How Resistance is Acquired 1. Spontaneous Mutations - Most bacteria acquire antibiotic resistance by spontaneous mutations in their genetic material. If a mutant happens to be resistant to a drug, that mutant and its progeny will survive, whereas the nonresistant cells will die. After a few generations, most of the survivors will be resistant to the drug. L forms - Some species of bacteria can lose their cell wall and swell into irregularly shaped cells called L forms .
L forms can arise spontaneously and can persist and divide repeatedly.
They can spontaneously revert to normal-walled cells. Penicillin contains a structure called a beta lactam ring . Some bacteria have an enzyme called beta lactamase that will break the beta lactam ring in penicillins. Bacteria that have this enzyme are also resistant to some cephalosporins that also contain beta lactam rings. E. Limiting Drug Resistance 1.