ENTEROCOCCUS-FAECALIS CYTOLYSIN WITHOUT EFFECT ON THE INTESTINAL GROWTH OF SUSCEPTIBLE ENTEROCOCCI IN MICE

A murine model was developed to determine whether the Enterococcus fae calis cytolysin, through its bacteriolytic action on gram-positive bac teria, could promote intestinal overgrowth of cytolytic strains. Sets of E. faecalis strains with varying cytolytic production and susceptib ility to cytolytic activity were mixed 1:1 and allowed to compete in v itro in broth or in vivo after orogastric administration in mice pretr eated with antibiotics. In general, cytolytic strains outgrew, by as m uch as 2000-fold, competing cytolysin-susceptible or -hypersusceptible strains in vitro. In contrast, no growth advantage was observed in vi vo, despite similar transient colonization of the murine intestinal tr act by both cytolytic and cytolysin-susceptible strains. These data su ggest that cytolysin plays little role in promoting intestinal overgro wth of enterococci through bacteriolytic activity.