1,721,045 research outputs found
Treatment of microbial biofilms in the post-antibiotic era: Prophylactic and therapeutic use of antimicrobial peptides and their design by bioinformatics tools
Full text linkThe treatment for biofilm infections is particularly challenging because bacteria in these conditions become refractory to antibiotic drugs. The reduced effectiveness of current therapies spurs research for the identification of novel molecules endowed with antimicrobial activities and new mechanisms of antibiofilm action. Antimicrobial peptides (AMPs) have been receiving increasing attention as potential therapeutic agents, because they represent a novel class of antibiotics with a wide spectrum of activity and a low rate in inducing bacterial resistance. Over the past decades, a large number of naturally occurring AMPs have been identified or predicted from various organisms as effector molecules of the innate immune system playing a crucial role in the first line of defense. Recent studies have shown the ability of some AMPs to act against microbial biofilms, in particular during early phases of biofilm development. Here, we provide a review of the antimicrobial peptides tested on biofilms, highlighting their advantages and disadvantages for prophylactic and therapeutic applications. In addition, we describe the strategies and methods for de novo design of potentially active AMPs and discuss how informatics and computational tools may be exploited to improve antibiofilm effectiveness
Development of Effective Antibacterial Treatment: Lessons from the Past and Novel Approaches
Full text linkIn the last three decades, the appearance and rapid diffusion of antibiotic-resistant bacterial strains have been observed [...]
In silico design of antimicrobial peptides
No full textThe rapid spread of drug-resistant pathogenic microbial strains has created an urgent need for the development of new anti-infective molecules, having different mechanism of action in comparison to existing drugs. Natural antimicrobial peptides (AMPs) represent a novel class of molecules with a broad spectrum of activity and a low rate in inducing bacterial resistance. In particular, linear alphahelical cationic antimicrobial peptides are among the most widespread membrane-disruptive AMPs in nature, representing a particularly successful structural arrangement of the innate defense against microbes. However, until now, many AMPs have failed in clinical trials because of several drawbacks that strongly limit their applicability such as degradation, cytotoxicity, and high production cost. Thus, to overcome the limitations of native peptides, a rational in silico approach to AMPs design becomes a promising strategy that drastically reduce production costs and the time required for evaluation of activity and toxicity. This chapter focuses on the strategies and methods for de novo design of potentially active AMPs. In particular, statistical-based design strategies and MD methods for modelling AMPs are elucidated
Synergistic antibiotic activity against planktonic and biofilmembedded Streptococcus agalactiae, Streptococcus pyogenes and Streptococcus oralis
Full text linkObjectives: To determine the antimicrobial activity against streptococcal biofilm in species mostly isolated from implant-associated infections and examine the effect of enzyme treatment of biofilm on the antimicrobial activity of different antibiotics. Methods: The activities of fosfomycin, rifampicin, benzylpenicillin, daptomycin, gentamicin, levofloxacin, proteinase K and their combinations on planktonic and/or biofilm-embedded standard laboratory strains of Streptococcus agalactiae, Streptococcus pyogenes and Streptococcus oralis were investigated in vitro by standard methods and isothermal microcalorimetry. Results: MIC values obtained for the tested antimicrobials against planktonic bacteria ranged from 0.016 to 128 mg/L for the three species tested. Higher antibiotic concentrations were usually required to reduce biofilm in comparison with planktonic bacteria, with the exception of gentamicin, for which similar concentrations (4-16 mg/L) exerted an effect on both planktonic and biofilm cells. A synergistic effect against the streptococcal biofilm of the three species was observed when gentamicin was combined with benzylpenicillin or with rifampicin. Moreover, antibiotic concentrations comparable to the MIC observed against planktonic cells induced a strong reduction of viable bacteria in proteinase K pre-treated biofilm. Conclusions: This study shows that the combination of gentamicin with either benzylpenicillin or rifampicin exerts a synergistic effect against biofilms produced by the tested streptococci strains in vitro. Our results also suggest that coupling a dispersal agent with conventional antibiotics may facilitate their access to the bacteria within the biofilm. In vivo and clinical studies are needed in order to confirm whether such a strategy may be effective in the treatment of implant-associated infections caused by streptococci
Antimicrobial peptides for the control of biofilm formation
