Question

Biologic agents differ from other injurious agents in that they are able to replicate and can continue to produce their injurious effects. How do Gram-negative bacteria cause harm to the cell?

Answer 1

The question is incomplete as it does not have the options which are:

A. Gram-negative bacilli cannot cause harm to the cell; only Gram-positive bacilli can harm the cell.

B. Gram-negative bacilli release endotoxins that cause cell injury and increased capillary permeability.

C. Gram-negative bacilli excrete elaborate exotoxins that interfere with cellular production of ATP.

D. Gram-negative bacilli enter the cell and disrupt its ability to replicate.

Answer:

B. Gram-negative bacilli release endotoxins that cause cell injury and increased capillary permeability.

Explanation:

Gram-negative bacteria are pathogenic in nature due to the composition of their cell wall. Their cell wall contains an additional layer of a molecule called lipopolysaccharides or LPS.

The LPS layer is toxic in nature and is known as endotoxin and is involved in the pathogenicity of the bacteria as the toxin causes the injury to the Endothelial cell membrane of the host cell.  

When the bacteria cell is lysed and the LPS circulates in the blood, then LPS binds the receptors and acts on CD14. This attracts the neutrophils at the site and can cause vascular injury due to increased capillary permeability.

Thus, Option-B is the correct answer.