In vitro antibacterial screening of methanolic extract of whole body tissue and ethylene diamine tetra acetate (EDTA) extract of cuttlebone of Sepia pharaonis (Ehrenberg, 1831) against selected clinical isolates

The need for the discovery of new and novel antibiotics is imperative because evidence suggests that development and spread of resistance to any new antimicrobial agent is inevitable. In the present study, the in vitro antibacterial activity of methanolic extract of whole body tissue and ethylene diamine tetra acetate (EDTA) extract of cuttlebone (polysaccharide) of Sepia pharaonis was investigated against ten bacterial species including Gram-positive species (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative species (Salmonella typhi, Klebsiella pneumoniae, Vibrio cholerae, Klebsiella oxytoca, Escherichia coli, Salmonella paratyphi, Vibrio parahaemolyticus and Proteus mirabilis) with different concentrations such as 25, 50, 75 and 100% using disc diffusion method. The highest inhibition zone was recorded against P. mirabilis for methanolic extract (18.3±0.1 for 100% concentration) and against S. pyogenes for EDTA extract (polysaccharide) (15.5±0.06 for 100% concentration) of cuttlebone. But the activity was totally absent in negative control. For minimum inhibitory concentration (MIC) technique, various ranges of concentrations between 20 and 100 mg/ml were prepared and tested. MIC values were found ranging from 40 and 100 mg/ml. All assays were carried out in triplets. A wide spectral and concentration dependent antibacterial activity was recorded in both extracts. Key words: Antibacterial activity, polysaccharide, cuttlebone, methanolic extract, ethylene diamine tetra acetate (EDTA), minimum inhibitory concentration (MIC).