microbiology an evolving science test bank

Correct Answer: D

Rationale: The correct answer is D because all three bacteria (Salmonella enterica, Escherichia coli, Pseudomonas aeruginosa) are known to produce endotoxins, specifically lipopolysaccharides in their cell walls. Endotoxins are released upon bacterial cell death and can trigger an immune response, leading to septic shock. Salmonella and E. coli are common causes of bacterial infections, while Pseudomonas is associated with nosocomial infections. Therefore, all of the above choices are correct in terms of producing endotoxins that can cause septic shock. Choices A, B, and C are incorrect individually because they do not encompass all the bacteria known to produce endotoxins that can lead to septic shock.

Correct Answer: A

Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacterium is known for causing tuberculosis, as it specifically infects the lungs and can lead to serious respiratory issues. Mycobacterium leprae (Choice B) causes leprosy, not tuberculosis. Escherichia coli (Choice C) is a common bacteria found in the intestines and is not associated with tuberculosis. Streptococcus pneumoniae (Choice D) causes pneumonia, but not tuberculosis. Therefore, the correct choice is A because Mycobacterium tuberculosis is the specific bacterium responsible for causing tuberculosis.

Correct Answer: A

Rationale: The correct answer is A because it specifies the commonly used parameters for autoclaving sterilization: 1.0 atm pressure, 120� C temperature, and 15-20 minutes duration. This combination ensures effective sterilization by providing the necessary heat and pressure for killing microorganisms. Rationale: 1. Pressure of 1.0 atm: Standard atmospheric pressure commonly used in autoclaving. 2. Temperature of 120� C: Optimal temperature for sterilization without causing damage to heat-sensitive materials. 3. Duration of 15-20 minutes: Time required for heat and pressure to penetrate and kill microorganisms effectively. Summary of Incorrect Choices: B: Incorrect temperature and duration, too high and long, may damage materials. C: Incorrect pressure and temperature, higher pressure and temperature not commonly used. D: Incorrect temperature, too high, can damage materials, and duration is longer than necessary.

Correct Answer: A

Rationale: Step 1: Endo agar is a selective and differential media commonly used to isolate gram-negative bacteria. Step 2: Colorless colonies on Endo agar indicate the absence of lactose fermentation. Step 3: Salmonella is a gram-negative bacterium that does not ferment lactose, leading to colorless colonies on Endo agar. Step 4: Therefore, the correct answer is A: Salmonella. Summary: B: Escherichia coli ferments lactose, producing pink colonies on Endo agar. C: Staphylococcus is a gram-positive bacterium and would not grow on Endo agar. D: Shigella is a gram-negative bacterium but ferments lactose, resulting in pink colonies on Endo agar.

Correct Answer: B

Rationale: The correct answer is B: Humoral immunity. Humoral immunity involves the production of antibodies by B cells that can bind to antigens on viruses, leading to their agglutination. This process prevents the spread of the virus in the body. Passive immunity (A) involves receiving pre-formed antibodies, not the production of antibodies. Cell-mediated immunity (C) involves the activation of T cells, not the direct agglutination of viruses. Non-specific immunity (D) refers to general defense mechanisms like inflammation and fever, not targeted agglutination of viruses.