The role of materials and surfaces in the transmission of bacteria in public places

This research project is a study into the bacteria found in schools and measures that can be taken to reduce the transmission from person to person. This project has been carried out in collaboration with the Luxembourg Institute of Science and Technology (LIST). The first stage of the project identified the bacteria in the school with DNA sequencing. While the majority of the bacteria were harmless, Staphylococcus saprophyticus (a cause of urinary tract infections) was identified. In addition, Propionibacterium acnes was found as well as a bacteria belonging to the genus Neisseria (which might provoke meningitis, a sexually-transmitted disease, and other diseases). The project continued with tests on the survival of bacteria on a range of surfaces, and in particular on various soft and hard woods, copper and plastic. The results show a very quick death rate for the bacteria on pine (nearly all gone after 15 minutes). Plastic was the worst performer, with bacteria still present on the plastic surface after more than 10 hrs. The project attempted to identify the compounds in wood that might contribute to its antibacterial properties. Solutions of wood extracts were prepared by soaking sawdust in physiological serum and in ethanol. The water-based solutions had little effect, while the ethanol based solutions did reduce bacterial presence in the test samples by approximately 10-fold over a 2 day period. The chemical composition of these extracts was analysed with High Performance Liquid Chromatography. This showed that there were more compounds present in the ethanol extractions, of which a phenolic compound was the most predominant. The mechanisms by which pine disinfects are complex. There may be a physical effect where bacteria are absorbed in the wood. The antibacterial property is also due to the defensive mechanisms of the plant, which are provided by the combination of chemicals found in resins. Materials can be used to reduce transmission risks, for example by using untreated pine for work surfaces. However, door handles pose a particular problem due to the frequency with which they are touched. The only way to quickly remove bacteria from a door handles is through repeated cleaning. A prototype door handle was built that dispenses a small quantity of disinfectant each time it is used. This was well received by a sample of users. This work has been derived from a school environment, but is relevant for other public buildings such as hospitals, and care homes.