Antibacterial Activity of Selected Essential Oil Compounds Alone and in Combination with β-Lactam Antibiotics Against MRSA Strains

Abstract

This study aimed to determine the effect of selected essential oil compounds (EOCs) on the antibacterial activity of β-lactam antibiotics (βLAs) against methicillin-resistant Staphylococcus aureus (MRSA) strains. The following parameters were studied: antibiotic susceptibility testing, detection of mecA gene and evaluation of genotypic relativity of isolates using molecular techniques, analysis of chemical composition applying Fourier-transform infrared (FTIR) spectroscopy, and determination of antibacterial activity of EOCs alone and in combination with βLAs against MRSA strains using microdilution and checkerboard methods. It was found that all isolates expressed MRSA and resistance phenotypes for macrolides, lincosamides, and streptogramins B. All isolates harbored the mecA gene and belonged to three distinct genotypes. Eight of the 10 EOCs showed efficient antimicrobial activity against the MRSA reference strain. The analysis of interaction between EOCs and βLAs against the MRSA reference strain revealed a synergistic and additive effect of the following combinations: methicillin (Met)-linalyl acetate (LinAc), penicillin G (Pen)-1,8-cineole (Cin), and Pen-LinAc. Analysis of EOC-βLA interactions showed a synergistic and additive effect in the following combinations: Met-LinAc (against low- and high-level βLAs resistance strains), Pen-Cin, and Pen-LinAc (against low-level βLAs resistance strains). It was also confirmed that changes in phosphodiester, -OH, -CH2 and -CH3 groups may change the interactions with βLAs. Moreover, the presence of two CH3O- moieties in the Met molecule could also play a key role in the synergistic and additive mechanism of LinAc action with Met against MRSA strains. Direct therapy using a Met-LinAc combination may become an alternative treatment method for staphylococcal infections caused by MRSA. However, this unconventional therapy must be preceded by numerous cytotoxicity tests.

Phytochemical Profile, Preliminary Toxicity, and Antioxidant Capacity of the Essential Oils of Myrciaria floribunda (H. West ex Willd.) O. Berg. and Myrcia sylvatica (G. Mey) DC. (Myrtaceae)

“…The biological activities of EOs may be related to the presence of certain constituents at a higher content and to the synergistic and/or antagonistic effects exerted by all substances present in the samples [ 113 , 114 , 115 , 116 , 117 , 118 ]. Considering that 1,8-cineole has low toxicity, and the other compounds present at high levels have moderate or high toxicity, the combined effects of the volatile constituents of the EO of M. floribunda may explain its moderate toxicity.…”

Antibacterial Properties of Eucalyptus globulus Essential Oil against MRSA: A Systematic Review

“…This may be attributed to the presence of multiple active antibacterial constituents and interactions between various constituents of both oils [ 39 , 40 ], the combination of which may have various actions, such as increasing the solubility and/or bioavailability of one or more constituents of the oil or acting on different targets, leading to an enhanced antibacterial effect [ 39 ]. Synergy is noted between various agents, such as Olbas (composed of peppermint oil, eucalyptus oil, cajuput oil, juniper berry oil and wintergreen oil) [ 19 ], between tea tree oil and eucalyptus oil [ 7 ], various antibiotics and eucalyptus oil [ 7 , 17 , 23 , 41 ].…”

The Combination of Amoxicillin and 1,8-Cineole Improves the Bioavailability and the Therapeutic Effect of Amoxicillin in a Rabbit Model

“…This aims to enhance their antibacterial activities, in the treatment of vulvovaginal candidiasis, bacterial vaginosis, and acne [ 38 ]. Findings in vitro by Kwiatkowski et al [ 39 ] and those in vitro and in vivo by Hriouech et al [ 40 ] revealed the synergistic effect of 1,8-cineole in combination with beta-lactam antibiotics, including penicillin G and AMX, against MRSA strains.…”