State-of-the-art methods for detection and visualization of bio films on medical devices
In vivo detection of biofilms on medical devices is not currently possible. Approaches to accomplish this could be contraindicated for the patient and would need clinically approved protocols. Therefore, diagnosis of bacterial attachment on medical devices is achieved either by using models or discarded/removed implants, which is not an efficient method to inform clinicians of the appropriate antimicrobial treatments for affected patients (Paredes et al., 2014; Xi, 2014).
Improved bio film imaging
Techniques, such as magnetic resonance imaging (MRI) and optical coherence tomography (OCT), have been used for real-time visualization of the tridimensional structure of biofilms (Xi et al., 2006; Xi, 2014). OCT is a novel medical imaging system that works similarly to ultrasound but yields images with better resolution (10- to 100-fold compared to ultrasound) due to increased penetrability of the near-infrared light that is used by the system. OCT was used in an in vitro model of Pseudomonas aeruginosa biofilms formed in a capillary flow cell providing better images than those obtained with confocal laser scanning electron microscopy (Xi et al., 2006).
Another interesting approach is the detection of biofilms using a combination of high-frequency acoustic microscopy and targeted lipid vesicles (Anastasiadis et al., 2014). This method is based on the fact that biofilms are comprised of 90% matrix and only 10% bacterial cells. In a study by Anastasiadis et al. (2014), encapsulated gas bubbles were conjugated with tetramethylrhodamine isothiocyanate- streptavidine (red stain) and detected on the surface of an Staphylococcus aureus matrix previously labeled with fluorescent green stain. The gas bubbles bound to the matrix scattered sound and produced an acoustic signal that was measured using high-frequency scanning acoustic microscopy. Detection of the bubbles provides a futuristic approach for noninvasive in vivo diagnosis of biofilm matrix at the early stages of formation.
Efforts have also been made to increase the processing of biofilm images taken with advanced technologies such as X-ray microtomography. The development of new software is key to efficiently characterize the structure of biofilms. A new interactive software, BiofilmViewer, has been developed which can transfer data to existing visualization techniques enhancing the resolution of biofilm images (Thomas et al., 2014).