Staphylococcus aureus and Escherichia coli dual-species biofilms on nanohydroxyapatite loaded with CHX or ZnO nanoparticles.

Implant-associated infections are caused by surface-adhering microorganisms persisting as biofilms, resistant to host defense and antimicrobial agents. Given the limited efficacy of traditional antibiotics, novel strategies may rely on the prevention of such infections through the design of new biomaterials. In this work, two antimicrobial agents applied to nanohydroxyapatite materials-namely, chlorhexidine digluconate (CHX) and zinc oxide (ZnO) nanoparticles-were compared concerning their ability to avoid single- or dual-species biofilms of Staphylococcus aureus and Escherichia coli. The resulting biofilms were quantified by the enumeration of colony-forming units and examined by confocal microscopy using both Live/Dead staining and bacterial-specific fluorescent in situ hybridization. The sessile population arrangement was also observed by scanning electron microscopy. Both biomaterials showed to be effective in impairing bacterial adhesion and proliferation for either single- or dual-species biofilms. Furthermore, a competitive interaction was observed for dual-species biofilms wherein E. coli exhibited higher proliferative capacity than S. aureus, an inverse behavior from the one observed in single-species biofilms. Therefore, either nanoHA-CHX or nanoHA-ZnO surfaces appear as promising alternatives to antibiotics for the prevention of devices-related infections avoiding the critical risk of antibiotic-resistant strains emergence. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 491-497, 2017.

A modular reactor to simulate biofilm development in orthopedic materials

Surfaces of medical implants are generally designed to encourage soft- and/or hard-tissue adherence, eventuallyleading to tissue- or osseo-integration. Unfortunately, this feature may also encourage bacterial adhesion and biofilm formation.To understand the mechanisms of bone tissue infection associated with contaminated biomaterials, a detailed understanding ofbacterial adhesion and subsequent biofilm formation on biomaterial surfaces is needed. In this study, a continuous-flow modularreactor composed of several modular units placed in parallel was designed to evaluate the activity of circulating bacterialsuspensions and thus their predilection for biofilm formation during 72 h of incubation. Hydroxyapatite discs were placed ineach modular unit and then removed at fixed times to quantify biofilm accumulation. Biofilm formation on each replicate ofmaterial, unchanged in structure, morphology, or cell density, was reproducibly observed. The modular reactor therefore provedto be a useful tool for following mature biofilm formation on different surfaces and under conditions similar to those prevailingnear human-bone implants (AU)

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A modular reactor to simulate biofilm development in orthopedic materials.

Surfaces of medical implants are generally designed to encourage soft- and/or hard-tissue adherence, eventually leading to tissue- or osseo-integration. Unfortunately, this feature may also encourage bacterial adhesion and biofilm formation. To understand the mechanisms of bone tissue infection associated with contaminated biomaterials, a detailed understanding of bacterial adhesion and subsequent biofilm formation on biomaterial surfaces is needed. In this study, a continuous-flow modular reactor composed of several modular units placed in parallel was designed to evaluate the activity of circulating bacterial suspensions and thus their predilection for biofilm formation during 72 h of incubation. Hydroxyapatite discs were placed in each modular unit and then removed at fixed times to quantify biofilm accumulation. Biofilm formation on each replicate of material, unchanged in structure, morphology, or cell density, was reproducibly observed. The modular reactor therefore proved to be a useful tool for following mature biofilm formation on different surfaces and under conditions similar to those prevailing near human-bone implants.