Answer:
Bacterial cell wall is made of peptidoglycan. A drug which inhibits NAG and NAM linking, inhibits cell wall formation which will lead to death of the bacteria. It will be more effective on gram positive bacteria since the peptidoglycan layer is very thick and there is no outer protection.
In gram negative bacteria the drug needs to cross the outer membrane first to access the cell wall which is not easy. Outer membrane can also evolve its properties to resist the antibiotic like altering its permeability or rendering useless the porins used by drug for transport. Bordetella pertussis is a gram negative bacteria hence is usually resistant to drugs like penicillin which target cell wall synthesis. Hence, the drug would not cause mortality in Bordetella pertussis.
