GENERATION AND TESTING OF MUTANTS OF ENTEROCOCCUS-FAECALIS IN A MOUSEPERITONITIS MODEL

A previously described mouse peritonitis model was used to study deriv atives of Enterococcus faecalis strain OGIRF The addition of sterile r at fecal extracts (SRFE) lowered the LD50 of OGIRF >10-fold. Hemolysin production caused a 35-fold lower LD50 and a much shorter survival, s imilar to previous results using a peritonitis model without SRFE, A p urine (but not a pyrimidine) auxotroph was considerably less lethal th an wild type; gelatinase mutants were also attenuated. A suicide vecto r was generated with an enterococcal selectable marker in order to dis rupt a gene encoding an E. faecalis antigen; the resulting mutant was not attenuated despite a slower growth rate. In conclusion, this model allows attenuated mutants to be detected, corroborates prior reports that hemolysin is a virulence factor, and suggests a role for gelatina se in virulence of E. faecalis in mice; the attenuated purine auxotrop h may provide a system for developing vectors for in vivo expression s ystems.