Strategies to control Staphylococcus epidermidis biofilms

Staphylococcus epidermidis is the staphylococci species most commonly associated with bacteremia and hospital-acquired infections and has recently arisen as the leading cause of infections related to indwelling medical devices such as vascular catheters, prosthetic joints and artificial heart valves. The prevalence of S. epidermidis in hospital-acquired infections is due to its ability to adhere and form biofilms on biomaterial surfaces. This feature is one of the most important virulence factors found in S. epidermidis. In biofilm form, bacteria are protected from antimicrobial agents and the host immune system contributing to the persistence of biofilm infections. In addition, the emergence of S. epidermidis resistance to conventional therapies, based in the use of traditional antibiotics, leads to the failure of the current treatments used in the combat of S. epidermidis infections and is becoming a major concern. These facts are stimulating the continuous search for novel agents able to eradicate S. epidermidis biofilm infections or that can work in synergy with the currently available antimicrobial agents. New strategies have been showing encouraging in vitro results in controlling S. epidermidis biofilms and seem to be promising alternatives to standard antibiotics usually used in the treatment of S. epidermidis related infections

Farnesol in combination with N-acetylcysteine against staphylococcus epidermidis planktonic and biofilm cells

Staphylococcus epidermidis is the most frequent cause of nosocomial sepsis and catheter-related infections, in which biofilm formation is considered to be the main virulence mechanism. In biofilm environment, microbes exhibit enhanced resistance to antimicrobial agents. This fact boosted the search of possible alternatives to antibiotics. Farnesol and N-acetylcysteine (NAC) are non-antibiotic drugs that have demonstrated antibacterial properties. In this study, the effect of farnesol and NAC isolated or in combination (farnesol+NAC) was evaluated. NAC at 10 × MIC caused a total cell death in planktonic cells. On the other hand, S. epidermidis biofilms exhibited 4 log reduction in viable cell number after a 24h treatment with NAC at the former concentration. Our results demonstrated that there was a higher CFU log reduction of S. epidermidis planktonic cells when farnesol was combined with NAC at 1 × MIC relatively to each agent alone. However, these results were not relevant because NAC alone at 10 × MIC was always the condition which gave the best results, having a very high killing effect on planktonic cells and a significant bactericidal effect on biofilm cells. This study demonstrated that no synergy was observed between farnesol and NAC. However, the pronounced antibacterial effect of NAC against S. epidermidis, on both lifestyles, indicates the use of NAC as a potential therapeutic agent in alternative to antibiotics.Fernanda Gomes and Pilar Teixeira fully acknowledge the financial support of Fundacao para a Ciencia e Tecnologia (FCT) through the grants SFRH/BD/32126/2006 and SFRH/BPD/26803/2006, respectively

Response of Staphylococcus epidermidis biofilms cells to the effect of farnesol

Objective:Staphylococcus epidermidis is a leading cause of medical-device-related infections, especially in immunocompromised patients. The treatment of these infections is further complicated by the emergence of multiresistant strains. The ability of S. epidermidis to form biofilms on biotic and abiotic surfaces is believed to contribute significantly to the pathogenesis of these infections. Biofilms are notoriously difficult to eradicate and are often resistant to systemic antibiotic therapy. Recently, farnesol has been described as having antimicrobial properties, and therefore a possible action on the prevention of S. epidermidis related infections. In previous studies it was shown that 300 microM farnesol was effective against S. epidermidis planktonic cells but having only a slight effect on biofilm cells. So, the goal of this study was to assess the antimicrobial activity of higher farnesol concentrations (1 and 100 mM) against biofilm cells of S. epidermidis. Methods: Two S. epidermidis strains biofilm-producing (9142 and 1457) were used in this study. Farnesol (0, 1 mM, 100 mM) was added to 24 h biofilm cells. Biofilm formation was assessed through crystal violet (CV) staining that measure total biomass of biofilm and cellular viability through XTT and colony-forming units (CFU/ml). Results: The results didn't show a significant effect of both farnesol concentrations on biofilm biomass and activity. In fact, biofilm cell reduction was less than 2 Log, similarly to most antibiotics (e.g. tetracycline and vancomycin). Conclusion: Although the reduction promoted by farnesol was less than 3 Log as requested for an antibiotic agent, its efficacy is similar to vancomycin. On account of that we are now testing the combined effect of farnesol with agents that disrupt the biofilm matrix

Agrobiodiversidade como base para sistemas agrícolas sustentáveis para a agricultura familiar.

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AIOCJ: A Choreographic Framework for Safe Adaptive Distributed Applications

We present AIOCJ, a framework for programming distributed adaptive applications. Applications are programmed using AIOC, a choreographic language suited for expressing patterns of interaction from a global point of view. AIOC allows the programmer to specify which parts of the application can be adapted. Adaptation takes place at runtime by means of rules, which can change during the execution to tackle possibly unforeseen adaptation needs. AIOCJ relies on a solid theory that ensures applications to be deadlock-free by construction also after adaptation. We describe the architecture of AIOCJ, the design of the AIOC language, and an empirical validation of the framework.Comment: Technical Repor