Synergistic activity of dispersin B and cefamandole nafate in inhibition of staphylococcal biofilm growth on polyurethanes

Unraveling the interplay between unicellular parasites and bacterial biofilms: Implications for disease persistence and antibiotic resistance

Bacterial biofilms have attracted significant attention due to their involvement in persistent infections, food and water contamination, and infrastructure corrosion. This review delves into the intricate interactions between bacterial biofilms and unicellular parasites, shedding light on their impact on biofilm formation, structure, and function. Unicellular parasites, including protozoa, influence bacterial biofilms through grazing activities, leading to adaptive changes in bacterial communities. Moreover, parasites like Leishmania and Giardia can shape biofilm composition in a grazing independent manner, potentially influencing disease outcomes. Biofilms, acting as reservoirs, enable the survival of protozoan parasites against environmental stressors and antimicrobial agents. Furthermore, these biofilms may influence parasite virulence and stress responses, posing challenges in disease treatment. Interactions between unicellular parasites and fungal-containing biofilms is also discussed, hinting at complex microbial relationships in various ecosystems. Understanding these interactions offers insights into disease mechanisms and antibiotic resistance dissemination, paving the way for innovative therapeutic strategies and ecosystem-level implications.

Aggregatibacter actinomycetemcomitans Dispersin B: The Quintessential Antibiofilm Enzyme

The extracellular matrix of most bacterial biofilms contains polysaccharides, proteins, and nucleic acids. These biopolymers have been shown to mediate fundamental biofilm-related phenotypes including surface attachment, intercellular adhesion, and biocide resistance. Enzymes that degrade polymeric biofilm matrix components, including glycoside hydrolases, proteases, and nucleases, are useful tools for studying the structure and function of biofilm matrix components and are also being investigated as potential antibiofilm agents for clinical use. Dispersin B is a well-studied, broad-spectrum antibiofilm glycoside hydrolase produced by Aggregatibacter actinomycetemcomitans. Dispersin B degrades poly-N-acetylglucosamine, a biofilm matrix polysaccharide that mediates biofilm formation, stress tolerance, and biocide resistance in numerous Gram-negative and Gram-positive pathogens. Dispersin B has been shown to inhibit biofilm and pellicle formation; detach preformed biofilms; disaggregate bacterial flocs; sensitize preformed biofilms to detachment by enzymes, detergents, and metal chelators; and sensitize preformed biofilms to killing by antiseptics, antibiotics, bacteriophages, macrophages, and predatory bacteria. This review summarizes the results of nearly 100 in vitro and in vivo studies that have been carried out on dispersin B since its discovery 20 years ago. These include investigations into the biological function of the enzyme, its structure and mechanism of action, and its in vitro and in vivo antibiofilm activities against numerous bacterial species. Also discussed are potential clinical applications of dispersin B.

PDIA iminosugar influence on subcutaneous Staphylococcus aureus and Pseudomonas aeruginosa infections in mice

Introduction

Biofilm-associated infections persist as a therapeutic challenge in contemporary medicine. The efficacy of antibiotic therapies is ineffective in numerous instances, necessitating a heightened focus on exploring novel anti-biofilm medical strategies. Among these, iminosugars emerge as a distinctive class of compounds displaying promising biofilm inhibition properties.

Methods

This study employs an in vivo wound infection mouse model to evaluate the effectiveness of PDIA in treating biofilm-associated skin wound infections caused by Staphylococcus aureus and Pseudomonas aeruginosa. Dermic wounds in mice were infected with biofilm-forming strains, specifically S. aureus 48 and P. aeruginosa 5, which were isolated from patients with diabetic foot, and are well-known for their strong biofilm formation. The subsequent analysis included clinical, microbiological, and histopathological parameters. Furthermore, an exploration into the susceptibility of the infectious strains to hydrogen peroxide was conducted, acknowledging its potential presence during induced inflammation in mouse dermal wounds within an in vivo model.

Results

The findings revealed the efficacy of PDIA iminosugar against the S. aureus strain, evidenced by a reduction in bacterial numbers within the wound and the inflammatory focus.

Discussion

This study suggests that PDIA iminosugar emerges as an active and potentially effective antibiofilm agent, positioning it as a viable treatment option for staphylococcal infections.

Identification and characterization of TatD DNase in planarian Dugesia japonica and its antibiofilm effect

TatD DNase, a key enzyme in vertebrates and invertebrates, plays a pivotal role in various physiological processes. Dugesia japonica (D. japonica), a flatworm species, has remarkable regenerative capabilities and possesses a simplified immune system. However, the existence and biological functions of TatD DNase in D. japonica require further investigation. Here, we obtained the open reading frame (ORF) of DjTatD and demonstrated its conservation. The three-dimensional structure of DjTatD revealed its active site and binding mechanism. To investigate its enzymological properties, we overexpressed, purified, and characterized recombinant DjTatD (rDjTatD). We observed that DjTatD was primarily expressed in the pharynx and its expression could be significantly challenged upon stimulation with lipopolysaccharide, peptidoglycan, gram-positive and gram-negative bacteria. RNA interference results indicated that both DjTatD and DjDN2s play a role in pharyngeal regeneration and may serve as functional complements to each other. Additionally, we found that rDjTatD and recombinant T7DjTatD effectively reduce biofilm formation regardless of their bacterial origin. Together, our results demonstrated that DjTatD may be involved in the planarian immune response and pharyngeal regeneration. Furthermore, after further optimization in the future, rDjTatD and T7DjTatD can be considered highly effective antibiofilm agents.

