How do Gram-negative bacteria typically respond to exposure to antibiotics?

How do Gram-negative bacteria typically respond to exposure to antibiotics?

• A. They easily absorb antibiotics and become resistant
• B. They develop a thick peptidoglycan layer to fend off antibiotics
• C. They use their outer membrane as a barrier to reduce antibiotic efficacy
• D. They actively pump antibiotics out of the cell

Answer: (C)

Gram-negative bacteria possess an outer membrane that serves as a significant barrier to many antibiotics. This unique structural feature is composed of a lipid bilayer and is strategically located outside the thin peptidoglycan layer. The outer membrane contains porins, which are proteins that can selectively allow certain molecules to pass through, but many antibiotics are too large or too polar to penetrate this barrier effectively. As a defense mechanism, Gram-negative bacteria can utilize this outer membrane to limit the access of antibiotics, thereby reducing their efficacy. This is particularly relevant because it means that even if an antibiotic is present in the environment, it may not reach its target within the bacterial cell, making it less effective in combating infection. In contrast to this mechanism, Gram-positive bacteria, which lack this outer membrane, have a thicker peptidoglycan layer, making them sensitive to different types of antibacterial agents. However, this characteristic is not applicable to Gram-negative bacteria, as their resistance primarily relies on the outer membrane's barrier function and not merely on the thickness of their peptidoglycan. Additionally, while Gram-negative bacteria can indeed develop active efflux pumps that expel antibiotics, which is a common resistance mechanism, the question specifically addresses the typical initial response related to structural barriers

Gram-negative bacteria possess an outer membrane that serves as a significant barrier to many antibiotics. This unique structural feature is composed of a lipid bilayer and is strategically located outside the thin peptidoglycan layer. The outer membrane contains porins, which are proteins that can selectively allow certain molecules to pass through, but many antibiotics are too large or too polar to penetrate this barrier effectively.

As a defense mechanism, Gram-negative bacteria can utilize this outer membrane to limit the access of antibiotics, thereby reducing their efficacy. This is particularly relevant because it means that even if an antibiotic is present in the environment, it may not reach its target within the bacterial cell, making it less effective in combating infection.

In contrast to this mechanism, Gram-positive bacteria, which lack this outer membrane, have a thicker peptidoglycan layer, making them sensitive to different types of antibacterial agents. However, this characteristic is not applicable to Gram-negative bacteria, as their resistance primarily relies on the outer membrane's barrier function and not merely on the thickness of their peptidoglycan.

Additionally, while Gram-negative bacteria can indeed develop active efflux pumps that expel antibiotics, which is a common resistance mechanism, the question specifically addresses the typical initial response related to structural barriers