Unveiling the fate of adhering bacteria to antimicrobial surfaces: expression of resistance-associated genes and macrophage-mediated phagocytosis

Abstract

Since most antibacterial coatings reported to fight biomaterial-associated infections (BAI) fail in completely preventing bacterial colonization, it is crucial to know the impact of that small fraction of adhered bacteria in BAI recrudescence. This study aims to understand the fate of Staphylococcus aureus able to adhere to an antimicrobial coating previously developed, in terms of potential development of bacterial resistance and their macrophage-mediated phagocytosis. Antimicrobial coating comprised the co-immobilization of Palm peptide and DNase I onto polydimethylsiloxane. Expression of genes associated to resistance and virulence mechanisms showed that cells in contact with antimicrobial surfaces for a long period of 30 days, exhibit genes equally or less expressed, as compared to cells recovered from control surfaces. Recovered cells also exhibit the same susceptibility patterns, which strengthens the evidence of no resistance development. Remarkably, cells adhered to modified surfaces shows a reduced metabolic activity upon vancomycin treatment unlike the cells found on control surfaces, which can be identified as a clinical opportunity for prophylactically administration after implant surgery. Furthermore, results highlight that functionalization of PDMS with Palm and DNase I should not compromise the action of host immune cells. The overall results reinforce the potential of this antimicrobial strategy to fight BAI.

Tailoring the immobilization and release of chlorhexidine using dopamine chemistry to fight infections associated to orthopedic devices

“…Results showed that these cells exhibited a similar susceptibility pattern as the cells recovered from the control surfaces with no CHX (SS and pDA), thus suggesting no development of resistance in these conditions. These results corroborate the theory that compounds immobilization decreases their propensity to induce bacterial resistance [52,53]. It should also be mentioned that the probable very low amount of CHX still remaining on these surfaces can also contribute for this absence of resistance development.…”

“…The Staphylococci strains used in this study also exhibited an in vitro adaption to sub-inhibitory concentrations of CHX in solution, which strengthen these concerns. CHX immobilization can offer an advantage, as it has been showed that immobilized antimicrobial compounds show less propensity for developing bacterial resistance [52]. However, for antimicrobial releasing strategies, such as the ones presented in this study, a scenery in which the agent reaches sub-inhibitory concentrations after its release can present a problem.…”

An Amphiphilic Carbonaceous/Nanosilver Composite-Incorporated Urinary Catheter for Long-Term Combating Bacteria and Biofilms

“…Encouraged by these results, we next incorporated ACPs@AgNPs into silicone rubber to prepare a simple urinary catheter (UC/ACPs@AgNPs) by using a laboratory-made mold. Silicone rubber was selected given its excellent biocompatibility, good mechanical properties, and broad application as a urinary catheter material. , As depicted in Figure a,c, no obvious phase separation was observed between ACPs@AgNPs and silicone rubber, indicating that ACPs@AgNPs were capable of being dispersed into hydrophobic silicone rubber. Urinary catheters suffer from body actions after their transplantation in vivo ; hence, their mechanical integrity should be evaluated after the incorporation of ACPs@AgNPs.…”

Immobilised teicoplanin does not demonstrate antimicrobial activity against Staphylococcus aureus

“…In doing so the selected agent is firmly fixed to the implant surface thereby securing increased residence time and reducing the risk of antimicrobial leaching into the surrounding environment. Immobilised antimicrobials must therefore act at the level of the cell wall and/or membrane 2 and display evidence of functionality when tethered to a surface. One such candidate is Teic, a macrocyclic glycopeptide antibiotic, which has found widespread use as a chiral selector in enantiomeric chromatography 3 – 9 , 12 , 13 and attacks Gram-positive bacteria at the level of the cell wall 10 .…”

“…Minimising infection risk of implantable bone biomaterials, e.g., titanium (Ti), continues to be a priority area in contemporary materials science research 1 . Covalent grafting of suitable antibacterial agents to Ti could be a potential route but finding solutions to creating antibacterial surfaces is especially challenging; selected agents need to retain functionality when in a stationary, immobile state and need to demonstrate biocidal activity by acting at the level of the cell wall or membrane 2 . Evidence of stability to γ-irradiation typically applied to medical devices is also highly desirable.…”