# Novel Approaches to Combat Medical Device-Associated BioFilms
## 2 Medical Device-Related Biofilm Infection and the Challenges of Treatment  
Implantable medical devices have become an integral part of treatments in clinical work. However, in the body, external implantation is often accompanied by infection complications. Approximately 60%-70% of nosocomial infections are associated with bio-materials or implants [24]. Medical device-related biofilm infections are mainly caused by the colonization of microorganisms on abiotic surfaces, such as indwelling medical devices. All implantable medical devices (e.g., cardiac pacemakers, artificial heart valves, hemodialysis, artificial joints, needleless connectors, center venous catheters, urinary catheters, endotracheal intubation, artificial breasts, contact lenses, and orthodontal prosthetics) carry the risk of biofilm-related infections, which severely affect the quality of life and even endanger life. We have tried to summarize the rates of infection for some of the most common medical devices (Table 1). Catheter-related urinary tract infections are very common, and microorganisms in biofilms on the inner surface of the catheter in patients with long-term catheterization can resist antibiotic treatment and cause chronic infections [25]. Biofilms formed by microorganisms in the endotracheal tube are related to ventilator-associated pneumonia, which is one of the most common infections in the intensive care unit (ICU) and the main cause of death [26]. Long-term medical implants can cause inflammation and tissue destruction around implants, and sometimes, these infections are life threatening [1]. Pathogens contaminate indwelling medical devices through a variety of exogenous pathways. Foreign microorganisms can be transferred to the surface of medical devices, either through cross-infection of the surgical devices, direct inoculation during device placement, or migration of the surrounding skin mucosal sheath [1]. Host-related bacteria can colonize the implanted device after the operation, such as bacteria from the respiratory tract, urinary tract, and gastrointestinal tract [25]. In addition, microorganisms can form a medical device-associated biofilm through a bloodstream infection. Irrespective of whether the microbes that cause infection are present inside or outside the body, medical device-related infections often begin with the colonization of bacteria on the surface of the device and go through a series of complex changes leading to the formation of biofilms. Persistent biofilms are the main cause of chronic wound infection and infection recurrence. In a meta-analysis study, the prevalence of biofilms in chronic wound infections was 78.2% [27]. Biofilms formed on chronic peritoneal dialysis catheters are considered to be an important cause of peritonitis recurrence or persistence [28]. Biofilm-associated infections are often exacerbated by the host's strong proinflammatory response to persistent microbial stimulation, which may greatly promote tissue damage [10]. Microbial cells may separate from the biofilm and spread to surrounding tissues or blood, thereby further worsening the clinical outcome of the infection [29]. Various pathogens have been implicated in device-related infections. Some pathogens that form biofilms originate from the skin and contaminate the device during implantation or insertion. _Staphylococcus epidermidis, Staphylococcus aureus,_ and _Candidia albicans_ are common microbes on the skin; therefore, they are the most important pathogenic cause of implant biofilm infections [1, 30, 31, 32]. However, the pathogens that form biofilms are different at different sites of infection and are related to many factors. For example, the most common pathogen in biofilms formed on indwelling catheters is _Escherichia coli_, and the sex, catheterization period, and catheter type have also been shown to be significantly correlated with catheter biofilms [33]. Several microorganisms of the normal flora cause infection when the immune system is compromised, including _E.