Katie Laird

Vapour phase: a potential future use for essential oils as antimicrobials?

Essential oil (EO) vapours have been known for their antimicrobial properties since the 4th century B.C.; however, it was not until the early 1960s that research into the potential of these volatile oils was explored. More recently, the use of EOs such as tea tree, bergamot, lavender and eucalyptus in vapour form has been shown to have antimicrobial effects against both bacteria and fungi, with range of methods being developed for dispersal and efficacy testing. To date, many applications for EO vapours as antimicrobials have been identified including in the food and clinical arenas.

Evaluating the link between the management of clinical waste in the National Health Service (NHS) and the risk of the spread of infections: A case study of three hospitals in England

This study aimed to evaluate waste management practices in three case study NHS Trusts in England and the potential risks of the spread of pathogens causing healthcare associated infections (HCAIs). Using a combination of microbiological techniques, interviews and questionnaire surveys, four target microbes were studied, namely: meticillin resistant Staphylococcus aureus (MRSA), meticillin sensitive Staphylococcus aureus (MSSA), Clostridium difficile (C. difficile) and vancomycin-resistant enterococci (VRE). Waste Flow Diagrams (WFDs) were used to map the flow of the waste. While there was a perceived link between the management of the waste and the spread of the microbes by staff, none of the target organisms were isolated. The findings suggest that when the waste is properly contained and managed that it should not pose a significant risk in terms of the spread of the four bacteria tested in this study. In addition, the results demonstrate that there is a need for staff perceptions and beliefs to be addressed in the development of policies and training related to infection control and its link to waste management.

A Multifactorial Comparison of Ternary Combinations of Essential Oils in Topical Preparations to Current Antibiotic Prescription Therapies for the Control of Acne Vulgaris-Associated Bacteria.

Acne vulgaris, a chronic condition associated with overgrowth of Propionibacterium acnes and Staphylococcus epidermidis, is commonly treated with antibiotics. However, the emergence of antibiotic resistance has resulted in a need for alternative therapies. The aim of this study is to develop a topical preparation incorporating essential oils (EOs) for use against acne‐associated bacteria and assess its efficacy against prescription therapies Dalacin T and Stiemycin. Antimicrobial screening of rosewood, clove bud and litsea EOs was conducted before interactions between binary and ternary combinations were determined against P. acnes and S. epidermidis (type and clinical isolates) using minimum inhibitory concentrations and fractional inhibitory concentrations. The EOs were characterised by both gas chromatography–mass spectrometry and nuclear magnetic resonance. A combination of 0.53 mg/mL litsea, 0.11 mg/mL rosewood and 0.11 mg/mL clove bud was formulated into herbal distillates and compared with Dalacin T and Stiemycin against antibiotic sensitive and resistant isolates (erythromycin). The distillate with EO had synergistic activity against P. acnes (7log10 reduction) and indifferent activity against S. epidermidis (6log10 reduction); antimicrobial activity was either significantly (p ≤ 0.05) more antimicrobial or equivalent to that of Dalacin T and Stiemycin. This formulation may serve as a valuable alternative for the control of acne vulgaris‐associated bacteria. Copyright

The effect of low-temperature laundering and detergents on the survival of Escherichia coli and Staphylococcus aureus on textiles used in healthcare uniforms

To determine the survival of Escherichia coli and Staphylococcus aureus on cotton and polyester and the effectiveness of low‐temperature laundering and detergents on the removal of micro‐organism from healthcare laundry.

Synchronous application of antibiotics and essential oils: dual mechanisms of action as a potential solution to antibiotic resistance

Abstract Antibiotic resistance has increased dramatically in recent years, yet the antibiotic pipeline has stalled. New therapies are therefore needed to continue treating antibiotic resistant infections. One potential strategy currently being explored is the use of non-antibiotic compounds to potentiate the activity of currently employed antibiotics. Many natural products including Essential Oils (EOs) possess broad spectrum antibacterial activity and so have been investigated for this purpose. This article aims to review recent literature concerning the antibacterial activity of EOs and their interactions with antibiotics, with consideration of dual mechanisms of action of EOs and antibiotics as a potential solution to antibiotic resistance. Synergistic interactions between EOs and their components with antibiotics have been reported, including several instances of antibiotic resensitization in resistant isolates, in support of this strategy to control antibiotic resistance. However, a lack of consistency in methods and interpretation criteria makes drawing conclusions of efficacy of studied combinations difficult. Synergistic effects are often not explored beyond preliminary identification of antibacterial interactions and mechanism of action is rarely defined, despite many hypotheses and recommendations for future study. Much work is needed to fully understand EO-antibiotic associations before they can be further developed into novel antibacterial formulations.

Chemical Synthesis of Copper Nanospheres and Nanocubes and Their Antibacterial Activity Against Escherichia coli and Enterococcus sp.

