Metabolite extraction from environmental bacterial isolates showing antimicrobial properties against eskape pathogens

Antibiotic resistance is a growing concern resulting in tens of thousands of deaths annually worldwide. Antibiotic resistance in pathogenic fungi and bacteria is due in large part to the overuse and misuse of antibiotics in agriculture and medicine. Although antibiotic resistance is rising in most bacteria, some pathogens are more concerning than others. ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) include bacteria of major concern due to their unique virulence traits and multiple antibiotic resistance factors. New approaches must be used to address this crisis including discovery of novel antimicrobials. We aimed to identify the antibiotic compounds produced by two bacterial isolates against ESKAPE pathogens. Bacterial isolates derived from dairy farm samples are of particular interest, including isolate 5 from dairy farm feed and isolate 8d from manure. Bacterial isolate 5 antagonized growth of Staphylococcus aureus, while isolate 8d inhibited growth of Bacillus cereus (although not an ESKAPE pathogen, this species is of interest due to its role in infections and antimicrobial resistance potential). The zones produced by isolates 5 and 8d were extracted for chemical analysis to identify the characteristics of the metabolites. Both metabolites of interest were found to be nonpolar and contain conjugated pi systems as well as oxidizable compounds. Isolate 5 produced metabolites containing alcohol and ester groups, and isolate 8d produced metabolites containing alcohol groups. BLAST data from primers of the ITS region identified isolate 5 as Bacillus pumilus strain 145 and isolate 8d as Bacillus thuringiensis FDAARGOS_971. By preliminarily identifying these antimicrobials, future studies can identify the exact compound being produced by the isolates against their prospective ESKAPE pathogen.