microbiology basic and clinical principles test bank

Correct Answer: B

Rationale: The capsule of Bacillus anthracis is made of polypeptide. This is because the capsule is composed of a protein-based material that surrounds the bacterium, providing protection and aiding in its virulence. Polysaccharides, lipids, and the absence of capsules are not characteristic of Bacillus anthracis' capsule structure, making choices A, C, and D incorrect, respectively.

Correct Answer: D

Rationale: The correct answer is D: Propionibacterium acnes. This bacterium is not a fungus, but a common skin bacteria. Fungal vaginitis is typically caused by Candida albicans or other fungal species, not by bacteria like Escherichia coli, Streptococcus agalactiae, or Klebsiella oxytoca. Propionibacterium acnes is not associated with vaginal infections, making it the correct answer in this context.

Correct Answer: A

Rationale: The correct answer is A: ED50. The time response does not measure the ED50 because ED50 refers to the effective dose needed to produce a response in 50% of the population, which is a dose-related concept, not a time-related one. Peak effect time, onset of response, and threshold level are all time-related measures in pharmacology. Peak effect time is the time taken to reach the maximum response, onset of response is the time taken for the response to start, and threshold level is the minimum dose or concentration required to produce a response. Therefore, A is the correct answer as it is the only choice that is not a time-related measure in this context.

Correct Answer: D

Rationale: Rationale: After a splenectomy, patients are at high risk of infections caused by encapsulated bacteria such as Streptococcus pneumoniae, Listeria monocytogenes, and Salmonella. The spleen plays a crucial role in the immune response against encapsulated bacteria, and its absence increases susceptibility to these specific pathogens. Therefore, all choices are correct as patients are at risk of infections from all three types of bacteria mentioned.

Correct Answer: B

Rationale: The correct answer is B: Precipitins. When a granular sediment forms at the bottom of the test-tubes, it indicates the formation of antigen-antibody complexes that are insoluble and precipitate out of the solution. Precipitins are antibodies that specifically react with antigens to form insoluble complexes. Agglutinins cause clumping of cells, opsonins enhance phagocytosis, and bacteriolysins lyse bacteria. These processes do not result in the formation of a granular sediment, making them incorrect choices in this context.