Nesseriae and Penicillin
Although Nesseriae are gram negative they are sensitive
to penicillin (which is usually used against gram
positive bacteria). Why is this so?
The bacterial cell wall is made primarily of a substance known as
peptidoglycan. It is protein based (peptido-) and sugar based (-glycan).
The sugar parts are actually two sugars called n-acetyl-muramic acid and
n-acetyl-glucosamine. They alternate in long rows. They are joined by
tetrapeptides that hook them together kind of like a chain link fence. This
makes for a very strong cell wall. Penicillin acts by preventing the
tetrapeptides from cross-linking and the cell wall loses its strength. The
organisms then become sensitive to changes in osmotic pressure and burst.
Gram positive organisms have a very thick peptidoglycan layer and therefore
are most sensitive to penicillin based antibiotics. But gram negative
bacteria also have peptidoglycan in their wall, even though it is only about
20%. So penicillin so far has been able to kill gonorrhea organisms.
However, many are becoming resistant to this antibiotic.
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Update: June 2012