No full textAntimicrobial peptides (AMPs) are an abundant and varied group of molecules recognized as the most ancient components of the innate immune system. They are found in a wide group of organisms including bacteria, plants and animals as a defense mechanism against different kinds of infectious pathogens. Over the past two decades, a fast-growing number of AMPs have been identified/designed and their wide-spectrum antimicrobial activity has been deeply investigated. In recent years, there has been an increasing interest in the use of AMPs as alternative anti-biofilm molecules for the control of biofilm-related infections. Biofilms are sessile communities of microbial cells embedded in a self-produced matrix and characterized by a low metabolic activity. Due to their peculiar physiological properties, bacteria/fungi in biofilms result more resistant to conventional antibiotic therapies compared with their planktonic counterparts. AMPs may be a promising strategy to combat biofilm-related infections, as many of them target the microbial membrane, thus being potentially effective also on metabolically inactive cells. Investigations conducted so far evidenced that these peptides may be active in either eradicating established biofilms or preventing their formation, depending on the specific molecule. Here we present a detailed review of the literature describing the latest results of both in vitro and in vivo experiments aimed at evaluating AMP potential usage in biofilm control. In addition, we provide the reader with an overview on AMP local delivery systems, and we discuss their potential application in the coating of medical indwelling devices
In vitro anti-biofilm activity of a biphasic gentamicin-loaded calcium sulfate/hydroxyapatite bone graft substitute
Full text linkBone and implant-associated infections caused by microorganisms that grow in biofilms are difficult to treat because of persistence and recurrence of infection. Along with surgical debridement, the combination of systemic and local administration of antimicrobials represents the background for an efficient treatment strategy. Gentamicin is one of most used antibiotics for the local treatment of bone-related infections, alone or in combination, due to its bactericidal and broad-range activity. Gentamicin-loaded beads (GLBs), composed of calcium sulfate/hydroxyapatite, were assessed for their in vitro antimicrobial activity against planktonic and biofilm S. agalactiae, S. aureus, S. epidermidis, E. faecalis and E. coli, using standard methods and ultra-sensitive isothermal microcalorimetry. Gentamicin released from GLBs to clinically relevant concentrations (200–2500 μg/mL) within 1 h was able to kill planktonic S. agalactiae, S. epidermidis and E. coli at lower concentrations (MIC: ≤4 μg/mL). Moreover, 12 and 23 μg/mL of released gentamicin were able to prevent bacterial adhesion and suppress a 24 h-old biofilm of E. coli, respectively. Conversely, higher amounts of antibiotic, ranging from 171 to 1260 μg/mL, were needed to prevent and eradicate biofilms of gram-positive bacteria. Likewise, the emergence of resistance to GLBs in vitro and the bacterial attachment on the bone graft substitute, when the amount of gentamicin in the material is reduced, were also reported. This study provides further information regarding the in vitro anti-biofilm activity of the biphasic gentamicin-loaded bone graft substitute, suggesting the validity of this antibiotic-loaded material for the prophylaxis and treatment of bone and implant-associated infections
Diffusion Tensor Analysis by Two-Dimensional Pair Correlation of Fluorescence Fluctuations in Cells
Full text linkIn a living cell, the movement of biomolecules is highly regulated by the cellular organization into subcompartments that impose barriers to diffusion, can locally break the spatial isotropy, and ultimately guide these molecules to their targets. Despite the pivotal role of these processes, experimental tools to fully probe the complex connectivity (and accessibility) of the cell interior with adequate spatiotemporal resolution are still lacking. Here, we show how the heterogeneity of molecular dynamics and the location of barriers to molecular motion can be mapped in live cells by exploiting a two-dimensional (2D) extension of the pair correlation function (pCF) analysis. Starting from a time series of images collected for the same field of view, the resulting 2D pCF is calculated in the proximity of each point for each time delay and allows us to probe the spatial distribution of the molecules that started from a given pixel. This 2D pCF yields an accurate description of the preferential diffusive routes. Furthermore, we combine this analysis with the image-derived mean-square displacement approach and gain information on the average nanoscopic molecular displacements in different directions. Through these quantities, we build a fluorescence-fluctuation-based diffusion tensor that contains information on speed and directionality of the local dynamical processes. Contrary to classical fluorescence correlation spectroscopy and related methods, this combined approach can distinguish between isotropic and anisotropic local diffusion. We argue that the measurement of this iMSD tensor will contribute to advance our understanding of the role played by the intracellular environment in the regulation of molecular diffusion at the nanoscale
