Elsevier

Burns

Volume 30, Issue 8, December 2004, Pages 772-777
Burns

The effect of essential oils on methicillin-resistant Staphylococcus aureus using a dressing model

https://doi.org/10.1016/j.burns.2004.06.006Get rights and content

Abstract

Patchouli, tea tree, geranium, lavender essential oils and Citricidal™ (grapefruit seed extract) were used singly and in combination to assess their anti-bacterial activity against three strains of Staphylococcus aureus: Oxford S. aureus NCTC 6571 (Oxford strain), Epidemic methicillin-resistant S. aureus (EMRSA 15) and MRSA (untypable). The individual essential oils, extracts and combinations were impregnated into filter paper discs and placed on the surface of agar plates, pre-seeded with the appropriate strain of Staphylococcus. The effects of the vapours of the oils and oil combinations were also assessed using impregnated filter paper discs that were placed on the underside of the Petri dish lid at a distance of 8 mm from the bacteria. The most inhibitory combinations of oils for each strain were used in a dressing model constructed using a four layers of dressings: the primary layer consisted of either Jelonet™ or TelfaClear™ with or without Flamazine™; the second was a layer of gauze, the third a layer of Gamgee and the final layer was Crepe bandage. The oil combinations were placed in either the gauze or the Gamgee layer. This four-layered dressing was placed over the seeded agar plate, incubated for 24 h at 37 °C and the zones of inhibition measured. All experiments were repeated on three separate occasions. No anti-bacterial effects were observed when Flamazine™ was smeared on the gauze in the dressing model. When Telfaclear™ was used as the primary layer in the dressing model compared to Jelonet™, greater zones of inhibition were observed. A combination of Citricidal™ and geranium oil showed the greatest-anti-bacterial effects against MRSA, whilst a combination of geranium and tea tree oil was most active against the methicillin-sensitive S. aureus (Oxford strain). This study demonstrates the potential of essential oils and essential oil vapours as antibacterial agents and for use in the treatment of MRSA infection.

Introduction

Despite major advances in wound management, infection still remains an important factor in wound healing. In burns, approximately 75% of deaths are due to complications with sepsis resulting from wound infection [1]. Among other adverse effects, infection delays healing, contributes to graft failure and can increase the depth of a burn. Approximately 30% of burn wounds become colonised with Staphylococcus aureus [2] and outbreaks of methicillin-resistant S. aureus (MRSA) have created major problems for burn units and intensive care units in terms of cross-infection and rehabilitation of the patient due to imposed barrier nursing [3]. Some MRSA strains, termed epidemic MRSA (EMRSA), have the ability to spread rapidly among patients and the dominant clonal EMRSA types 15 and 16 are problematic in the UK [4], [5]. A new strain, EMRSA 17, has recently been described in the UK [6]. Whilst vancomycin is one of the few remaining effective systemic antibiotics available for treatment, resistance has been reported and there is major concern that total antibiotic-resistant strains may emerge in the immediate future [7]. At present, topical anti-microbial therapy is the single most important component of wound care to prevent infection [8] and in hospitalised burn patients, Flamazine™ is by far the most frequently used topical prophylactic agent [9] but does not always penetrate into the wound [10] and cannot be used to eradicate carriage from the patient or the environment.

Alternative therapies are being sought for treatment of MRSA and one area of interest is the use of essential oils. MRSA is susceptible to tea tree oil [11] but there are concerns about its toxicity [12]. Tea tree oil has been accepted as a powerful antibacterial agent [13] and is sold commercially in a wide range of products. There are hundreds of other essential oils available for use, many with known antibacterial properties. These oils contain numerous constituents that contribute to the characteristic odour and medicinal effects. The major chemical components that account for the pleasant aromatic odours are primarily terpenenes, monoterpenes and linalool [14]. The presence and quantity of the various components varies between oils and determines the individuality of the oil [15]. Although essential oils are known for their antimicrobial properties, medical teams rarely use them. This is primarily due to lack of scientific evidence of their efficacy, toxicity issues and the availability of conventional therapy. In this study, a range of essential oils and extracts were tested for their anti-bacterial properties using an in vitro dressing model to assess the anti-microbial action of the vapours.

Section snippets

Bacterial strains

Three strains of S. aureus were used: an antibiotic-susceptible strain, S. aureus NCTC 6571 (Oxford strain); a methicillin-resistant S. aureus (non-typable) and a methicillin-resistant S. aureus (phage type15). The two strains of MRSA were isolated from the wounds of two burn patients on the Burns Unit, Withington Hospital, Manchester, UK.

Essential oils

Four essential oils were used in the study: tea tree (Melaleuca alternifolia), patchouli (Pogostemon cablin), lavender (Lavendula officinalis), geranium (

Antibacterial action of single oils: direct contact

All bacterial strains showed some susceptibility to each individual essential oil when tested in direct contact using the disc diffusion method. The size of the zone of inhibition varied depending upon the oils and the strain of S. aureus used. Tea tree oil gave the largest zones of inhibition when tested against MRSA than any of the other oils. MRSA appeared to be more susceptible to tea tree oil than the Oxford Staphylococcus. Patchouli, lavender, geranium and Citricidal™ inhibited growth of

Discussion

This study highlights the potential use of essential oil impregnated dressings for treating wounds infected with MRSA. Although the results are very promising, one must advise caution with their use on burned or open wounds. The toxicity and effect on re-epithelialisation of these compounds have not been investigated in this study: these are important issues for future research.

Several methods were tested to screen the oils for their antimicrobial effect. In previous studies, we have used

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