microbiology chapter 13 test bank

Correct Answer: B

Rationale: The correct answer is B: For HIV. Pneumocystis pneumonia in a young man with CD4+ cells less than 200/mm3 is highly suggestive of HIV infection. HIV weakens the immune system, leading to opportunistic infections like pneumocystis pneumonia. Testing for HIV is crucial for diagnosis and appropriate management. Explanation for other choices: A: Testing for ureaplasma urealyticum is not indicated in this case as the symptoms and CD4+ cell count point towards an HIV-related infection. C: Testing for Treponema pallidum (syphilis) is not relevant in the context of a young man with pneumocystis pneumonia and low CD4+ cell count. D: Testing for Neisseria gonorrhoea is not appropriate in this scenario as the symptoms and CD4+ cell count suggest an underlying HIV infection rather than a bacterial sexually transmitted infection.

Correct Answer: A

Rationale: The correct answer is A: Cell wall. Mycoplasma species lack a cell wall, making them unique among bacteria. This is because they have a flexible cell membrane that provides structural support instead of a rigid cell wall. The absence of a cell wall allows them to be pleomorphic and gives them resistance to certain antibiotics targeting cell wall synthesis. Plasma membrane (B), DNA (C), and ribosomes (D) are present in Mycoplasma species, so they are not the correct answer.

Correct Answer: B

Rationale: The correct answer is B: BCG. Bacille Calmette-Gu�rin (BCG) vaccine is used for the prevention of tuberculosis. BCG is a live attenuated strain of Mycobacterium bovis that helps the immune system recognize and fight off tuberculosis bacteria. Specific anti-tuberculosis serum (A) is not used for prevention but for treatment. DTP (C) stands for diphtheria, tetanus, and pertussis vaccine, not specific for tuberculosis prevention. PPD (D) is a tuberculin skin test used for diagnosis, not prevention. Thus, BCG is the correct choice for tuberculosis prevention.

Correct Answer: A

Rationale: Step-by-step rationale: 1. IgG is the most abundant immunoglobin in a normal healthy adult due to its long half-life and diverse functions. 2. It plays a crucial role in immune response by neutralizing pathogens and enhancing phagocytosis. 3. IgA is mainly found in mucosal areas, IgE is involved in allergic reactions, and IgD's function is not fully understood. 4. Therefore, IgG is the correct answer as it is the predominant immunoglobin in circulation, providing broad immune protection.

Correct Answer: C

Rationale: The correct answer is C because Rickettsia requires living cells for growth and replication. Chick embryos, cell cultures, and lab animals provide a suitable environment for Rickettsia isolation. Skin-allergy tests (A) and serological methods for proving antibodies (B) are not directly used for isolating Rickettsia as they do not support the growth of the bacteria. "None of the above" (D) is incorrect as option C involves the appropriate methods for isolating Rickettsia.