Bioactivity screening of Soil bacteria against human pathogens

Abstract

Microorganisms have a profound effect on medical science as they not only infect & cause disease but also produce metabolic products that can cure infections. Soil happens to be a source for a variety of microorganisms. Most of the bacteria, particularly actinomycetes produce biologically active secondary metabolites. Though there are a number of antibiotics available, there is a pressing need for the discovery of new source for antimicrobials against the pathogens due to the development of drug resistance of the pathogenic microorganisms. In addition to, new pathogenic strains are also developing and causing infection to human beings. Bioactive compounds are compounds that are produced by any living organism and are known to exhibit various biological activities both in-vitro & in-vivo.  Bioactivity may be antimicrobial, antineoplastic, anticancerous, immunomodulation, antifertility & others. Soil bacteria were isolated by standard technique and by making use of selective media. The isolates were identified and subjected for preliminary screening to look for their ability to produce bioactive materials. A total of 96 strains were isolated from three different soil samples. 14 of them were found to have antibacterial activity against the human pathogens like Staphylococcus aureus, Streptococcus faecalis, E.coli, Klebsiella aerogenes, Proteus vulgaris, Pseudomonas aureginosa and  Salmonella typhi by preliminary screening. Further the selected (3) bacteria were grown in the suitable culture media for the production of bioactive metabolites by using rotary shake flask. The active metabolites was isolated by solvent extraction and concentrated by evaporation under reduced pressure. The antimicrobial screening of the active metabolites showed prominent effect against the clinical pathogens under the study.