Biofilm inhibition/eradication: exploring strategies and confronting challenges in combatting biofilm

Biofilms are complex communities of microorganisms enclosed in a self-produced extracellular matrix, posing a significant threat to different sectors, including healthcare and industry. This review provides an overview of the challenges faced due to biofilm formation and different novel strategies that can combat biofilm formation. Bacteria inside the biofilm exhibit increased resistance against different antimicrobial agents, including conventional antibiotics, which can lead to severe problems in livestock and animals, including humans. In addition, biofilm formation also imposes heavy economic pressure on industries. Hence it becomes necessary to explore newer alternatives to eradicate biofilms effectively without applying selection pressure on the bacteria. Excessive usage of antibiotics may also lead to an increase in the number of resistant strains as bacteria employ an advanced antimicrobial resistance mechanism. This review provides insight into multifaceted technologies like quorum sensing inhibition, enzymes, antimicrobial peptides, bacteriophage, phytocompounds, and nanotechnology to neutralize biofilms without developing antimicrobial resistance (AMR). Furthermore, it will pave the way for developing newer therapeutic agents to deal with biofilms more efficiently.

An apparent lack of synergy between degradative enzymes against Staphylococcus aureus biofilms

Enzymes combat bacterial infections by degrading biomolecules to disperse Staphylococcus aureus biofilms. Commercial enzyme mixtures, like cellulase and pepsin, show concentration-dependent dispersion, but low concentrations lack synergy. Only the sequential addition of pepsin followed by Arthrobacter luteus zymolyase 20T displays synergy, effectively dispersing biofilms. Purified zymolyase 100T outperforms zymolyase 20T but lacks synergy with pepsin. This study underscores the complexity of enzymatic biofilm dispersal, highlighting the need for tailored approaches based on enzyme properties and biofilm composition.

Antibiotic Resistant Biofilms and the Quest for Novel Therapeutic Strategies

Antimicrobial resistance (AMR) is one of the major leading causes of death around the globe. Present treatment pipelines are insufficient to overcome the critical situation. Prominent biofilm forming human pathogens which can thrive in infection sites using adaptive features results in biofilm persistence. Considering the present scenario, prudential investigations into the mechanisms of resistance target them to improve antibiotic efficacy is required. Regarding this, developing newer and effective treatment options using edge cutting technologies in medical research is the need of time. The reasons underlying the adaptive features in biofilm persistence have been centred on different metabolic and physiological aspects. The high tolerance levels against antibiotics direct researchers to search for novel bioactive molecules that can help combat the problem. In view of this, the present review outlines the focuses on an opportunity of different strategies which are in testing pipeline can thus be developed into products ready to use.

Quenching and quorum sensing in bacterial bio-films

Quorum sensing (QS) is the ability of bacteria to monitor their population density and adjust gene expression accordingly. QS-regulated processes include host-microbe interactions, horizontal gene transfer, and multicellular behaviours (such as the growth and development of biofilm). The creation, transfer, and perception of bacterial chemicals known as autoinducers or QS signals are necessary for QS signalling (e.g. N-acylhomoserine lactones). Quorum quenching (QQ), another name for the disruption of QS signalling, comprises a wide range of events and mechanisms that are described and analysed in this study. In order to better comprehend the targets of the QQ phenomena that organisms have naturally developed and are currently being actively researched from practical perspectives, we first surveyed the diversity of QS-signals and QS-associated responses. Next, the mechanisms, molecular players, and targets related to QS interference are discussed, with a focus on natural QQ enzymes and compounds that function as QS inhibitors. To illustrate the processes and biological functions of QS inhibition in microbe-microbe and host-microbe interactions, a few QQ paradigms are described in detail. Finally, certain QQ techniques are offered as potential instruments in a variety of industries, including agriculture, medical, aquaculture, crop production, and anti-biofouling areas.

The Effect of Ficin Immobilized on Carboxymethyl Chitosan on Biofilms of Oral Pathogens

