Biofilms in Health and the Human Body

This may come as something of a shock to you, but about 90 percent of the cells in a human body are not human! In fact, the human body is heavily colonized by microbes that have found it a great place to live. We have communities of microbes living on all mucous surfaces and in our digestive tract, as well as on and in layers of our skin. For the most part we all get along; in fact, we depend on some of our gut microbes to help with digestion. Sometimes, however, the microbial load causes problems of infection. Dentists now understand, for instance, that dental caries (cavities) are the result of bacterial infection (and biofilms!). When the normal balance of microbial populations is upset or when our immune system is overwhelmed, we can have a real battle with microbial opportunists.

In the 1990s, as the biofilm concept was being introduced to the medical community, doctors began to make the connection between chronic, low-grade infections and the biofilm mode of growth. Dental professionals made the connection easily, as teeth could readily be scraped for microscopic examination. Internal cases of chronic infection have taken longer to prove, but testing has shown that many troublesome diseases have entrenched microbial populations at their core. Peptic ulcers, once thought to be caused by stress, have been proved to be caused by bacterial communities of Helicobacter pylori. The cyclical flare-up and subsidence of otitis media—the most common cause of children's recurrent earaches—is an example of a typical biofilm-based infection. Click to see Table 1-2, a summary of biofilms in medical contexts, the associated impacts, and journal references.