Antibiotic tolerance among clinical isolates of bacteria
One of the unique features of p-lactam antibiotics and other cell-wall inhibitors like vancomycin and bacitracin is that they can rapidly kill and in many cases lyse susceptible bacteria. Many other types of antibacterial agents (e.g., trimethoprim or chloramphenicol) are primarily bacteriostatic: they inhibit multiplication but do not cause an irreversible inactivation of the cell. In 1970 the characterization of a novel type of pneumococcal mutant was reported in the literature [1]. This mutant grows in normal generation times and is as sensitive to growth inhibition by penicillin as the wild-type parent strain. However, while cultures of the parent