Antimicrobial profile of crude extracts by actinobacteria isolated from Caatinga rhizosphere

Abstract

The increasing emergence of micro-organisms strains resistant to antibiotics commonly used in the various human and veterinary medicine therapy has been attracting the attention to the need for isolation and identification of novel antimicrobial compounds, as well as the knowledge of the mode action of these novel compounds that act effectively in the control of these multi-resistant strains. Undoubtedly, the chemistry of microbial natural products is an excellent source to search for substances with potent antimicrobial activity. Historically, more than 60% of the main antibiotic marketed today are produced by Actinomycetes or their structures were inspired by these compounds. Despite this historical success in recent years the discovery of new chemical structures with antimicrobial activity had a significant decline, mainly due to the methodology of repetition leading to the re-insulation structure known compounds. Thus this research project aims to explore the potential of isolated actinomycetes of the Caatinga biome, as a source of novel bioactive substances. The Caatinga is unique in the world and its micro-organisms are adapted to high temperatures, UV radiation excess, water stress and shortage of nutrients. Thus, these micro-organisms have the potential to make unique physiological and biochemical properties for the production of secondary metabolites. The extracts generated will undergo diffusion disk tests using as biological target bacteria of the genus Staphylococcus sp., Escherichia coli and Streptococcus sp., isolated from cows with pre-clinical mastitis cases in order to identify extracts and compounds isolates that can be used against mastitis. Bovine mastitis is the main disease that affects the dairy herd in Brazil and in the world, and needs more effective treatments for the control of the main pathogens.