A Critical Assessment of Bombyx mori Haemolymph Extract on Staphylococcus aureus an In vitro and In silico Approach

The newly reemerging drug-resistant Gram-positive pathogens require the discovery of new drug targets and the development of new therapeutics. We focus on antimicrobial proteins which inhibits growth of Staphylococcus aureus. In the present study fifth instar Bombyx mori larvae was used and infected with S. aureus by intrahaemocoelic injection of bacterial sample. The haemolymph was collected from the healthy and infected larvae after 24 h of infection and stored at -4°C in eppendorf tubes until use. Haemolymph extract was prepared and antimicrobial activity was done by the classical well diffusion method. Haemolymph extract prepared form infected larvae exhibit maximum zone of inhibition on S. aureus when compared with healthy haemolymph extract. Bioinformatics tools were used to find out the molecular interaction and binding mode of antimicrobial peptides from B. mori such as Moricin and Cecropin on three different drug target proteins Glycerol phosphate lipoteichoic acid synthase (PDB: 2W5Q), ABC transporter (PDB: 1P99) and DNA Gyrase (PDB: 2XCO) from S. aureus. Hex Docking software was used for the docking studies. The interaction mode and binding results can be represented in terms of docking energy. The best binding energies were obtained from the docking of DNA gyrase with Moricin and Cecropin (-702.13 Kcal/mol and -639.39 Kcal/mol) respectively