The β-Lactams Are Narrow Spectrum Antibacterials Because

The β-lactams are narrow spectrum antibacterials because

A) they are analogs for a compound metabolized only by Gram -negative bacteria.
B) they are analogs for a unique cell membrane lipid.
C) they block a synthetic step unique to the Gram-positive bacteria.
D) the outer membrane prevents their entry into cells.
E) the thick peptidoglycan walls prevent their entry into cells.