## 6 Biofilms and Healthcare-Associated Infections
### Medical Device Infections  
Developing bacterial biofilms on implantable medical devices presents a significant challenge in contemporary healthcare, greatly influencing device-related infections. Biofilms can form on various medical devices such as catheters, sutures, orthopedic implants, heart valves, and vascular grafts, significantly contributing to HAIs [192; 193; 15]. Upon establishment, biofilms provide a protective environment for bacterial communities by surrounding them with EPS matrix. This matrix improves adhesion to device surfaces and protects bacteria from immune defenses, making biofilm-associated infections particularly resistant to standard treatments [194; 195].  
Infections linked to biofilms present significant clinical challenges, leading to consequences that go beyond localized areas and can result in systemic, potentially life-threatening conditions. For example, biofilms on medical devices are associated with bloodstream infections stemming from central venous catheters, prosthetic joint infections, and infective endocarditis affecting heart valves. The recurrent nature of these infections can be attributed to the protective characteristics of the biofilm, allowing bacterial cells to persist in a dormant state, thereby evading immune detection and standard antimicrobial treatments. In severe instances, infections associated with biofilms can advance to sepsis--a widespread inflammatory reaction that carries a considerable mortality risk if not addressed swiftly [196; 197; 198].  
Eliminating infections linked to biofilms presents significant challenges because of the natural resistance mechanisms present within biofilm structures. The EPS matrix obstructs the penetration of antibiotics while simultaneously prompting a phenotypic shift in bacterial cells, thereby diminishing their vulnerability to conventional treatments. Inactive bacterial cells embedded in the biofilm can endure extended antibiotic treatments, frequently resulting in device removal and replacement being the sole feasible treatment alternative [194; 195].  
The economic cost of biofilm-associated infections is substantial, placing a significant financial strain on global healthcare systems. Central venous catheter-related infections, heavily influenced by biofilm formation, are estimated to cost USD 11.5 billion globally. Similarly, catheter-associated urinary tract infections, affecting approximately 150 million individuals annually, contribute an additional USD 1 billion in healthcare expenses worldwide. These figures highlight the economic burden of managing biofilm-associated complications in catheter use [199].  
Prosthetic joint infections represent another costly challenge driven by biofilm formation. The presence of biofilms on prosthetic surfaces often leads to antibiotic treatment failure, leaving surgery as one of the few viable options. Revision surgeries required to address biofilm-associated prosthetic joint infections contribute a staggering USD 7849 million annually to the global healthcare burden [199; 200].  
Biosensors provide an advanced solution for the early detection of biofilm formation on medical devices, including catheters, implants, and prosthetic joints. These diagnostic instruments may identify biofilm formation in its first phases, often before the manifestation of obvious infection indicators. Integrated with devices, biosensors use technologies such as electrochemical and piezoelectric transducers to detect changes in electrical signals or mass, signifying the existence of biofilms [201; 202]. These sensors exhibit heightenedsensitivity to biofilm-specific indicators, such as QS molecules and microbial metabolites, facilitating accurate and timely detection [203; 204].