These data demonstrate the clinical potential of covalently bound VAN and CAS on Ti to reduce microbial biofilm formation without jeopardizing osseointegration.

Nosocomial and community-acquired infections caused by multidrug resistant bacteria represent a major human health problem. Thus, there is an urgent need for the development of antibiotics with new modes of action. In this study, we investigated the antibacterial characteristics and mode of action of a new antimicrobial compound, SPI031 (N-alkylated 3, 6-dihalogenocarbazol 1-(sec-butylamino)-3-(3,6-dichloro-9H-carbazol-9-yl)propan-2-ol), which was previously identified in our group. This compound exhibits broad-spectrum antibacterial activity, including activity against the human pathogens Staphylococcus aureus and Pseudomonas aeruginosa. We found that SPI031 has rapid bactericidal activity (7-log reduction within 30 min at 4x MIC) and that the frequency of resistance development against SPI031 is low. To elucidate the mode of action of SPI031, we performed a macromolecular synthesis assay, which showed that SPI031 causes non-specific inhibition of macromolecular biosynthesis pathways. Liposome leakage and membrane permeability studies revealed that SPI031 rapidly exerts membrane damage, which is likely the primary cause of its antibacterial activity. These findings were supported by a mutational analysis of SPI031-resistant mutants, a transcriptome analysis and the identification of transposon mutants with altered sensitivity to the compound. In conclusion, our results show that SPI031 exerts its antimicrobial activity by causing membrane damage, making it an interesting starting point for the development of new antibacterial therapies.

In nature, bacteria predominantly reside in structured, surface-attached communities embedded in a self-produced, extracellular matrix. These so-called biofilms play an important role in the development and pathogenesis of many infections, as they are difficult to eradicate due to their resistance to antimicrobials and host defense mechanisms. This review focusses on the biofilm-forming periodontal bacterium Porphyromonas gingivalis. Current knowledge on the virulence mechanisms underlying P. gingivalis biofilm formation is presented. In addition, oral infectious diseases in which P. gingivalis plays a key role are described, and an overview of conventional and new therapies for combating P. gingivalis biofilms is given. More insight into this intriguing pathogen might direct the development of better strategies to combat oral infections.

Roughened surfaces are increasingly being used for dental implant applications as the enlarged contact area improves bone cell anchorage, thereby facilitating osseointegration. However, the additional surface area also entails a higher risk for the development of biofilm associated infections, an etiologic factor for many dental ailments, including peri-implantitis. To overcome this problem, we designed a dental implant composed of a porous titaniumsilica (Ti/SiO 2 ) composite material and containing an internal reservoir that can be loaded with antimicrobial compounds. The composite material consists of a sol-gel derived mesoporous SiO 2 diffusion barrier integrated in a macroporous Ti load-bearing structure obtained by powder metallurgical processing. The antimicrobial compounds can diffuse through the porous implant walls, thereby reducing microbial biofilm formation on the implant surface. A continuous release of µM concentrations of chlorhexidine through the Ti/SiO 2 composite material was measured, without initial burst effect, over at least 10 days and using a 5 mM chlorhexidine solution in the implant reservoir. Metabolic staining, CFU counting and visualisation by scanning electron microscopy confirmed that Streptococcus mutans biofilm formation on the implant surface was almost completely prevented due to chlorhexidine release (preventive setup). Moreover, we demonstrated efficacy of released chlorhexidine against mature Streptococcus mutans biofilms (curative setup). In conclusion, we provide a proof of concept of the sustained release of chlorhexidine, one of the most widely used oral antiseptics, through the Ti/SiO 2 material thereby preventing and eradicating biofilm formation on the surface of the dental implant. In principle, our flexible design allows for the use of any bioactive compound, as discussed.

Biofilm-associated infections, particularly those caused by Staphylococcus aureus, are a major cause of implant failure. Covalent coupling of broad-spectrum antimicrobials to implants is a promising approach to reduce the risk of infections. In this study, we developed titanium substrates on which the recently discovered antibacterial agent SPI031, a N-alkylated 3, 6-dihalogenocarbazol 1-(sec-butylamino)-3-(3,6-dichloro-9H-carbazol-9-yl)propan-2-ol, was covalently linked (SPI031-Ti). We found that SPI031-Ti substrates prevent biofilm formation of S. aureus and Pseudomonas aeruginosa in vitro, as quantified by plate counting and fluorescence microscopy. To test the effectiveness of SPI031-Ti substrates in vivo, we used an adapted in vivo biomaterial-associated infection model in mice in which SPI031-Ti substrates were implanted subcutaneously and subsequently inoculated with S. aureus. Using this model, we found a significant reduction in biofilm formation (up to 98%) on SPI031-Ti substrates compared to control substrates. Finally, we demonstrated that the functionalization of the titanium surfaces with SPI031 did not influence the adhesion and proliferation of human cells important for osseointegration and bone repair. In conclusion, these data demonstrate the clinical potential of SPI031 to be used as an antibacterial coating for implants, thereby reducing the incidence of implant-associated infections. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2191-2198, 2016.

Oral infections are among the most common diseases worldwide. Many protocols for the prevention and treatment of oral infections have been described, yet no golden standard has been developed so far. The antiseptic chlorhexidine and antibiotics are often used in these treatment procedures. However, long-term use of chlorhexidine can lead to side effects and extensive use of antibiotics can promote the development of antibiotic-resistant bacteria, which in turn can compromise the effectiveness of the treatment. Consequently, it remains important to search for new antibacterial agents for the treatment of oral infections. In this study, we report on the antibacterial activity of the antiasthma drug zafirlukast against oral pathogens Porphyromonas gingivalis and Streptococcus mutans. Furthermore, its activity against oral biofilms grown on titanium surfaces was confirmed. In addition, we demonstrated that zafirlukast displays no cytotoxicity against human osteoblasts. Combined, this study paves the way for further research to determine the potential of zafirlukast to be used as a new antibiotic against oral pathogens.

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The spread of antibiotic resistance and the challenges associated with antiseptics such as chlorhexidine have necessitated a search for new antibacterial agents against oral bacterial pathogens. As a result of failing traditional approaches, drug repurposing has emerged as a novel paradigm to find new antibacterial agents. In this study, we examined the effects of the FDA-approved anticancer agent toremifene against the oral bacteria Porphyromonas gingivalis and Streptococcus mutans. We found that the drug was able to inhibit the growth of both pathogens, as well as prevent biofilm formation, at concentrations ranging from 12.5 to 25 M. Moreover, toremifene was shown to eradicate preformed biofilms at concentrations ranging from 25 to 50 M. In addition, we found that toremifene prevents P. gingivalis and S. mutans biofilm formation on titanium surfaces. A time-kill study indicated that toremifene is bactericidal against S. mutans. Macromolecular synthesis assays revealed that treatment with toremifene does not cause preferential inhibition of DNA, RNA, or protein synthesis pathways, indicating membrane-damaging activity. Biophysical studies using fluorescent probes and fluorescence microscopy further confirmed the membrane-damaging mode of action. Taken together, our results suggest that the anticancer agent toremifene is a suitable candidate for further investigation for the development of new treatment strategies for oral bacterial infections.