microbiology an introduction 12th edition test bank

Correct Answer: B

Rationale: The correct answer is B: Klebsiella pneumoniae. This bacterium is gram-negative, capsulated, and forms lactose-positive colonies. It was first isolated in pneumonia but is more commonly associated with urinary infections, otitis, meningitides, sepsis, and nosocomial infections. Klebsiella pneumoniae fits all the characteristics mentioned in the question, making it the correct choice. Incorrect choices: A: Staphylococcus aureus is gram-positive and does not have a capsule. C: Streptococcus pneumoniae is also gram-positive and does not fit the description given. D: Mycobacterium tuberculosis is an acid-fast bacterium associated with tuberculosis, but it is neither gram-negative nor lactose-positive.

Correct Answer: B

Rationale: The correct answer is B: Isolation on cell cultures. This method is the gold standard for routine mumps diagnosis as it involves isolating the virus in cell cultures to confirm the presence of the mumps virus. PCR (choice A) is used for detecting viral RNA, not for routine diagnosis. ELISA (choice C) detects antibodies, not the virus itself. Immunofluorescence method (choice D) is used for visualizing viral antigens but is not as reliable as isolating the virus in cell cultures for diagnosis.

Correct Answer: B

Rationale: The optochin sensitivity test is used to differentiate Pneumococcal (Streptococcus pneumoniae) from other streptococci. Optochin sensitivity is a characteristic feature of Pneumococcal, as it inhibits its growth. The test involves placing optochin discs on a culture plate and observing the zone of inhibition around the disc for Pneumococcal. Neisseria gonorrhoeae, Staphylococci, and Group A streptococci do not exhibit optochin sensitivity, making them incorrect choices. In summary, the optochin sensitivity test is specific to Pneumococcal, making choice B the correct answer.

Correct Answer: D

Rationale: The correct answer is D because hospital-acquired infections can be caused by a variety of microorganisms, including opportunistic pathogens and obligate pathogens such as bacteria or viruses. Opportunistic microorganisms take advantage of weakened immune systems in hospital patients, while obligate pathogens are capable of causing infections in healthy individuals. Therefore, all the choices are correct in this context as they represent potential etiological causes of hospital-acquired infections.

Correct Answer: A

Rationale: The Ascoli precipitation test is specifically used to detect anthrax agent antigens. The test involves mixing a patient's serum with a solution containing anthrax antigens, leading to precipitation if the antigens are present. Therefore, a positive reaction in this test indicates the presence of anthrax agent antigens. The other choices (B: Brucellosis agent, C: Anaerobic infection toxin, D: Plague agent) are incorrect because the Ascoli precipitation test is not designed to detect these specific agents or toxins.