The use of insects in folk medicine is widespread. This study was carried out in order to investigate the in vitro antimicrobial activity of the Acanthoplus discoidalis insect extract. Insects were harvested from maize fields by hand picking and prepared to produce the extract. In the disc-diffusion assay, plate count agar plates were inoculated with 100μl of each of the test microorganism adjusted with peptone to standardised inoculums of 5 log CFU/ml in triplicate and spread with sterile glass rods. Filter paper discs 8mm diameter dipped in extract were placed on the agar plates. The insect extract and the control gentamycin were tested against ten test bacteria namely Lactobacillus sp., Staphylococcus aureus, Salmonella enteritidis, Shigella sp., Salmonella typhimurium, Pseudomonas aeruginosa, Proteus vulgaris, Bacillus subtilis, F. streptococcus and Escherichia coli. The insect extract was able to inhibit growth of both gram negative Shigella sp., P. aeruginosa, P. vulgaris, E. coli and gram positive B. subtilis, Lactobacillus sp. bacteria and Group F. streptococcus. P. aeruginosa had the highest zone of inhibition of 17 mm followed by Lactobacillus sp. bacteria 16 mm. No activity was observed against S. aureus, S. enteritidis and S. typhimurium.

Keywords: Acathoplus discoidalis, folk medicine, antimicrobial activity.