Microbiology An Introduction Tortora Test Bank

Correct Answer: B

Rationale: The correct answer is B: Availability of cell-mediated immunity to tuberculosis. A negative Mantoux test indicates the presence of an immune response to the TB bacteria, as the test measures the body's delayed hypersensitivity reaction to TB antigens. This means the child has been exposed to TB in the past or has been vaccinated, resulting in the development of cell-mediated immunity against TB. Incorrect choices: A: No cell-mediated immunity to tuberculosis - This is incorrect as a negative Mantoux test actually indicates the presence of cell-mediated immunity. C: No antibodies to the tuberculosis bacteria - Mantoux test measures cell-mediated immunity, not antibody response. D: No anti-toxic immunity to tuberculosis - Mantoux test does not assess anti-toxic immunity, it specifically measures cell-mediated immunity.

Correct Answer: B

Rationale: Rationale: 1. The grain-like sediment indicates a precipitation reaction. 2. Precipitins are antibodies that cause precipitation reactions. 3. In serological diagnostics, precipitation reactions are used to detect specific antibodies. 4. Therefore, the reaction revealed in this scenario is due to the presence of precipitins. Summary: A: Bacteriolysins - These antibodies cause bacterial lysis, not precipitation. C: Antitoxins - These antibodies neutralize toxins, not involved in precipitation reactions. D: Opsonins - These antibodies enhance phagocytosis, not related to precipitation reactions.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive diplococci with a capsule is characteristic of S. pneumoniae. This bacterium is a common cause of pneumonia, especially in patients with fever and cough. It is also known for causing infections such as otitis media and sinusitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form diplococci or have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus commonly associated with meningitis, not pneumonia. Klebsiella pneumoniae (D) is a Gram-negative rod, not a diplococcus, and is more commonly associated with pneumonia in immunocompromised patients.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known to produce a blue-green pigment called pyocyanin, which is characteristic of the organism. Additionally, it has a distinct fruity odor due to the production of certain volatile compounds. Escherichia coli (B) does not produce blue-green pigment or have a fruity odor. Klebsiella pneumoniae (C) and Proteus mirabilis (D) also do not exhibit these specific characteristics associated with Pseudomonas aeruginosa.

Correct Answer: A

Rationale: The correct answer is A: BK virus. BK virus is a common cause of hemorrhagic cystitis, especially in immunocompromised individuals. It infects the urinary tract, leading to inflammation and bleeding in the bladder. Enteroviruses, Flaviviruses, and Coronaviruses do not typically cause hemorrhagic cystitis. Enteroviruses usually cause respiratory and gastrointestinal infections, Flaviviruses are commonly associated with diseases like dengue fever and Zika virus, and Coronaviruses are known for causing respiratory illnesses such as COVID-19. Hence, the correct answer is A as it is the only virus among the options known to cause hemorrhagic cystitis.