The interest in synthesising inorganic nanomaterials for biological applications has increased in recent years, especially for antibacterial purposes. In the present study, spherical and cube-shaped copper nanoparticles were synthesised by a chemical reduction method and their efficacy as antimicrobial agents against both Gram-negative (Escherichia coli) and Gram-positive (Enterococcus sp.) organisms investigated. The nanoparticles were characterised using ultraviolet/visible spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Copper nanocubes were found to be more antimicrobial when compared with copper nanospheres, and it is postulated that whilst both sets of nanoparticles have similar total surface areas, the different shapes have different active facets and surface energies, which may lead to differing bactericidal behaviour.

Washing uniforms at home: adherence to hospital policy.

Infection control is a priority for all hospitals to reduce the spread of healthcare-associated infections (HCAIs). Textiles especially uniforms, are a possible route of HCAI transmission. There are protocols to ensure hospital laundry services meet accepted standards, however healthcare uniforms are laundered by staff at home and variations in practice occur. A questionnaire was used to conduct a service evaluation at four hospitals in different NHS trusts to determine how closely healthcare staff followed hospital guidelines on laundering and aftercare of uniforms at home. Responses showed that not all staff followed these guidelines; 44% of staff washed their uniforms below the recommended temperature of 60°C, which presents a potential route for cross-contamination and infection.

Structure-activity modelling of essential oils, their components, and key molecular parameters and descriptors

Many essential oil components are known to possess broad spectrum antimicrobial activity, including against antibiotic resistant bacteria. These compounds may be a useful source of new and novel antimicrobials. However, there is limited research on the structure-activity relationship (SAR) of essential oil compounds, which is important for target identification and lead optimization. This study aimed to elucidate SARs of essential oil components from experimental and literature sources. Minimum Inhibitory Concentrations (MICs) of essential oil components were determined against Escherichia coli and Staphylococcus aureus using a microdilution method and then compared to those in published in literature. Of 12 essential oil components tested, carvacrol and cuminaldehyde were most potent with MICs of 1.98 and 2.10 mM, respectively. The activity of 21 compounds obtained from the literature, MICs ranged from 0.004 mM for limonene to 36.18 mM for α-terpineol. A 3D qualitative SAR model was generated from MICs using FORGE software by consideration of electrostatic and steric parameters. An r2 value of 0.807 for training and cross-validation sets was achieved with the model developed. Ligand efficiency was found to correlate well to the observed activity (r2 = 0.792), while strongly negative electrostatic regions were present in potent molecules. These descriptors may be useful for target identification of essential oils or their major components in antimicrobial/drug development.

Application of a Novel Tongue Resin Replication

Aims: Biofilms present a strategy for microorganisms to survive and resist adverse conditions. In order to further our understanding of this resistance mechanism, it is of much importance to develop new methodologies in order to assess such biofilm activities. One of the most defined biofilms is dental plaque. However, the oral cavity contains a different class of biofilm, the precise structural nature of which is dependent on its site of development. Indeed, tongue-coated biofilms have remained a focus for in vitro studies, especially since they represent the major source of oral malodor. The aim of this research was to investigate the growth of a biofilm on a tongue replication constructed from a resin material, and its use in further experimental investigations. Methods: The model used for this study involved an adapted CDC biofilm reactor in order to achieve this; Staphylococcus aureus was used as the test organism. Results: Biofilm culturing techniques employed demonstrated a positive growth from the microbes Short Research Article Bernardi et al.; BMRJ, 17(1): 1-8, 2016; Article no.BMRJ.28606 2 retrieved from the tongue-impressed resin material. Moreover, results acquired confirmed that the resin-based tongue replication harbored significantly greater levels of S. aureus than those of unimpressed resin, plastic and stainless steel controls. Conclusions: Therefore, this study provides evidence that the employment of a CDC biofilm reactor in combination with a resin tongue device creates an oral biofilm model which provides valuable information regarding our understanding of how the roughness of the dorsal lingual surface affects microbial populations in patients suffering from oral malodor.

Morphological changes in Enterococcus faecium on exposure to citrus essential oils in vapor phase as determined by TEM, SEM and AFM

The antimicrobial effects of essential oils in vapor phase have been previously reported although the mechanism whereby they bring about their effect continues to be investigated. Morphological changes give some indication of the extent of the damage to cells brought about by exposure to essential oils and may provide a means of substantiating the physiological and biochemical changes that are integral to the antimicrobial effect. In this study, the morphological changes that occur during exposure of Enterococcus faecium to a Citrus essential oil in vapor phase has been investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). TEM shows membrane damage, vacuole formation and leakage of cytoplasmic material, SEM shows deformation of shape, whereas AFM, which gives the most information, confirms the deformation, which could be seen even after 15 minutes exposure using this method.