Integrated Pest Management (IPM) is today a widely accepted strategy for reducing overdependence on chemical insecticides and to reduce their potentially negative environmental and economic effects. Photorhabdus is a gram-negative enteric bacterium that is found in association with entomopathogenic nematodes of the family Heterorhabditidae. The nematodes infect a variety of soil insect pests. Upon entering an insect host, the nematode releases Photorhabdus spp. cells from its intestinal tract, and the bacteria quickly establish a lethal septicemia. When grown in yeast salt broth, in the absence of the nematodes, the bacteria produce a toxin protein that is lethal when fed to the hemolymph of several insect species. Broth cultures of five isolates of Photorhabdus (A, B, C, D, E) were lethal to the nymphs of Galleria mellonella when mixed different concentrations (5,10 and 20 ml) from suspension bacterial cell with two kind of media (wheat bran and fine sand) as compared to broth alone (control). Results obtained showed that, after one day the mortality reached 100 % on sand inoculated with 20 ml cells suspension of the isolates A, C and D. A hyperbolic relationship was observed between different isolates, type of media, doses and time intervals. These bacterial cells were also recovered from the abdominal haemocoele indicating that bacterial symbionts do have a free-living existence and can enter in the haemocoele in the absence of nematode vector.