It is well known that we play host to an extraordinarily large amount of bacteria - in fact people have more bacterial cells in and on our bodies than we have human cells1. And no man is an island: these bacteria are constantly being transferred to our environment, either by direct human contact or by emission from our breath, skin, hair and clothes. Humans shed around one million particles per hour, many of these containing bacteria. Previous studies have shown that people can leave behind bacterial signatures on surfaces that they have touched and in some cases, these bacterial signatures can even be traced back to an individual person2.