Efeito antimicrobiano dos óleos essenciais de Cymbopogon martini e Thymus vulgaris e sinergismo dos constituintes eugenol, timol e geraniol frente a isolados bacterianos de origem hospitalar multirresistentes

Abstract

Bacterial resistance to antimicrobials is a serious worldwide public health problem due to its high mortality rate and restricted therapeutic options. Among the common microorganisms associated with resistance mechanisms, it is possible to highlight bacteria of the Enterobacteriacea family, producers of beta-lactamase enzymes, such as extended spectrum (ESBL) and carbapenemases (KPC). Over the years, the search for alternative therapies by medicinal plants has been gradually increasing and, with this, several studies using essential oils (EO) extracted from aromatic and medicinal plants have been showing their antimicrobial activities, as is the case with the EO Thymus vulgaris L. (TO) and Cymbopogon martini (PO), as well as some of their major constituents. The present study aimed to evaluate the antimicrobial activity of TO and PO and synergism of their major constituents (thymol, eugenol and geraniol) against multiresistant bacterial isolates. Bacteria were isolated from clinical samples of patients admitted into the School Hospital of the Federal University of Pelotas - RS, Brazil. Those identified with reduced carbapenemic sensitivity were submitted to phenotypic tests for carbapenemase enzymes detection. The characterization of the EO was performed and determination of its antioxidant activity was done with the Ferric Reducing Antioxidant Power (FRAP) assay. Antimicrobial and synergistic activity of the EO and their major constituents were determined through minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and monitored by inhibitory curves in bacterial growth. FRAP results showed antioxidant activities of the extracts, especially geraniol. All the EOs and their major constituents presented antimicrobial activity. Thymol was the compound with the lowest MIC values, ranging from 3.51 to 9.37 µg mL-1; followed by eugenol with 104.19 µg mL-1. TO showed no antimicrobial activity against the most resistant isolates. According to the synergism results, a synergistic effect was evidenced only in the combination of thymol with eugenol. This study also found that, according to MBC values, thymol, as well as the other major constituents, presented both inhibitory and bactericidal activity against bacterial isolates. These results suggest that the tested EO and their major constituents, especially thymol, present potential as promising antimicrobial agents against multiresistant isolates.