Role of Direct Bioautographic Method for Detection of Antistaphylococcal Activity of Essential Oils

Abstract

The aim of the present study was the chemical characterization of some traditionally used and therapeutically relevant essential oils (thyme, eucalyptus, cinnamon bark, clove, and tea tree) and the optimized microbiological investigation of the effect of these oils on clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA). The chemical composition of the oils was analyzed by TLC, and controlled by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The antibacterial effect was investigated using a TLC-bioautographic method. Antibacterial activity of thyme, clove and cinnamon oils, as well as their main components (thymol, carvacrol, eugenol, and cinnamic aldehyde) was observed against all the bacterial strains used in this study. The essential oils of eucalyptus and tea tree showed weak activity in the bioautographic system. On the whole, the antibacterial activity of the essential oils could be related to their most abundant components, but the effect of the minor components should also be taken into consideration. Direct bioautography is more cost-effective and better in comparison with traditional microbiological laboratory methods (e.g. disc-diffusion, agar-plate technique).

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

“…All investigations, except for the fruit oil tested by Mulyaningsih et al, 2011 [ 25 ], found that 1,8 cineole was the main component of the extracts, with percentage values ranging from 32.19% [ 28 ] to 86.51% [ 25 ]. The values for 1,8 cineole were 84.8%, as per Acs et al, 2016 [ 13 ], 81.93%, as per Hamoud et al, 2012 [ 19 ], 84.2%, as per Horvath et al, 2011 [ 22 ], 86.51%, as per Mulyaningsih et al, 2010 [ 25 ], 32.19%, as per Salem et. al.…”

“…Six studies studied the chemical composition of the oil using gas chromatography/mass spectrometry (GC/MS) [ 13 , 19 , 22 , 25 , 26 , 30 ] and one study used gas chromatography alone [ 28 ]. The composition of the oils varied between studies, between oils extracted from different parts of the plant and between various plant stages.…”

Chemical Fingerprinting of Medicinal and Aromatic Plant Extracts: HPTLC Bioautographic Assays as Preliminary Research Tool to Match Chemical and Biological Properties

“…solvent, sample application, compound resolution, type of microorganism, incubation time, etc. may strongly influence the result [8]. The same considerations could be made for antioxidant tests [10].…”

“…fractions and bioactive molecules with important applicative relapses, from those therapeutic as well as nutraceutical to that phytoiatric ones, where the use of natural compounds for plant defense or bio-stimulants for improving cultivated plants yield and quality is strongly demanded for preventing environmental problems and improving integrated agriculture. All these aspects are linked by the common target to answer the increasing demand of natural products, often due to the fact that the use of drugs and synthetic agro-pharmaceuticals in human medicine and agriculture respectively cause selective pressure leading to the spread of resistant etiologic mutants and weakness of innate defense capacities [8].…”

“…The most used tests applied to TLC plates regard antimicrobial (antibacterial and antifungal) assays and antioxidant (DPPH, ABTS, for e.g.) ones [8,10]. Test microorganism cultures are capable of growing directly on the TLC plate, so each step of the assay is performed on the sorbent.…”