As the issue of antimicrobial resistance continues to grow, there is a renewed interest in deriving antimicrobial products from natural compounds, particularly extracts from plant materials. This paper describes how essential oil can be extracted from the common herb, thyme ( Thymus vulgaris ) in the classroom. Subsequently, the extract can be tested for its antimicrobial activity. A number of variables are suggested.

Oral health status declines with age and as a result the need for removable prostheses increases. Oral health is a reflection of one’s general health, affecting the ability of an individual to eat and speak, and contributes significantly to a sense of confidence and well-being. Currently, there are 15 million denture wearers in the UK, representing a significant consumer base and a special healthcare consideration. The microbiology of denture plaque has received little attention in comparison with dental plaque, yet it differs in location and composition. Denture plaque and poor denture hygiene is associated with stomatitis (Candida infection), may also serve as a reservoir of potentially infectious pathogens, and may contribute to oral malodour and to caries and periodontitis in people who have remaining natural teeth. Oral bacteria have been implicated in bacterial endocarditis, aspiration pneumonia, gastrointestinal infection and chronic obstructive pulmonary disease, among others, and dentures offer a reservoir for microorganisms associated with these infections. An effective oral hygiene regimen is important to control denture plaque biofilm and contributes to the control of associated oral and systemic diseases.

Substratum surface roughness has a well documented effect on the retention of microorganisms. Implications of this encompass problems in hygiene, infection, fouling, equipment function, corrosion and cleanabil‐ity. This paper reviews methods used for visualising surface topography and measuring roughness which are pertinent to microbiologists, and notes limitations of some of the descriptors of surface roughness. A major issue is the scale on which the surface defects are examined: measurements may now be made in nanometers, but the significance of surface texture at this scale in terms of microbial retention has yet to be investigated in detail. Stainless steel and ceramics are commonly used as hygienic food preparation surfaces. Their wear has been visualised, with roughness measured on a nanometer scale using the atomic force microscope (AFM), and the effect on surface wear of cleanability using microbial and organic soil investigated. Surface analytical methods such as X‐ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectroscopy (ToFSIMS) provided information on the chemical structure at the uppermost atomic layer and demonstrate that microorganisms were removed more rapidly than organic material from the worn surfaces, and that organic soil conditioned the surfaces prior to microbial contamination. On this scale, the dimensions of surface defects were more suited to soil retention than to microbial cell retention. Traditional microscopic methods were not able to differentiate adequately between soil and microbial removal. Surface analytical techniques provide the opportunity to measure and visualise surface roughness and its effect on microbial and organic soiling on a hitherto unavailable level of detection.

Materials that confer antimicrobial activity, be that by innate property, leaching of biocides or design features (e.g., non-adhesive materials) continue to gain popularity to combat the increasing and varied threats from microorganisms, e.g., replacing inert surfaces in hospitals with copper. To understand how efficacious these materials are at controlling microorganisms, data is usually collected via a standardised test method. However, standardised test methods vary, and often the characteristics and methodological choices can make it difficult to infer that any perceived antimicrobial activity demonstrated in the laboratory can be confidently assumed to an end-use setting. This review provides a critical analysis of standardised methodology used in academia and industry, and demonstrates how many key methodological choices (e.g., temperature, humidity/moisture, airflow, surface topography) may impact efficacy assessment, highlighting the need to carefully consider intended antimicrobial end-use of any product.

Management of oral candidosis, most frequently caused by Candida albicans, is limited due to the relatively low number of antifungal drugs and the emergence of antifungal tolerance. In this study, the antifungal activity of a range of commercial essential oils, two terpenes, chlorhexidine and triclosan was evaluated against C. albicans in planktonic and biofilm form. In addition, cytotoxicity of the most promising compounds was assessed using murine fibroblasts and expressed as half maximal inhibitory concentrations (IC50). Antifungal activity was determined using a broth microdilution assay. The minimum inhibitory concentration (MIC) was established against planktonic cells cultured in a range of concentrations of the test agents. The minimal biofilm eradication concentration (MBEC) was determined by measuring re-growth of cells after pre-formed biofilm was treated for 24 h with the test agents. All tested commercial essential oils demonstrated anticandidal activity (MICs from 0.06% (v/v) to 0.4% (v/v)) against planktonic cultures, with a noticeable increase in resistance exhibited by biofilms (MBECs > 1.5% (v/v)). The IC50s of the commercial essential oils were lower than the MICs, while a one hour application of chlorhexidine was not cytotoxic at concentrations lower than the MIC. In conclusion, the tested commercial essential oils exhibit potential as therapeutic agents against C. albicans, although host cell cytotoxicity is a consideration when developing these new treatments.