In the last decade, Ficin, a proteolytic enzyme extracted from the latex sap of the wild fig tree, has been widely investigated as a promising tool for the treatment of microbial biofilms, wound healing, and oral care. Here we report the antibiofilm properties of the enzyme immobilized on soluble carboxymethyl chitosan (CMCh) and CMCh itself. Ficin was immobilized on CMCh with molecular weights of either 200, 350 or 600 kDa. Among them, the carrier with a molecular weight of 200 kDa bound the maximum amount of enzyme, binding up to 49% of the total protein compared to 19-32% of the total protein bound to other CMChs. Treatment with pure CMCh led to the destruction of biofilms formed by Streptococcus salivarius, Streptococcus gordonii, Streptococcus mutans, and Candida albicans, while no apparent effect on Staphylococcus aureus was observed. A soluble Ficin was less efficient in the destruction of the biofilms formed by Streptococcus sobrinus and S. gordonii. By contrast, treatment with CMCh200-immobilized Ficin led to a significant reduction of the biofilms of the primary colonizers S. gordonii and S. mutans. In model biofilms obtained by the inoculation of swabs from teeth of healthy volunteers, the destruction of the biofilm by both soluble and immobilized Ficin was observed, although the degree of the destruction varied between artificial plaque samples. Nevertheless, combined treatment of oral Streptococci biofilm by enzyme and chlorhexidine for 3 h led to a significant decrease in the viability of biofilm-embedded cells, compared to solely chlorhexidine application. This suggests that the use of either soluble or immobilized Ficin would allow decreasing the amount and/or concentration of the antiseptics required for oral care or improving the efficiency of oral cavity sanitization.

Pseudomonas aeruginosa biofilm exopolysaccharides: assembly, function, and degradation

The biofilm matrix is a fortress; sheltering bacteria in a protective and nourishing barrier that allows for growth and adaptation to various surroundings. A variety of different components are found within the matrix including water, lipids, proteins, extracellular DNA, RNA, membrane vesicles, phages, and exopolysaccharides. As part of its biofilm matrix, Pseudomonas aeruginosa is genetically capable of producing three chemically distinct exopolysaccharides - alginate, Pel, and Psl - each of which has a distinct role in biofilm formation and immune evasion during infection. The polymers are produced by highly conserved mechanisms of secretion, involving many proteins that span both the inner and outer bacterial membranes. Experimentally determined structures, predictive modelling of proteins whose structures are yet to be solved, and structural homology comparisons give us insight into the molecular mechanisms of these secretion systems, from polymer synthesis to modification and export. Here, we review recent advances that enhance our understanding of P. aeruginosa multiprotein exopolysaccharide biosynthetic complexes, and how the glycoside hydrolases/lyases within these systems have been commandeered for antimicrobial applications.

An apparent lack of synergy between degradative enzymes against Staphylococcus aureus biofilms

The use of enzymes represents an approach to combat bacterial infections by degrading extracellular biomolecules to disperse Staphylococcus aureus biofilms. Commercial enzyme preparations, including cellulase, amylase, pectinase, zymolyase, and pepsin, exhibit concentration-dependent dispersion of S. aureus biofilms. Here, we report that low concentrations of these enzymes generally lack synergy when combined or added together sequentially to biofilms. Only the addition of a protease (pepsin) followed by a commercial mixture of degradative enzymes from Arthrobacter luteus (zymolyase 20T), demonstrated synergy and was effective at dispersing S. aureus biofilms. A more purified mixture of Arthrobacter luteus enzymes (zymolyase 100T) showed improved dispersal of S. aureus biofilms compared to zymolyase 20T but lacked synergy with pepsin. This study emphasizes the complexity of enzymatic biofilm dispersal and the need for tailored approaches based on the properties of degradative enzymes and biofilm composition.

Modification of Dispersin B with Cyclodextrin-Ciprofloxacin Derivatives for Treating Staphylococcal

To address the high tolerance of biofilms to antibiotics, it is urgent to develop new strategies to fight against these bacterial consortia. An innovative antibiofilm nanovector drug delivery system, consisting of Dispersin B-permethylated-β-cyclodextrin/ciprofloxacin adamantyl (DspB-β-CD/CIP-Ad), is described here. For this purpose, complexation assays between CIP-Ad and (i) unmodified β-CD and (ii) different derivatives of β-CD, which are 2,3-O-dimethyl-β-CD, 2,6-O-dimethyl-β-CD, and 2,3,6-O-trimethyl-β-CD, were tested. A stoichiometry of 1/1 was obtained for the β-CD/CIP-Ad complex by NMR analysis. Isothermal Titration Calorimetry (ITC) experiments were carried out to determine Ka, ΔH, and ΔS thermodynamic parameters of the complex between β-CD and its different derivatives in the presence of CIP-Ad. A stoichiometry of 1/1 for β-CD/CIP-Ad complexes was confirmed with variable affinity according to the type of methylation. A phase solubility study showed increased CIP-Ad solubility with CD concentration, pointing out complex formation. The evaluation of the antibacterial activity of CIP-Ad and the 2,3-O-dimethyl-β-CD/CIP-Ad or 2,3,6-O-trimethyl-β-CD/CIP-Ad complexes was performed on Staphylococcus epidermidis (S. epidermidis) strains. The Minimum Inhibitory Concentration (MIC) studies showed that the complex of CIP-Ad and 2,3-O-dimethyl-β-CD exhibited a similar antimicrobial activity to CIP-Ad alone, while the interaction with 2,3,6-O-trimethyl-β-CD increased MIC values. Antimicrobial assays on S. epidermidis biofilms demonstrated that the synergistic effect observed with the DspB/CIP association was partly maintained with the 2,3-O-dimethyl-β-CDs/CIP-Ad complex. To obtain this "all-in-one" drug delivery system, able to destroy the biofilm matrix and release the antibiotic simultaneously, we covalently grafted DspB on three carboxylic permethylated CD derivatives with different-length spacer arms. The strategy was validated by demonstrating that a DspB-permethylated-β-CD/ciprofloxacin-Ad system exhibited efficient antibiofilm activity.

