Abstract
The isolate (Enterobacter sp.) from the infected larvae was analysed. By the percoll density gradient method, bacterial cells obtained as a white opaque band in the center of the centrifugation tube were collected. The purified bacteria were injected into rabbits as an antigen to prepare an antiserum. The antiserum reacted only with the bacterial cells of this particular isolate when the electrosyneresis and fluorescent antibody method were applied. No reaction was observed with other bacteria used as controls. A serum separately prepared against Serratia marcescens was found to react only with Serratia marcescens, without showing any reaction with the cells from Enterobacter sp. Subsequent observation by the electrosyneresis method revealed that the inoculation of the bacterial cells into larvae led to the detection of the specific antigen only in the infected larvae. Therefore it was possible to determine by the serological reaction whether the infection had taken place. The multiplication of the bacteria in the cytoplasm of the midgut was also observed with the fluorescent antibody method. Specific fluorescence was observed only in the cytoplasm of the cylindrical cells in the midgut. This reaction was intensified with the multiplication of the bacteria. The growth phase observed with an optical-microscope was identical with that observed with an electron-microscope.
