillin. Summary: Choices A and B are correct statements about S. aureus, while choice C is incorrect due to the increasing penicillin resistance seen in S. aureus.

Correct Answer: D

Rationale: The correct answer is D: Immunocomplex. In this case, the patient's symptoms of fever, joint pains, rash, and itch along with leukopenia and thrombocytopenia indicate a serum sickness reaction. This is a type III hypersensitivity reaction where antigen-antibody complexes deposit in tissues, leading to inflammation and tissue damage. The symptoms typically occur 1-2 weeks after exposure to the antigen. Anaphylactic reaction (choice A) is immediate and involves IgE antibodies. Cytotoxic reaction (choice B) involves destruction of cells by antibodies. Delayed hypersensitivity (choice C) usually takes 48-72 hours to develop and involves T-cells. Therefore, the correct answer is D as it aligns with the symptoms and timeline of a type III hypersensitivity reaction.