Understanding bacterial biofilms: From definition to treatment strategies

Bacterial biofilms are complex microbial communities encased in extracellular polymeric substances. Their formation is a multi-step process. Biofilms are a significant problem in treating bacterial infections and are one of the main reasons for the persistence of infections. They can exhibit increased resistance to classical antibiotics and cause disease through device-related and non-device (tissue) -associated infections, posing a severe threat to global health issues. Therefore, early detection and search for new and alternative treatments are essential for treating and suppressing biofilm-associated infections. In this paper, we systematically reviewed the formation of bacterial biofilms, associated infections, detection methods, and potential treatment strategies, aiming to provide researchers with the latest progress in the detection and treatment of bacterial biofilms.

Biofilm control strategies in the light of biofilm-forming microorganisms

Biofilm is a complex consortium of microorganisms attached to biotic or abiotic surfaces and live in self-produced or acquired extracellular polymeric substances (EPSs). EPSs are mainly formed by lipids, polysaccharides, proteins, and extracellular DNAs. The adherence to the surface of microbial communities is seen in food, medical, dental, industrial, and environmental fields. Biofilm development in food processing areas challenges food hygiene, and human health. In addition, bacterial attachment and biofilm formation on medical implants inside human tissue can cause multiple critical chronic infections. More than 30 years of international research on the mechanisms of biofilm formation have been underway to address concerns about bacterial biofilm infections. Antibiofilm strategies contain cold atmospheric plasma, nanotechnological, phage-based, antimicrobial peptides, and quorum sensing inhibition. In the last years, the studies on environmentally-friendly techniques such as essential oils and bacteriophages have been intensified to reduce microbial growth. However, the mechanisms of the biofilm matrix formation are still unclear. This review aims to discuss the latest antibiofilm therapeutic strategies against biofilm-forming bacteria.

The Role of Coagulase-Negative Staphylococci Biofilms on Late-Onset Sepsis: Current Challenges and Emerging Diagnostics and Therapies

Infections are one of the most significant complications of neonates, especially those born preterm, with sepsis as one of the principal causes of mortality. Coagulase-negative staphylococci (CoNS), a group of staphylococcal species that naturally inhabit healthy human skin and mucosa, are the most common cause of late-onset sepsis, especially in preterms. One of the risk factors for the development of CoNS infections is the presence of implanted biomedical devices, which are frequently used for medications and/or nutrient delivery, as they serve as a scaffold for biofilm formation. The major concerns related to CoNS infections have to do with the increasing resistance to multiple antibiotics observed among this bacterial group and biofilm cells’ increased tolerance to antibiotics. As such, the treatment of CoNS biofilm-associated infections with antibiotics is increasingly challenging and considering that antibiotics remain the primary form of treatment, this issue will likely persist in upcoming years. For that reason, the development of innovative and efficient therapeutic measures is of utmost importance. This narrative review assesses the current challenges and emerging diagnostic tools and therapies for the treatment of CoNS biofilm-associated infections, with a special focus on late-onset sepsis.

Fungal Glycoside Hydrolases Display Unique Specificities for Polysaccharides and Staphylococcus aureus Biofilms

Commercially available cellulases and amylases can disperse the pathogenic bacteria embedded in biofilms. This suggests that polysaccharide-degrading enzymes would be useful as antibacterial therapies to aid the treatment of biofilm-associated bacteria, e.g., in chronic wounds. Using a published enzyme library, we explored the capacity of 76 diverse recombinant glycoside hydrolases to disperse Staphylococcus aureus biofilms. Four of the 76 recombinant glycoside hydrolases digested purified cellulose, amylose, or pectin. However, these enzymes did not disperse biofilms, indicating that anti-biofilm activity is not general to all glycoside hydrolases and that biofilm activity cannot be predicted from the activity on pure substrates. Only one of the 76 recombinant enzymes was detectably active in biofilm dispersion, an α-xylosidase from Aspergillus nidulans. An α-xylosidase cloned subsequently from Aspergillus thermomutatus likewise demonstrated antibiofilm activity, suggesting that α-xylosidases, in general, can disperse Staphylococcus biofilms. Surprisingly, neither of the two β-xylosidases in the library degraded biofilms. Commercial preparations of amylase and cellulase that are known to be effective in the dispersion of Staphylococcus biofilms were also analyzed. The commercial cellulase contained contaminating proteins with multiple enzymes exhibiting biofilm-dispersing activity. Successfully prospecting for additional antibiofilm enzymes may thus require large libraries and may benefit from purified enzymes. The complexity of biofilms and the diversity of glycoside hydrolases continue to make it difficult to predict or understand the enzymes that could have future therapeutic applications.

