Heather Cavanagh

Evaluation of Common Antibacterial Screening Methods Utilized in Essential Oil Research

Abstract The use of essential oils as therapeutic agents has become increasingly popular; however, research into the antimicrobial activity of these products has been hampered by the lack of standardized and reliable screening methods. The lack of standardized methods also makes direct comparison of results between studies impossible. In this study, the most commonly used antimicrobial assays cited in the literature were evaluated for reliability and their ability to accurately assess, and directly compare, essential oil antimicrobial activity. The methods used were disc diffusion, well diffusion, agar dilution and broth dilution. This study revealed that the disc diffusion, well diffusion and agar dilution methods were unreliable and produced inconsistent results. This was largely due to problems related to achieving stable dispersion of the oils in aqueous media, diffusion of lipophilic constituents in aqueous media and varying methods for determining numbers of viable bacteria remaining after the addition of the oil. An optimized broth dilution method, using 0.02% Tween 80 to emulsify the oils, was developed and shown to be the most accurate method for testing the antimicrobial activity of the hydrophobic and viscous essential oils. When evaluated against a range of oils, this method provided the most reliable and correct results and allowed direct comparison of the antibacterial activity of the test oils, irrespective of viscosity and hydrophobicity.

Antibacterial Activity of Berry Fruits Used for Culinary Purposes

Increasing interest in the health benefits of various culinary berries has led to investigation of their antibacterial activity. Commercial raspberry, blackcurrant, cranberry, and blackberry cordials (100% fruit) as well as fresh berries were assessed for their ability to inhibit the growth of various bacteria and the yeast Candida albicans. Three of the six raspberry cordials and the blackcurrant cordial inhibited all 12 bacteria and C. albicans at dilutions of 1:5. Bacteria showed varying susceptibilities to the remaining cordials. All cordials inhibited the growth of Mycobacterium phlei. Of the fresh berries, mulberries and boysenberries did not inhibit any bacteria, and the remaining berries inhibited the growth of varying numbers of bacteria. There was no correlation between gram-positive or gram-negative bacterial status and susceptibility to the berries. It is suggested that the antibacterial activity of these berries may be of benefit as a means of water purification for suspect water supplies or to enhance shelf life when incorporated into food products.

Antiparasitic activity of two Lavandula essential oils against Giardia duodenalis, Trichomonas vaginalis and Hexamita inflata.

Two essential oils derived from Lavandula angustifolia and Lavandula × intermedia were investigated for any antiparasitic activity against the human protozoal pathogens Giardia duodenalis and Trichomonas vaginalis and the fish pathogen Hexamita inflata: all of which have significant infection and economic impacts. The study has demonstrated that low (≤1%) concentrations of L. angustifolia and L. × intermedia oil can completely eliminate T. vaginalis, G. duodenalis and H. inflata in vitro. At 0.1% concentration, L. angustifolia oil was found to be slightly more effective than L × intermedia oil against G. duodenalis and H. inflata. The potential applications are discussed.

Analysis of essential oil of Satureja thymbra by hydrodistillation, thermal desorber, and headspace GC/MS techniques and its antimicrobial activity.

The essential oil composition of Satureja thymbra was analyzed by direct thermal desorber and Headspace GC/MS analysis methods. Its constituents were determined to be mainly carvacrol (40.15%), γ-terpinene (26.56%), p-cymene (16.39%), and thymol (13.16%). The other techniques, thermal desorber and Headspace GC/MS, were used for the plant leaves at three different temperature, which showed similar results. The thermal desorber GC/MS gave better and more sensitive results than Headspace GC/MS. The essential oil was found to be active against the bacteria Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Shigella sonnei, and Staphylococcus aureus and the yeast Candida albicans.

