38th Annual Meeting of the Society for Invertebrate Pathology

Enterobacteriaceae of the genus Xenorhabdus and Photorhabdus are potent pathogens of a large spectrum of insect species (Boemare N., 2002, in "Entomopathogenic nematology", Gaugler R ed., CABI pub., pp. 35-56) some strains of which are emerging pathogen for human (Gerrard J. et al., 2004, Microbes and Infection, 6, 229-237). Insect larvae die in a few days after infection. Because Xenorhabdus and Photorhabdus septicemia arises in the insect body, it is obvious that these bacteria are able to escape defense reactions and especially the cellular ones that are early settled after the pathogen penetration. Whereas inhibitors of the PO system (Brehélin M. et al., 1989, Insect Biochemistry, 19, 301-307) and of eicosanoids (Park Y. and Kim Y., 2000, Journal of Insect Physiology, 46, 1469-1476) are secreted by these entomopathogenic bacteria, the means by which they escape the defense reactions are very poorly understood. In this review we show that different toxins are secreted by these bacteria and have the insect immunocytes (haemocytes) as main targets. There is a high redundancy in the kinds of secreted immunodepressive toxins and in their modes of action.