Investigating the antimicrobial properties of Staphylococci-derived compounds against ESKAPE bacteria

Abstract

Klebsiella pneumoniae, Enterococcus faecium, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter cloacae, and Enterobacter aerogenes (ESKAPE) bacterial group is well noted for drug resistance. These strains cause various diseases and in doing so, utilize various ways to resist a broad range of antibiotics. Susceptibility to antibiotics amongst ESKAPE bacteria is rapidly declining, and therefore, there is a need to explore alternative ways to deal with ESKAPE-related conditions by utilizing bacterial compounds. The compounds used in this study were derived from secondary metabolites of Staphylococci stains (S saprophyticus [ATCC 35552], S. aureus [isolated from milk of mastitic cows], and S. epidermidis [ATCC 51625]. These compounds were screened, identified and evaluated for cytotoxicity beforehand. Such compounds included Veratramine, 1,2,6-Hexanetriol, Succinic acid, 4-Methyl-pentyl-amine; from S. saprophyticus, Fluoranthene, 3-Methyl-2-phenyl-1H-pyrrole, and Cyclo (L-Leu-L-Propyl) and from S. epidermidis, Oleamide and Methyl palmitate. However, Fluoranthene is excluded in this study as it previously exhibited cytotoxicity against Vero cells, therefore, is considered unsuitable as a prospective antimicrobial agent. Prior to exploring the antimicrobial properties of Staphylococci-derived compounds, the susceptibility of ESKAPE bacteria was tested against the antibiotic regimens as per South African guidelines. The investigations on antibiotics susceptibility were carried out to compare the susceptibility of ESKAPE bacteria to known antibiotics against Staphylococci-derived compounds. The antimicrobial properties of the compounds were evaluated both qualitatively and quantitatively by TLC bioautography and a broth microdilution method, respectively. In this study, we found that all the compounds did not exhibit any antimicrobial properties against the ESKAPE bacteria except for Succinic acid, which exhibited its efficacy against A. baumannii with a minimum inhibitory concentration (MIC) of 62.5 µg/mL.