Riverina high school students views of biotechnology

Electronic Journal of Biotechnology ISSN: 0717-3458 Vol.8 No.2, Issue of August 15, 2005

Antifungal Activity of Australian Grown Lavandula spp. Essential Oils Against Aspergillus nidulans, Trichophyton mentagrophytes, Leptosphaeria maculans and Sclerotinia sclerotiorum

Abstract In this study the antifungal activity of eight essential oils and three hydrosols (aqueous distillates) from Australian grown lavenders was determined. The oils and hydrosols were assayed against four fungi, Aspergillus nidulans, Trichophyton mentagrophytes, Leptosphaeria maculans and Sclerotinia sclerotiorum, using a disc diffusion method. No evidence of antifungal activity was observed with any of the hydrosols. In contrast, all oils displayed some antifungal activity. Lavandula angustifolia and the three examples of Lavandula x intermedia oil demonstrated the greatest effect against A. nidulans and T. mentagrophytes while L. stoechas was particularly effective against the two agricultural fungi, L. maculans and S. sclerotiorum. No significant difference was observed between the antifungal activity of L. angustifolia oils derived from European and Australian grown plants. These results suggest that the oils from various Lavandula species may be useful in the treatment of fungal infections.

Microsphere‐liposome complexes protect adenoviral vectors from neutralising antibody without losses in transfection efficiency, in‐vitro

Adenoviral vectors have been commonly used in gene therapy protocols but the success of their use is often limited by the induction of host immunity to the vector. Following exposure to the adenoviral vector, adenoviral‐specific neutralising antibodies are produced, which limits further administration. This study examines the effectiveness of a novel combination of microspheres and liposomes for the shielding of adenovirus from neutralising antibodies in an in‐vitro setting. We show that liposomes are effective in the protection of adenovirus from neutralising antibody and that the conjugation of these complexes to microspheres augments the level of protection. This study further reveals that previously neutralised adenovirus may still be transported into the cell via liposome‐cell interactions and is still capable of expressing its genes, making this vector an effective tool for circumvention of the humoral immune response. We also looked at possible side effects of using the complexes, namely increases in cytotoxicity and reductions in transfection efficiency. Our results showed that varying the liposome:adenovirus ratio can reduce the cytotoxicity of the vector as well as increase the transfection efficiency. In addition, in cell lines that are adenoviral competent, transfection efficiencies on par with uncomplexed adenoviral vectors were achievable with the combination vector.

The effect of Leptospermum petersonii essential oil on Candida albicans and Aspergillus fumigatus

A variety of assays were utilized to determine the effects of Leptospermum petersonii essential oil on both Candida albicans and Aspergillus fumigatus. Hyphal morphology, susceptibility of spheroplasts and uptake of propidium iodide following exposure to the oil suggest that the mode of action of L. petersonii essential oil is through direct disturbance of the fungal cell membrane. Data also confirms that the volatile component of the oil is highly antifungal, independent of direct contact between the liquid oil and the fungal membrane. The degree of inhibition was greater when fungi were directly exposed to oil volatiles compared to pre-inoculation exposure of oil volatiles into the agar. It is likely that the essential oil volatiles are acting both directly and indirectly on the fungi to produce growth inhibition.

Cell contact dependent extended release of adenovirus by microparticles in vitro

Adenoviral vectors remain one of the most promising methods of gene delivery but are plagued by several inherent problems including immune inactivation and transient expression. This paper reports a novel microparticle-based delivery system for adenovirus that allows high uptake of virus, stable complex formation and extended release. In addition, this microparticle/adenovirus complex has been demonstrated to only release virus upon cell contact. The significant clinical implications of this delivery system are discussed.

Genetic characterization of equine adenovirus type 1

Two known serotypes of equine adenovirus (EAdV), equine adenovirus type 1 (EAdV-1) and equine adenovirus type 2 (EAdV-2) have been isolated from horses. EAdV-1 is predominantly associated with upper respiratory tract infections while EAdV-2 appears to be associated with gastrointestinal infections in horses. In this report the EAdV-1 genome has been sequenced for the first time. The EAdV-1 genome encoded genes are characteristic of the Mastadenovirus genus such as protein V and IX. Unexpectedly, phylogenetic reconstructions also revealed a close relationship between EAdV-1 and two recently characterized bat adenoviruses. The results of this study suggest that EAdV-1 may share a common ancestor with canine and bat adenoviruses.