Polymyxin B is a cationic surface agent that binds to the LPS of the cell, which
ID: 300805 • Letter: P
Question
Polymyxin B is a cationic surface agent that binds to the LPS of the cell, which results in increased permeability and cell death. Gram-positive bacteria are more resistant to polymyxin B than Gram-negative bacteria for all of the following reasons EXCEPT: O Gram-positive bacteria possess a cell wall and Gram-negative bacteria do not Gram-positive bacteria possess a thick peptidoglycan layer, which makes it difficult for the drug to reach the plasma membrane. O Polymyxin B disrupts the outer membrane in Gram-negative bacteria. All of the above explain why Gram-positive bacteria are more resistant to polymyxin B.Explanation / Answer
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Gram-Positive Bacteria has a cell wall composed of a thick layer of peptidologlycan containing teichoic and lipoteichoic acid complexed to the peptidoglycan.Gram-positive bacteria are typically more resistant because they have thick cell wall that protects them from cell lysis.
Polymyxin B disrupts plasma membranes
Polymyxins bind to and disrupt the negatively charged lipopolysaccharide (LPS) of the outer membrane of Gram-negative bacteria, allowing the passage of the polymyxin into the periplasmic space.