Bacteriophage Sb-1 enhances antibiotic activity against biofilm, degrades exopolysaccharide matrix and targets persisters of Staphylococcus aureus
Full text linkMost antibiotics have limited or no activity against bacterial biofilms, whereas bacteriophages can eradicate biofilms. We evaluated whether Staphylococcus aureus-specific bacteriophage Sb-1 could eradicate biofilm, both alone and in combination with different classes of antibiotics, degrade the extracellular matrix and target persister cells. Biofilm of methicillin-resistant S. aureus (MRSA) ATCC 43300 was treated with Sb-1 alone or in (simultaneous or staggered) combination with fosfomycin, rifampin, vancomycin, daptomycin or ciprofloxacin. The matrix was visualized by confocal fluorescent microscopy. Persister cells were treated with 104 and 107 plaque-forming units (PFU)/mL Sb-1 for 3 h in phosphate-buffered saline (PBS), followed by colony-forming units (CFU) counting. Alternatively, bacteria were washed and incubated in fresh brain heart infusion (BHI) medium and bacterial growth assessed after a further 24 h. Pretreatment with Sb-1 followed by the administration of subinhibitory concentrations of antibiotic caused a synergistic effect in eradicating MRSA biofilm. Sb-1 determined a dose-dependent reduction of matrix exopolysaccharide. Sb-1 at 107 PFU/mL showed direct killing activity on ≈ 5 × 105 CFU/mL persisters. However, even a lower titer had lytic activity when phage-treated persister cells were inoculated in fresh medium, reverting to a normal-growing phenotype. This study provides valuable data on the enhancing effect of Sb-1 on antibiotic efficacy, exhibiting specific antibiofilm features. Sb-1 can degrade the MRSA polysaccharide matrix and target persister cells and is therefore suitable for treatment of biofilm-associated infections
Daptomycin-loaded biodegradable thermosensitive hydrogels enhance drug stability and foster bactericidal activity against Staphylococcus aureus
Full text linkA drug delivery system based on fully biodegradable thermosensitive hydrogels enabling controlled antibiotic release may support the management of implant-associated infections. In this work, the lipopeptide antibiotic daptomycin was encapsulated in hydrogel networks consisting of vinyl sulfonated triblock copolymers of PEG-p(HPMAm-lac1,2) and thiolated hyaluronic acid. High concentrations of active daptomycin exceeding the minimum biofilm eradicating concentration were sustainably eluted from the biodegradable carrier
Bacteriophage therapy: an overview and the position of Italian Society of Infectious and Tropical Diseases
No full textIn recent years, the increase of antibiotic resistance and the lack in the pipeline of novel antimicrobial molecules make bacterial infections difficult to treat. Among European countries, Italy is the one region with a higher number of deaths caused by antibiotic-resistant bacteria. Moreover, a major concern is represented by biofilm-related infections. The ability of bacteria to form biofilm in presence of implanted-medical devices represents a further challenge for the treatment of bacterial infections. Thus, the development of alternative strategies to fight multi-drug resistant bacteria embedded in biofilms is an urgent need. Nowadays, bacteriophage therapy represents one of the potential and promising treatment options to overcome antibiotic resistance phenomenon. Bacteriophages are viruses capable to infect and replicate within bacterial cell. They are widespread in soil and water and play a role in microbial physiology. Since their discovery at the beginning of the twentieth century bacteriophages were used with therapeutic purposes against bacterial infections. However, the advent of the antibiotic era spurred medical doctors to abandon phage therapy in return for the most promising antibiotic therapy. For historical reasons, only few countries in the world, including Georgia, Russia and Poland have carried on the use of phages for therapeutic purposes and have developed specialised research and treatment centres, where phage therapy is permitted and applied to cure infectious disease. Although the efficacy of bacteriophages for treatment of infections is widely documented, the introduction of phage therapy in common management of bacterial infections in European hospital is hindered by the lack of an appropriate legal and regulatory framework. Different strategies have been used to overcome this problem, like the "Magistral Phage" preparation in Belgium. Here, we provide a review of the fundamental concept on bacteriophage therapy and propose this treatment as a possible alternative choice when antibiotics and surgery are not enough to eradicate a bacterial infection. We believe that the introduction of phage therapy in Italy might improve the quality of life of patients suffering of chronic bacterial infections and fight antibiotic resistances problem. To reach this goal the support and the promotion of Italian government and the scientific authorities is essential. SIMIT, the Italian Society of Infectious and Tropical Diseases, proposes to support the creation of an Italian Task Force to improve knowledge on bacteriophage therapy, collect stronger evidence about their efficacy and develop appropriate protocols for phage administration
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