The consequences and prevention of bacterial biofilm infection of silicone breast implants

Bacteria are one of the most successful organisms on the Earth’s surface. Mankind has evolved to utilise many of the actions of bacteria to our benefit and advantage, such as synergistic bacterial colonisation of the gut and its function in digestion. Bacteria also cause many human diseases. Indeed one of the most important human advances over the past 200 years has been the rapid development of the Discipline of Microbiology as it has given medicine the knowledge and ability to now treat and cure many of these previously life-threatening infections. The discovery of bacteria living within communal structures, or biofilms, in the 1970’s challenged much of our scientific and medical knowledge of bacteria in health and disease. Bacterial biofilms are now acknowledged to be important in the aetiology of many infections, including infections of surgical implants. Biofilm infection is estimated to occur in between 1-9% of all surgical implants, depending on the device. These infections are characterised by a chronic indolent inflammatory process that can be punctuated by localised or embolic septic events. They are very difficult to diagnose and treat, commonly requiring surgical removal with or without implant replacement and are associated with rapidly increasing health care costs that are not sustainable into the future. Silicone breast implants are just one type of surgical implant where bacterial biofilm infection has been implicated in a chronic fibrotic inflammation of the implant capsule. There is now increasing evidence that this may lead to capsular contracture, the most common long-term complication of silicone breast implants. This thesis reviews the evidence for the role of bacterial biofilm infection of breast implants and the formation of capsular contracture. It also uses the porcine model of biofilm infection of silicone implants to: 1) further investigate the role of endogenous breast bacteria in the development of capsular contracture; 2) evaluate the ability of a novel antibiotic prosthetic cover to prevent bacterial biofilm infection; 3) investigate the cellular immune response to biofilm infection of silicone implants; and 4) postulate whether biofilm-related chronic inflammation and its immune response may be implicated in the neoplastic process of the new entity of breast implant-associated anaplastic large cell lymphoma.