The role of nanocomposites against biofilm infections in humans

The use of nanomaterials in several fields of science has undergone a revolution in the last few decades. It has been reported by the National Institutes of Health (NIH) that 65% and 80% of infections are accountable for at least 65% of human bacterial infections. One of their important applications in healthcare is the use of nanoparticles (NPs) to eradicate free-floating bacteria and those that form biofilms. A nanocomposite (NC) is a multiphase stable fabric with one or three dimensions that are much smaller than 100 nm, or systems with nanoscale repeat distances between the unique phases that make up the material. Using NC materials to get rid of germs is a more sophisticated and effective technique to destroy bacterial biofilms. These biofilms are refractory to standard antibiotics, mainly to chronic infections and non-healing wounds. Materials like graphene and chitosan can be utilized to make several forms of NCs, in addition to different metal oxides. The ability of NCs to address the issue of bacterial resistance is its main advantage over antibiotics. This review highlights the synthesis, characterization, and mechanism through which NCs disrupt Gram-positive and Gram-negative bacterial biofilms, and their relative benefits and drawbacks. There is an urgent need to develop materials like NCs with a larger spectrum of action due to the rising prevalence of human bacterial diseases that are multidrug-resistant and form biofilms.

The Bovhyaluronidase Azoximer (Longidaza®) Disrupts Candida albicans and Candida albicans-Bacterial Mixed Biofilms and Increases the Efficacy of Antifungals

Background and Objectives: Candida albicans causes various diseases ranging from superficial mycoses to life-threatening systemic infections often associated with biofilm formation, including mixed fungal−bacterial consortia. The biofilm matrix protects cells, making Candida extremely resistant to treatment. Here, we show that the bovhyaluronidase azoximer (Longidaza®) in vitro destroys the biofilm formed by either C. albicans alone or mixed with bacteria, this way decreasing the concentrations of antimicrobials required for the pathogen’s eradication. Materials and Methods: Bovhyaluronidase azoximer, Longidaza® was obtained from NPO Petrovax Pharm Ltd., Moscow, Russia as lyophilized powder. The antifungal activity was assessed by microdilution assay and CFUs counting. Antibiofilm activity was evaluated via biofilms staining and scanning electron microscopy. Results: Thus, treatment with Longidaza® reduced the biofilm biomass of nine C. albicans clinical isolates by 30−60%, while mixed biofilms of C. albicans with various bacteria were destroyed by 30−40%. Furthermore, the concentration of fluconazole required to achieve a similar reduction of the residual respiratory activity of detached cell clumps of four C. albicans isolates has been reduced four-fold when combined with Longidaza®. While in the biofilm, two of four isolates became significantly more susceptible to fluconazole in combination with Longidaza®. Conclusion: Taken together, our data indicate that Longidaza® is capable of suppression of tissues and artificial surfaces biofouling by C. albicans biofilms, as well as facilitating drug penetration into the cell clumps, this way decreasing the effective MIC of antifungals.

Targeted Anti-Biofilm Therapy: Dissecting Targets in the Biofilm Life Cycle

Biofilm is a crucial virulence factor for microorganisms that causes chronic infection. After biofilm formation, the bacteria present improve drug tolerance and multifactorial defense mechanisms, which impose significant challenges for the use of antimicrobials. This indicates the urgent need for new targeted technologies and emerging therapeutic strategies. In this review, we focus on the current biofilm-targeting strategies and those under development, including targeting persistent cells, quorum quenching, and phage therapy. We emphasize biofilm-targeting technologies that are supported by blocking the biofilm life cycle, providing a theoretical basis for design of targeting technology that disrupts the biofilm and promotes practical application of antibacterial materials.

An Overview of Biofilm Formation-Combating Strategies and Mechanisms of Action of Antibiofilm Agents

Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.

Colonization and Infection of Indwelling Medical Devices by Staphylococcus aureus with an Emphasis on Orthopedic Implants

The use of indwelling medical devices has constantly increased in recent years and has revolutionized the quality of life of patients affected by different diseases. However, despite the improvement of hygiene conditions in hospitals, implant-associated infections remain a common and serious complication in prosthetic surgery, mainly in the orthopedic field, where infection often leads to implant failure. Staphylococcus aureus is the most common cause of biomaterial-centered infection. Upon binding to the medical devices, these bacteria proliferate and develop dense communities encased in a protective matrix called biofilm. Biofilm formation has been proposed as occurring in several stages-(1) attachment; (2) proliferation; (3) dispersal-and involves a variety of host and staphylococcal proteinaceous and non-proteinaceous factors. Moreover, biofilm formation is strictly regulated by several control systems. Biofilms enable staphylococci to avoid antimicrobial activity and host immune response and are a source of persistent bacteremia as well as of localized tissue destruction. While considerable information is available on staphylococcal biofilm formation on medical implants and important results have been achieved on the treatment of biofilms, preclinical and clinical applications need to be further investigated. Thus, the purpose of this review is to gather current studies about the mechanism of infection of indwelling medical devices by S. aureus with a special focus on the biochemical factors involved in biofilm formation and regulation. We also provide a summary of the current therapeutic strategies to combat biomaterial-associated infections and highlight the need to further explore biofilm physiology and conduct research for innovative anti-biofilm approaches.

