Antibiotics and Bacteria Types
Country: United States
Date: July 2008
For a given antibiotic is there a difference in
susceptibility between the gram+ and the Gram- bacteria?
The difference between Gram+ and Gram- is in the cell walls of the
bacteria, so for example Penicillin, which inhibits the synthesis of
Gram- cell walls, does not work against Gram+ bacteria.
Ron Baker, Ph.D.
It depends on the antibiotic but yes. Even if two bacteria are susceptible
to the same antibiotic, they may not be AS sensitive. Many antibiotics work
by breaking down components in the cell wall called peptidoglycans (PG).
They act like a chain link fence to hold the cell wall together. It's like
taking a wire cutter and clipping the fence. Gram positives have a much
thicker layer of PG than gram negatives even though both have them. So is
you are talking about one of these there is probably a difference. Other
antibiotics work by other means and it may not make a difference if they are
g+ or g-.
Click here to return to the Molecular Biology Archives
Update: June 2012