Identification of mosquito larvicidal bacterial strains isolated from north Sinai in Egypt

Mosquito borne diseases constitute a serious health hazard to human. It has been established that, mosquito's females as blood sucking insects, are vectors of a multitude disease of man and animals in different countries through transmission of pathogenic agents. Mosquitoes are belonging to the order Diptera and family Culicidae which include the genera of medical importance, Aedes, Anopheles, Culex and Mansonia. At least 90% of the world malaria (Anopheles), yellow fever (Aedes), dengue (Aedes), encephalitides (Aedes) and lymphatic filariasis (Aedes, Anopheles and Culex) occurs in the tropics where the environmental conditions favor insect vectors responsible for the transmission of diseases Rawlins, 1989.Controlling insect populations with chemical insecticides has proven useful. Over time, mosquitoes developed resistance to chemical insecticides, toxicity to non target organisms, increased public awareness of the toxicity hazards, undermined this control strategy's efficacy. Within this scenario, biological control based on insecticidal bacteria has proven effective in controlling insect vectors. Mosquitocidal Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus are used as an alternative for synthetic chemical insecticide in controlling larvae of mosquitoes over two decades. B. thuringiensis subsp. israelensis has a wider spectrum of activities against Anopheles, Culex and Aedes spp; while the target spectrum of B. sphaericus is restricted mainly to Culex, for a lesser extent to Anopheles and only few Aedes species. Compared to B. thuringiensis subsp. israelensis, the popular microbial mosquito control agent, B. sphaericus has major advantage. It appears to persist in the environment longer especially in polluted water, and thus can establish a longer lasting control of larval populations.The toxicity of B. sphaericus strains is mainly attributed to the presence of binary toxin (Bin A, Bin B) and/or mosquitocidal (Mtx) toxin genes. Binary toxin is c