Microbially-derived cocktail of carbohydrases as an anti-biofouling agents: a 'green approach'

Enzymes, also known as biocatalysts, display vital properties like high substrate specificity, an eco-friendly nature, low energy inputs, and cost-effectiveness. Among their numerous known applications, enzymes that can target biofilms or their components are increasingly being investigated for their anti-biofouling action, particularly in healthcare, food manufacturing units and environmental applications. Enzymes can target biofilms at different levels like during the attachment of microorganisms, formation of exopolymeric substances (EPS), and their disruption thereafter. In this regard, a consortium of carbohydrases that can target heterogeneous polysaccharides present in the EPS matrix may provide an effective alternative to conventional chemical anti-biofouling methods. Further, for complete annihilation of biofilms, enzymes can be used alone or in conjunction with other antimicrobial agents. Enzymes hold the promise to replace the conventional methods with greener, more economical, and more efficient alternatives. The present article explores the potential and future perspectives of using carbohydrases as effective anti-biofilm agents.

Biofilm Formation by Pathogenic Bacteria: Applying a Staphylococcus aureus Model to Appraise Potential Targets for Therapeutic Intervention

Carried in the nasal passages by up to 30% of humans, Staphylococcus aureus is recognized to be a successful opportunistic pathogen. It is a frequent cause of infections of the upper respiratory tract, including sinusitis, and of the skin, typically abscesses, as well as of food poisoning and medical device contamination. The antimicrobial resistance of such, often chronic, health conditions is underpinned by the unique structure of bacterial biofilm, which is the focus of increasing research to try to overcome this serious public health challenge. Due to the protective barrier of an exopolysaccharide matrix, bacteria that are embedded within biofilm are highly resistant both to an infected individual’s immune response and to any treating antibiotics. An in-depth appraisal of the stepwise progression of biofilm formation by S. aureus, used as a model infection for all cases of bacterial antibiotic resistance, has enhanced understanding of this complicated microscopic structure and served to highlight possible intervention targets for both patient cure and community infection control. While antibiotic therapy offers a practical means of treatment and prevention, the most favorable results are achieved in combination with other methods. This review provides an overview of S. aureus biofilm development, outlines the current range of anti-biofilm agents that are used against each stage and summarizes their relative merits.

Functional Immobilization of a Biofilm-Releasing Glycoside Hydrolase Dispersin B on Magnetic Nanoparticles

Dispersin B (DspB) is a member of glycoside hydrolase family 20 (GH20) and catalyzes degradation of biofilms forming by pathogenic bacteria such as Staphylococcus aureus. Magnetoreceptor (MagR) is a magnetic protein that can be used as a fusion partner for functionally immobilizing proteins on magnetic surfaces. In the present study, a recombinant protein DspB-MagR was constructed by fusing MagR to the C-terminus of DspB and expressed in Escherichia coli. Magnetic immobilization of purified DspB-MagR on magnetic core-shell structured Fe3O4@SiO2 nanoparticles was achieved and characterized by means of various techniques including SDS-PAGE, Fourier transform infrared spectroscopy, thermogravimetric analysis, zeta potential measurement, and scanning electron microscopy. It was evaluated the influence of temperature, pH, and storage time on the performance of immobilized DspB-MagR on Fe3O4@SiO2 nanoparticles. Removal of biofilms forming by Staphylococcus aureus and other medical sourced bacterial species was achieved by using Fe3O4@SiO2 nanoparticles loading with DspB-MagR. This work promoted potential applications of DspB and similar enzymes for medical purposes.

The Two Weapons against Bacterial Biofilms: Detection and Treatment

Bacterial biofilms are defined as complex aggregates of bacteria that grow attached to surfaces or are associated with interfaces. Bacteria within biofilms are embedded in a self-produced extracellular matrix made of polysaccharides, nucleic acids, and proteins. It is recognized that bacterial biofilms are responsible for the majority of microbial infections that occur in the human body, and that biofilm-related infections are extremely difficult to treat. This is related with the fact that microbial cells in biofilms exhibit increased resistance levels to antibiotics in comparison with planktonic (free-floating) cells. In the last years, the introduction into the market of novel compounds that can overcome the resistance to antimicrobial agents associated with biofilm infection has slowed down. If this situation is not altered, millions of lives are at risk, and this will also strongly affect the world economy. As such, research into the identification and eradication of biofilms is important for the future of human health. In this sense, this article provides an overview of techniques developed to detect and imaging biofilms as well as recent strategies that can be applied to treat biofilms during the several biofilm formation steps.

Multifunctional fluorescent probes for high-throughput characterization of hexosaminidase enzyme activity

