## 2 Characterization of Bacterial Biofilms
### Alternative Strategies for Combating Bacterial biofilms
Additionally, they can be successfully applied as a device-coating strategy and in combination with antibiotics. Importantly, in contrast to antibiotics, mAbs do not cause resistance development among bacteria, present a high safety level, and have few off-target effects [89]. Another strategy that has gained increasing attention in the treatment of bacterial biofilm-associated infections is antimicrobial photodynamic therapy (PDT). This promising approach, based on the delivery of light-activated photosensitizers (PSs) that generate cytotoxic species, such as ROS (reactive oxygen species), has been reported by different authors. Quite recently, [PERSON] and collaborators showed photodaterial activity of sulfobutyric-\(\beta\)-cyclodextrintrin/cationic porphyrin _meso_-tetra(4-N-methylpyridyl)porphine (TMPyP) nanoassemblies against _P. aeruginosa_, _E. coli_, and _S. aureus_, pathogens frequently involved in biofilm-related infections [92]. In turn, [PERSON] and collaborators developed a synergistic photothermal (PTT)/photodynamic (PDT) therapy strategy for combating the biofilm formed by _S. aureus_ on a titanium implant [93]. Interestingly, the superiority of this combined PTT/PDT strategy over PTT alone is related to the temperature, which is lower, thus enhancing the antibacterial effect [94]. On the other hand, the important advantage of using PDT alone or in the combination strategy is the lack of resistant mutants which may occur in other approaches, including antibiotic therapy. The use of the above-described strategies depends on whether they are intended to prevent or treat nosocomial infections. It is also important to assess whether the biofilm is associated with medical devices or formed on native host tissues. In addition to infections associated with insertion of implants, prostheses, tubes, catheters, and other devices, biofilms are involved in causing endocarditis, urinary tract infections, sinusitis, colitis, dental plaques, gingivitis, and chronic wound infections [29; 95; 96]. Unfortunately, not all of the described strategies can be used to treat infections associated with the formation of biofilm in the patient's body. For example, disinfection or surface-coating techniques are used to prevent medical device-associated infections, but not to treat them. The use of antibiotics is an alternative, although they must be administered at very high concentrations and over a long period of time. Unfortunately, antibiotics and other conventional strategies have limited activity against persisters. Sometimes, surgical removal of the source of biofilm is the only effective solution. As indicated above, it was proposed to use bacteriophages to treat biofilm infections. Several preclinical animal studies supporting the application of phages in these kinds of infections were described and analyzed by [PERSON] in a recent review paper [88]. Importantly, the synergistic activity of phages with antibiotics is also observed. Recently, the quality of phage preparations, their titer and dosage, their routes of administration (local or intravenous), and their safety and interactions with eukaryotic cells have been evaluated and widely discussed in the literature [88; 97]. In contrast to the treatment based on the use of whole viral particles, the application of phage-derived depolymerases may overcome these difficulties. Thus, their use against bacterial biofilms is broadly considered below.