Mechanism of penicillin killing in the absence of bacterial lysis.

Exposure of group A streptococci (a nonlytic-death phenotype) to benzylpenicillin (penicillin G) produced a dose-dependent, rapid, and extensive hydrolysis of total cellular RNA, with the subsequent loss of hydrolysis products from the cell. This loss of RNA correlated well with loss of viability and was not accompanied by solubilization of the cell wall or comparable losses of either protein or DNA. Simultaneous treatment with penicillin G and either chloramphenicol or rifampin resulted in reduced levels of killing and the complete inhibition of RNA loss. These findings define a new mechanism of penicillin G-induced killing in the absence of cell wall disruption and suggest a basis for drug-induced antagonism of penicillin G-mediated nonlytic death.