Microbial polysaccharides composed of N-acetylglucosamine (GlcNAc), such as chitin, peptidoglycan and poly-β-(1 → 6)-GlcNAc (dPNAG), play a critical role in maintaining cell integrity or in facilitating biofilm formation in numerous fungal and bacterial pathogens. Glycosyl hydrolase enzymes that catalyze the degradation of these β-GlcNAc containing polysaccharides play important roles in normal microbial cell physiology and can also be exploited as biocatalysts with applications as anti-fungal, anti-bacterial, or biofilm dispersal agents. Assays to rapidly detect and characterize the activity of such glycosyl hydrolase enzymes can facilitate their development as biocatalyst, however, currently available probes such as 4-methylumbelliferyl-β-GlcNAc (4MU-GlcNAc) are not universally accepted as substrates, and their fluorescent signal is sensitive to changes in pH. Here, we present the development of a new multifunctional fluorescent substrate analog for the detection and characterization of hexosaminidase enzyme activity containing a 7-amino-4-methyl coumarin (AMC) carbamate aglycone. This probe is widely tolerated as a substrate for exo-acting β-hexosaminidase, family 19 endo-chitinase, and the dPNAG hydrolase enzyme Dispersin B (DspB) and enables detection of hexosaminidase enzyme activity via either single wavelength fluorescent measurements or ratiometric fluorescent detection. We demonstrate the utility of this probe to screen for recombinant DspB activity in Escherichia coli cell lysates, and for the development of a high-throughput assay to screen for DspB inhibitors.

Biomaterials and technologies in the management of periprosthetic infection after total hip arthroplasty: An updated review

Although total hip arthroplasty (THA) is considered one of the most efficacious procedures for managing various hip conditions, failures due to different mechanisms are still being reported. Periprosthetic joint infection (PJI) is one of the devastating causes of failure and revision of THA. PJI carries a burden on the patient, the surgeon, and the health-care system. The diagnosis and management of PJIs carry many morbidities and increased treatment costs. The development of PJI is multifactorial, including issues related to the patient’s general condition, the surgeon’s efficiency, surgical technique, and the implants used. Recent advances in the area of diagnosis and predicting PJI as well as introducing new technologies and biomaterials update for the prevention and treatment of PJI. Local implant coatings, advancement in the bearing surfaces technologies, and new technologies such as immunotherapy and bacteriophage therapy were introduced and suggested as contemporary PJI eradication solutions. In this review, we aimed at discussing some of the newly introduced materials and technologies for the sake of PJI control.

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure-property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.

Pulmonary biofilm-based chronic infections and inhaled treatment strategies

Certain pulmonary diseases, such as cystic fibrosis (CF), non-CF bronchiectasis, chronic obstructive pulmonary disease, and ventilator-associated pneumonia, are usually accompanied by respiratory tract infections due to the physiological alteration of the lung immunological defenses. Recurrent infections may lead to chronic infection through the formation of biofilms. Chronic biofilm-based infections are challenging to treat using antimicrobial agents. Therefore, effective ways to eradicate biofilms and thus relieve respiratory tract infection require the development of efficacious agents for biofilm destruction, the design of delivery carriers with biofilm-targeting and/or penetrating abilities for these agents, and the direct delivery of them into the lung. This review provides an in-depth description of biofilm-based infections caused by pulmonary diseases and focuses on current existing agents that are administered by inhalation into the lung to treat biofilm, which include i) inhalable antimicrobial agents and their combinations, ii) non-antimicrobial adjuvants such as matrix-targeting enzymes, mannitol, glutathione, cyclosporin A, and iii) liposomal formulations of anti-biofilm agents. Finally, novel agents that have shown promise against pulmonary biofilms as well as traditional and new devices for pulmonary delivery of anti-biofilm agents into the lung are also discussed.

Novel treatment dynamics for biofilm-related infections

Introduction: As a result of progress in medical care, a huge number of medical devices are used in the treatment of human diseases. In turn, biofilm-related infection has become a growing threat due to the tolerance of biofilms to antimicrobials, a problem magnified by the development of antimicrobial resistance worldwide. As a result, successful treatment of biofilm-disease using only antimicrobials is problematic.Areas covered: We summarize some alternative approaches to classic antimicrobials for the treatment of biofilm disease. This review is not intended to be exhaustive but to give a clinical picture of alternatives to antimicrobial agents to manage biofilm disease. We highlight those strategies that may be closer to application in clinical practice.Expert opinion: There are a number of outstanding challenges in the development of novel antibiofilm therapies. Screening for effective antibiofilm compounds requires models relevant to all clinical scenarios. Although in vitro research of anti-biofilm strategies has progressed significantly over the past decade, there is a lack of in vivo research. In addition, the complexity of biofilm biology makes it difficult to develop a compound that is likely to provide the single 'magic bullet'. The multifaceted nature of biofilms imposes the need for multi-targeted or combinatorial therapies.

Novel Approaches to Combat Medical Device-Associated BioFilms

Biofilms are aggregates formed as a protective survival state by microorganisms to adapt to the environment and can be resistant to antimicrobial agents and host immune responses due to chemical or physical diffusion barriers, modified nutrient environments, suppression of the growth rate within biofilms, and the genetic adaptation of cells within biofilms. With the widespread use of medical devices, medical device-associated biofilms continue to pose a serious threat to human health, and these biofilms have become the most important source of nosocomial infections. However, traditional antimicrobial agents cannot completely eliminate medical device-associated biofilms. New strategies for the treatment of these biofilms and targeting biofilm infections are urgently required. Several novel approaches have been developed and identified as effective and promising treatments. In this review, we briefly summarize the challenges associated with the treatment of medical device-associated biofilm infections and highlight the latest promising approaches aimed at preventing or eradicating these biofilms.

