Biofilms associated with invasive devices
Transient use medical devices
Pathogen adhesion has become a significant problem in the use of transient medical devices, which usually are either disposable or reusable after sterilization. It is of crucial importance to understand the biofilms’ development mechanism on the surface of transient reusable devices and the means of their annihilation since they are often employed for more than one patient (Garrett et al., 2008).
Murdoch et al. developed a study to evaluate the contamination degree of various surgical instruments by measuring the concentration of specific proteins found on their surface. The instruments, varying from retractors, scissors, forceps, gags, dissectors, sponge and needle holders, specimen bottles, and other metal tubes and clips, were studied before and after being subjected to commonly employed sterilization methods for comparative evaluation. Their paper highlighted the fact that even though decontamination procedures drastically decrease the viability of the pathogens, they are not 100% effective. Detergents, mostly, were found to fail meeting the 99.9% reduction in bacterial load criteria. Moreover, the rinse water was found to be septic, favoring the formation of P. aeruginosa biofilms (Murdoch et al., 2006).
Studying the contamination of indispensable devices, such as catheters, has been an ongoing process. Immobilized microbe colonies on the surface of tubes used for drainage or drug administration can lead to severe infections, most often related to bloodstream and urinary tract infections. For preventing the biofilms, several strategies have been designed, from surface modification to antimicrobial nanoparticles doping and antiquorum-sensing drugs administration (Boucherit-Atmani et al., 2011; Ren et al., 2015).
A recent paper, published in 2015, subjected the idea of a new strategy meant to inhibit the development of bacterial infections on implantable medical devices. First, they modeled a catheter headed with a copper wire electrode and a nitrite salt solution reservoir meant to electrochemically release nitric oxide. This biomimetic approach was inspired by the endothelial cells, which produce nitric oxide to prevent adhesion and aggregation of both self (platelets) and non-self-entities (pathogens). The in vitro studies made on S. aureus and E. coli revealed bacterial counts lowered by up to 99.9% on such improved surfaces (Ren et al., 2015). Another approach to reduce the formation of biofilms on the surface of catheter tubes was employed in order to reduce the development of planktonic C. albicans. In this study a nanoscale model of a polyelectrolyte multilayers (PEMs) loaded with p-peptides with antifungal activity was utilized. It was demonstrated that coating catheter tubes with nanostructures containing polyglycolic acid and poly-L-lysine PEMs can have a strong antifungal effect (Raman et al., 2014).
S. aureus and P. aeruginosa are common biofilm-forming species on the surface of transient tubes. Banerjee et al. investigated the effect of a novel antibacterial agent, Next-Science (NS), on the inner and outer surfaces of tympastonomy tubes. The test revealed that NS had the ability to annihilate bacterial agents by destabilizing membrane proteins and causing cell lysis, at various concentrations. Moreover, a chelation of calcium was also observed, which determined a matrix destabilization and, thus, a biofilm- inhibiting effect (Banerjee et al., 2015).
Commonly, endoscope-contaminating species, such as P. aeruginosa, S. aureus, or Mycobacterium abscessus subsp. bolletii, were subjected to various tests in order to determine the effect on disinfection assays and procedures toward their biofilm development. Parameters such as the time after clinical use and the various times of procedure employment were factored in. The study concluded that commonly recommended protocols are efficient enough if thoroughly carried out, and a classification of assays and antimicrobial agent widely used was also made. However, despite the success of the sterilization methods, a key aspect in reducing biofilm development is prevention (Neves et al., 2015).
Due to the aggressive nature of biofilm infections related to medical instruments, especially the ones which come in contact with extended areas of tissues (mostly epithelium and endothelium), the studies meant to improve the design and antibiofilm characteristics of such devices are still challenging and restless. As a novelty, a group of scientist came up with an outstanding and yet simple system—active surface deformation—meant to detach the biofilm from silicon substrates. The urinary catheter proposed by the group of researchers is provided with a multiinflation-lumen that can detach biofilms in inaccessible areas. Even though still in the prototype phase, the performance characterization for E. coli and Proteus mirabilis biofilms reduction is promising. Furthermore, deformation of the surface can be easily controlled on demand and repeatedly, with similar results (Levering et al., 2016).