ANTIMICROBIAL ACTIVITY OF THREE INSECT SPECIES, CRUDE EXTRACTS AGAINTS CERTAIN MICROBIAL AGENTS.

The aim of the present study was to investigate the antibacterial and antifungal activities of crude extracts of the desert locust, Schistocerca gregaria, the cotton leaf worm, Spodoptera littoralis and the oriental hornet, Vespa orientalis using different solvents; methanol, petroleum ether and chloroform against Gram-positive bacteria; Micrococcus luteus and Staphylococcus aureus, Gram-negative bacteria, Pseudomonas aeruginosa and Escherichia coli and fungi; Penicillium chrysogenum and Candida albicans. Preparation of crude insect extracts from the whole body of the three species were firstly washed with 80 % ethanol as a disinfectant, then rinsed in distilled water, excess water was removed by filter paper, then homogenized in 10 ml of the first solvent, centrifuged at 13,000 r.p.m. for 30 min.at 4ºC, supernatant was removed and used as first solvent extract, residue was soaked in the second solvent then centrifuged, The previous step was carried out with the remain solvent as mentioned before. All solvent extracts were dried by evaporation of solvents for usage in the antimicrobial activity tests. A strong effect against Gram-positive bacteria Micrococcus luteus and Staphylococcus aureus was observed by the extraction of desert locust by petroleum ether as an inhibition zone recorded 30±0.1mm and 32±0.4 mm, respectively. While the inhibition zone effect of the desert locust and the oriental hornet extracted by methanol was 23±0.2mm, 26±0.44mm and 24±0.26mm, 24±0.64mm, respectively. While the oriental hornet extracted by petroleum ether was 26±0.18 mm, 25±0.51mm. On the other hand, Escherichia coli inhibited by the oriental hornet extracts, while Pseudomonas aeruginosa inhibited by two oriental hornet extracted by methanol, petroleum ether and the desert locust extracted by chloroform, respectively. While all extracts except the oriental hornet extracted by chloroform have antifungal activity against Penicillium chrysogenum. Keywords: Antimicrobial activity, Crud extract, Insect, bacteria and fungi.