Combined Action of Piperitenone Epoxide and Antibiotics Against Clinical Isolates of Staphylococcus aureus and Escherichia coli

Abstract

The aim of this study was to determine the antimicrobial efficiency of piperitenone epoxide (PEO) – a principal component of various aromatic plants’ essential oil – in combination with various antibiotics against 28 strains of Staphylococcus aureus and 10 strains of Escherichia coli isolated from clinical samples. Mentha spicata’s essential oil, initially collected by hydrodistillation, was then subjected to flush column chromatography affording PEO of high purity. Minimum inhibitory concentrations of PEO alone and in combination with various concentrations of antibiotics were assessed using the microdilution method. The combined action was estimated calculating the fractional inhibitory concentration (FIC) index from checkerboard assays. Our results showed that the average minimum inhibitory concentration (mg/l) of PEO alone against E. coli was 512 ± 364.7 μg/ml, which was significantly higher than 172.8 ± 180.7 μg/ml observed for S. aureus. From checkerboard assays, FIC values below the 0.5 index, indicating synergy, were observed for 59% of the drugs tested. Twelve percent of FIC index values were between 0.5 and 1, indicating additive effects, while 21% were indifferent. According to our results, PEO could be a promising antimicrobial compound when combined with specific antibiotics and deserves further study.

Effects of Melaleuca alternifolia Chell (Tea Tree) and Eucalyptus globulus Labill. Essential Oils on Antibiotic-Resistant Bacterial Biofilms

“…Their combined use has shown the capability to reduce the antibiotic concentrations of employees and, consequently, to decrease the toxic effects during the therapy. These results highlight the ability of essential oils to be a potential modulating agent of antibiotic resistance, as has already emerged from other studies [ 45 , 46 , 47 , 48 , 49 ]. The use of natural antimicrobial agents is increasingly expanding, also thanks to new biotechnologies, such as the incorporation of essential oils in polymeric nanoparticles [ 50 ], a technology used to obtain an increase in antibacterial and antioxidant activity, with a reduction of toxic effects and a better penetration into the biofilm [ 51 ].…”

Antibacterial Effect of Eucalyptus Essential Oil

“…Different investigations had discussed the efficacy of essential oils against gram positive and negative bacteria, and showed that gram positive bacteria more susceptible to oils [13][14]. However, in [15], reported different results where EO in combination with antimicrobial drugs considerably reduced the effective doses of the drugs used with E. coli isolates despite relatively high MIC values of this EO. In our study, missing data like the minimum bactericidal concentration were not estimated; more numbers of isolates should be tested to assess the efficacy of EEO and different antibiotics.…”

Essential Oils: A Natural Weapon against Antibiotic-Resistant Bacteria Responsible for Nosocomial Infections

“…Their antibacterial activity has been recently studied against pathogenic bacteria frequently responsible for hospital-acquired infections (HAIs) [ 21 , 22 , 23 , 24 , 25 ]. Recent studies have also highlighted the synergistic action of EOs with other antimicrobial drugs and how these associations could be used to positively modulate the antimicrobial activity of some antibiotics against antibiotic-resistant bacteria, with a consequent decrease in the minimum effective dose of the drugs [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ].…”