Antibacterial activity of Thymus vulgaris essential oil alone and in combination with cefotaxime against bla_ESBL producing multidrug resistant Enterobacteriaceae isolates

Abstract

The aim was to evaluate the susceptibility of bla_ESBL producing Enterobacteriaceae to Slovakian Thymus vulgaris essential oil (TVEO) alone and in combination with cefotaxime (CTX). TVEO composition was determined by gas chromatograph-mass spectrometer (GC/MS). Susceptibility to 21 antibiotics was determined by disc diffusion assay. Genes characterization for resistance to β-lactams was accomplished by polymerase chain reaction (PCR). The antibacterial activity was investigated by standard methods. The synergistic interaction was determined by checkerboard test. Thymol (34.5%), p-cymene (22.27%) and linalool (5.35%) were the major components present in the TVEO. The identified strains were multi-drug resistant (MDR). TVEO showed high activity against all MDR strains, including bla_ESBL producing isolates, with inhibition zones and MIC values in the range of 24–40 mm/10μL and 2.87–11.5 μg/mL, respectively. TVEO in combination with CTX showed a synergistic action against bla_SHV-12 producing Escherichia coli (FICI 0.28) and an additive effect vs ESBL producing Enterobacter cloacae (FICI 0.987).

Keywords:

• Thymus vulgaris
• essential oil
• antibacterial-resistance
• Enterobacteriaceae
• ESBL
• synergism