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Staphylococcus epidermis has emerged as the main causative agent of medical device-related infections. Their major pathogenicity factor lies in its ability to adhere to surfaces and proliferate into biofilms, which increase their resistance to antibiotics. The main objective of this study was to evaluate the use and the mechanism of action of an ethanolic extract of Spanish propolis (EESP) as a potential alternative for preventing biofilm-related infections caused by S. epidermidis. The chemical composition of propolis is reported and its antibacterial activity against several strains of S. epidermidis with different biofilm-forming capacities evaluated. The influence of sub-inhibitory concentrations (sub-MICs) of EESP on their growth, physicochemical surface properties, adherence, and biofilm formation were studied. EESP interferes with planktonic cells, homogenizing their physicochemical surface properties and introducing a significant delay in their growth. The adherence and biofilms at the EESP concentrations investigated were decreased up to 90.5% among the strains. Microscopic analysis indicated that the planktonic cells that survived the treatment were the ones that adhere and proliferate on the surfaces. The results obtained suggest that the EESP has a high potential to be used as an inhibitor of both the adhesion and biofilm formation of S. epidermidis. [ABSTRACT FROM AUTHOR]

Inthis study, the structure and mechanical stability of humanplasma fibronectin (HFN), a major protein component of blood plasma,have been evaluated in detail upon adsorption on the nonirradiatedand irradiated Ti6Al4V materialthrough the use of atomic force microscopy. The results indicatedthat the material surface changes occurring after the irradiationprocess reduce the disulfide bonds that typically preclude the mechanicaldenaturation of individual HFN domains and interfere significantlywith the intraionic interactions stabilizing the compact conformationof the adsorbed HFN molecules. In particular, upon adsorption on thismaterial, the molecules adopt a more flexible conformation and becomemechanically more compliant. Unexpected observations also indicatedthat, regardless the material surface, a single HFN molecule can bepulled into an extended conformation without the unfolding of itsdomains through a series of three unraveling steps. The forces involvedin the unraveling process were found to be generally lower than theforces required to unfold the individual protein domains. This reportis the first one to present the force displacement details associatedto the straightening of a single compact protein at the molecularlevel. [ABSTRACT FROM AUTHOR]

Biomaterial implant-associated infections, a common cause of medical devices' failure, are initiated by bacterial adhesion to an adsorbed protein layer on the implant material surface. In this study, the influence of protein surface orientation on bacterial adhesion has been examined using three clinically relevant bacterial strains known to express specific binding sites for human plasma fibronectin (HFN). HFN was allowed to adsorb on hydrophobic Ti6Al4V and physically modified hydrophilic Ti6Al4V substrata. Ellipsometric data reveal that the characteristics of the adsorbed protein layers primary depend on solid surface tension and the initial protein concentration in solution. In particular, HFN molecules adopt a more extended conformation on hydrophobic than hydrophilic surfaces, an effect that is more pronounced at low than at high initial protein concentrations. Moreover, the extended conformation of the protein molecules on these surfaces likely facilitates the exposure of specific sites for adhesion, resulting in the higher bacterial-cell attachment observed regardless of the strain considered. Contact angle measurements and the analysis of the number of remaining adhering cells after being subjected to external forces further suggest that both specific and nonspecific (hydrophobic) interactions play an important role on bacterial attachment. This study is the first one to evaluate the influence of surface hydrophobicity on protein adsorption and its subsequent effect on bacterial adhesion using a material whose hydrophobicity was not modified using chemical treatments that potentially led to surface properties changes other than hydrophobicity. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. [ABSTRACT FROM AUTHOR]

In this paper, a simple numerical procedure is presented to monitor the growth of Streptococcus sanguinis over time in the absence and presence of propolis, a natural antimicrobial. In particular, it is shown that the real-time decomposition of growth curves obtained through optical density measurements into growth rate and acceleration can be a powerful tool to precisely assess a large range of key parameters (i.e., lag time [t0], starting growth rate [g0], initial acceleration of the growth [a0], maximum growth rate [gmax], maximum acceleration [amax], and deceleration [amin] of the growth and the total number of cells at the beginning of the saturation phase [Ns]) that can be readily used to fully describe growth over time. Consequently, the procedure presented provides precise data of the time course of the different growth phases and features, which is expected to be relevant, for instance, to thoroughly evaluate the effect of new antimicrobial agents. It further provides insight into predictive microbiology, likely having important implications for assumptions adopted in mathematical models to predict the progress of bacterial growth. IMPORTANCE The new and simple numerical procedure presented in this paper to analyze bacterial growth will possibly allow the identification of true differences in efficacy among antimicrobial drugs for their applications in human health, food security, and the environment, among others. It further provides insight into predictive microbiology, likely helping in the development of proper mathematical models to predict the course of bacterial growth under diverse circumstances. [ABSTRACT FROM AUTHOR]

In this paper, a simple numerical procedure is presented to monitor the growth of Streptococcus sanguinis over time in the absence and presence of propolis, a natural antimicrobial. In particular, it is shown that the real-time decomposition of growth curves obtained through optical density measurements into growth rate and acceleration can be a powerful tool to precisely assess a large range of key parameters (i.e., lag time [ t 0 ], starting growth rate [γ 0 ], initial acceleration of the growth [ a 0 ], maximum growth rate [γ max ], maximum acceleration [ a max ], and deceleration [ a min ] of the growth and the total number of cells at the beginning of the saturation phase [ N s ]) that can be readily used to fully describe growth over time. Consequently, the procedure presented provides precise data of the time course of the different growth phases and features, which is expected to be relevant, for instance, to thoroughly evaluate the effect of new antimicrobial agents. It further provides insight into predictive microbiology, likely having important implications for assumptions adopted in mathematical models to predict the progress of bacterial growth. IMPORTANCE The new and simple numerical procedure presented in this paper to analyze bacterial growth will possibly allow the identification of true differences in efficacy among antimicrobial drugs for their applications in human health, food security, and the environment, among others. It further provides insight into predictive microbiology, likely helping in the development of proper mathematical models to predict the course of bacterial growth under diverse circumstances.