Antibacterial Agents 1. Those Affecting Cell Wall Function

The function of any microbial cell wall is a protective one. In Gram-positive bacteria the internal osmotic pressure of the cell is high whereas that in Gram-negative bacteria is much lower, the respective values being about 20 atm and 6 atm. Since the cell wall prevents lysis of the underlying cell membrane against these pressures it is obvious that any agent capable of damaging the cell wall could produce lysis by virtue of the intracellular osmotic pressure. It follows that, as the pressure inside a Gram-negative cell is lower than that of a Gram-positive one, then it would be more difficult to lyse and thus kill the latter type of cell. These generalisations are in the main true since it is more difficult to eradicate an infection caused by Gram-negative cells than Gram-positive. In order to understand the basis of the chemotherapeutic action of antibiotics which affect the structure and function of the cell wall, the nature of the cell wall must be considered.