Protection test is a very valuable tool for evaluation of the effectiveness of biological and synthetic immunostimmulators for the honey bee (Apis mellifera L.). Chitosan, extract of Echinacea purpurea, levamisole and clotrimazole protected Escherichia coli D31 non-induced worker bees well against aerosol infection of Pseudomonas aeruginosa isolated from septicaemic bees. The best protective effects were noted for chitosan (Chitosal - Apis Liquid, Vet-Agro Sp.z o.o. Lublin) and for the Extractum Echinacea aqua siccum (Phytopharm) in Escherichia coli D31 induced bees exposed to live cells of Pseudomonas aeruginosa in an aerosol. These two preparation of natural origin, may be used in the honey bee colonies as potent stimulators and modulators of immune response.