Which of the following are most susceptible to complement lysis?

• A. Gram-positive bacteria.
• B. Gram-negative bacteria.
• C. Bacteriophages.
• D. Prions.

Answer: (B)

Verified step by step guidance

1. Understand the role of the complement system: The complement system is a part of the immune system that enhances the ability to clear microbes and damaged cells. It promotes inflammation and attacks the pathogen's cell membrane.
2. Identify the structure of Gram-positive and Gram-negative bacteria: Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides.
3. Consider the mechanism of complement lysis: The complement system can form a membrane attack complex (MAC) that creates pores in the cell membrane, leading to cell lysis.
4. Analyze the susceptibility of different organisms: Gram-negative bacteria are more susceptible to complement lysis because the MAC can more easily penetrate their outer membrane compared to the thick peptidoglycan layer of Gram-positive bacteria.
5. Evaluate the other options: Bacteriophages and prions are not cellular organisms and do not have membranes that can be targeted by the complement system, making them less susceptible to complement lysis.