Rapid identification of Serratia marcescens by coagglutination

All 20 O serotypes of Serratia marcescens produce a common, soluble antigen. Crude antigen was obtained by ammonium sulfate precipitation of spent growth medium, antiserum was produced in rabbits, and a coagglutination test for rapid identification of S. marcescens was developed. A total of 701 clinical isolates of gram-negative bacilli were examined, and a 100% correlation between biochemical identification of S. marcescens and identification by coagglutination was found.