engleski

Antibacterial effect of Centaurea ragusina essential oils against extended-spectrum beta-lactamases (ESBLs) producing strains and their synergistic potential with antibiotics

The emergence of extended-spectrum beta-lactamase (ESBLs)-producing Gram-negative bacteria, is now a critical concern for the development of therapies against bacterial infection. Despite the excellent antibacterial activity of many plant secondary metabolites and the ability of some of them to modify the antimicrobial resistance associated with multiresistant strain and efflux pumps, plants are still a substantially untapped source of antimicrobial agents. In this study, we examined the antimicrobial effect of Centaurea ragusina essential oil and conventional antibiotics when used in association against eleven extended-spectrum beta-lactamases producing strains as well its ability to improve antibiotics action. Antimicrobial effects of the volatile samples were investigated by the disc diffusion and microdilution assays. Addicionally, efficacy of essential oil combined with antibiotics was determined by checkboard assay. The phytochemical profile determined by GC and GC-MS, were complex, with sesquiterpenes the most abundant class of compound. Nonterpene hydrocarbons were also identified in high quantities, while aldehydes, alcohols, esters and other compounds were identified in lower quantities. The volatile oils displayed great antibacterial potential with MIC values ranging from 8 to 128 g/ml against ESBL producing Gram-negative bacteria. Out of 124 combinations tested between essential oil and antibiotics, 68% showed synergism in combination with ampicillin, tetracyclines, gentamicin and cefalosporines. These findings are very promising since the use of these combinations for nosocomial infections treatment is likely to reduce the minimum effective dose of the antibiotics, thus minimizing their possible toxic side effects and treatment cost.

Centaurea ragusina; antimicrobial; GC-MS; extended-spectrum beta-lactamase

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