Biofilms have been found to be involved in a wide variety of infections in the body, by one estimate 80% of all infections. Biofilms form on indwelling medical devices such as catheters, artificial heart valves, prosthetic joints and internal fracture fixation (IFF) devices and often cause severe, chronic infections. Approximately 3% of all patients receiving implants develop biofilm associated infections (BAI). For example, in the UK there are an estimated 86,000 hip fractures annually in the UK and deep infection rates of between 1.3% and 3.6% have been reported. The presence of a deep infection in hip fracture cases resulted in a doubling of operative costs, a tripling of investigation costs and a quadrupling of ward costs. In the US annually approximately 100.000 implanted IFF devices become infected. The associated costs are estimated at $1.5 billion. In the next decades the use of such medical devices will grow considerably mainly because of demographic changes due to an ever increasing elderly population, resulting in an increased number of patients suffering infections with even more increasing antimicrobial resistance.
Biofilms are aggregates of microorganisms in which cells adhere to each other and/or to a surface. These adherent cells are embedded within a self-produced matrix of extracellular substance, often referred to as slime. This is a polymeric matrix generally composed of extracellular polysaccharides, proteins, and DNA in various configurations.
Biofilms have specific characteristics that enable them to withstand the conventional antibiotic therapies. The matrix in which bacteria in biofilms are embedded protects the bacteria from external influences, such as antimicrobial substances. Biofilms are notoriously resistant to antibiotics and even long-term use of high concentrations of antibiotics does not ensure the eradication of the bacteria within biofilms.
As a consequence, the current treatment strategies to prevent or treat biofilms are inadequate. Antibiotic treatment of implant-associated infections is unsuccessful in up to 32 to 82% of the cases and results in chronic infection and inflammation. Failure of the antibiotic treatment of biofilm necessitates surgical removal of the medical device or other serious medical interventions and are associated with substantial morbidity and mortality1. In most cases the tissue around the extracted implant remains infected. Next to the fact that BAI associated extra health care costs are extremely high as discussed above, the negative impact on the quality of life of patients suffering from biofilm related infections is huge. The infections can cause severe pain and impaired mobility. Besides physical complaints, chronic infections can cause depression, social deprivation and decreased economical participation.