Biofilms by bacterial human pathogens: Clinical relevance - development, composition and regulation - therapeutical strategies

Notably, bacterial biofilm formation is increasingly recognized as a passive virulence factor facilitating many infectious disease processes. In this review we will focus on bacterial biofilms formed by human pathogens and highlight their relevance for diverse diseases. Along biofilm composition and regulation emphasis is laid on the intensively studied biofilms of Vibrio cholerae, Pseudomonas aeruginosa and Staphylococcus spp., which are commonly used as biofilm model organisms and therefore contribute to our general understanding of bacterial biofilm (patho-)physiology. Finally, therapeutical intervention strategies targeting biofilms will be discussed.

Lactobacilli postbiotics reduce biofilm formation and alter transcription of virulence genes of Aggregatibacter actinomycetemcomitans

Periodontitis is characterized by a dysbiotic microbial community and treatment strategies include the reestablishment of symbiosis by reducing pathogens abundance. Aggregatibacter actinomycetemcomitans (Aa) is frequently associated with rapidly progressing periodontitis. Since the oral ecosystem may be affected by metabolic end-products of bacteria, we evaluated the effect of soluble compounds released by probiotic lactobacilli, known as postbiotics, on Aa biofilm and expression of virulence-associated genes. Cell-free pH-neutralized supernatants (CFS) of Lactobacillus rhamnosus Lr32, L. rhamnosus HN001, Lactobacillus acidophilus LA5, and L. acidophilus NCFM were tested against a fimbriated clinical isolate of Aa JP2 genotype (1 × 10⁷  CFU/well) on biofilm formation for 24 hr, and early and mature preformed biofilms (2 and 24 hr). Lactobacilli CFS partially reduced Aa viable counts and biofilms biomass, but did not affect the number of viable non-adherent bacteria, except for LA5 CFS. Furthermore, LA5 CFS and, in a lesser extent HN001 CFS, influenced Aa preformed biofilms. Lactobacilli postbiotics altered expression profile of Aa in a strain-specific fashion. Transcription of cytolethal distending toxin (cdtB) and leukotoxin (ltxA) was downregulated by CFS of LA5 and LR32 CFS. Although all probiotics produced detectable peroxide, transcription of katA was downregulated by lactobacilli CFS. Transcription of dspB was abrogated by LR32 and NCFM CFS, but increased by HN001, whereas expression of pgA was not affected by any postbiotic. Our data indicated the potential of postbiotics from lactobacilli, especially LA5, to reduce colonization levels of Aa and to modulate the expression of virulence factors implicated in evasion of host defenses.

Biofilms as Promoters of Bacterial Antibiotic Resistance and Tolerance

Multidrug resistant bacteria are a global threat for human and animal health. However, they are only part of the problem of antibiotic failure. Another bacterial strategy that contributes to their capacity to withstand antimicrobials is the formation of biofilms. Biofilms are associations of microorganisms embedded a self-produced extracellular matrix. They create particular environments that confer bacterial tolerance and resistance to antibiotics by different mechanisms that depend upon factors such as biofilm composition, architecture, the stage of biofilm development, and growth conditions. The biofilm structure hinders the penetration of antibiotics and may prevent the accumulation of bactericidal concentrations throughout the entire biofilm. In addition, gradients of dispersion of nutrients and oxygen within the biofilm generate different metabolic states of individual cells and favor the development of antibiotic tolerance and bacterial persistence. Furthermore, antimicrobial resistance may develop within biofilms through a variety of mechanisms. The expression of efflux pumps may be induced in various parts of the biofilm and the mutation frequency is induced, while the presence of extracellular DNA and the close contact between cells favor horizontal gene transfer. A deep understanding of the mechanisms by which biofilms cause tolerance/resistance to antibiotics helps to develop novel strategies to fight these infections.

Anionic amino acids support hydrolysis of poly-β-(1,6)-N-acetylglucosamine exopolysaccharides by the biofilm dispersing glycosidase Dispersin B

The exopolysaccharide poly-β-(1→6)-N-acetylglucosamine (PNAG) is a major structural determinant of bacterial biofilms responsible for persistent and nosocomial infections. The enzymatic dispersal of biofilms by PNAG-hydrolyzing glycosidase enzymes, such as Dispersin B (DspB), is a possible approach to treat biofilm-dependent bacterial infections. The cationic charge resulting from partial de-N-acetylation of native PNAG is critical for PNAG-dependent biofilm formation. We recently demonstrated that DspB has increased catalytic activity on de-N-acetylated PNAG oligosaccharides, but the molecular basis for this increased activity is not known. Here, we analyze the role of anionic amino acids surrounding the catalytic pocket of DspB in PNAG substrate recognition and hydrolysis using a combination of site-directed mutagenesis, activity measurements using synthetic PNAG oligosaccharide analogs, and in vitro biofilm dispersal assays. The results of these studies support a model in which bound PNAG is weakly associated with a shallow anionic groove on the DspB protein surface with recognition driven by interactions with the -1 GlcNAc residue in the catalytic pocket. An increased rate of hydrolysis for cationic PNAG was driven, in part, by interaction with D147 on the anionic surface. Moreover, we identified that a DspB mutant with improved hydrolysis of fully acetylated PNAG oligosaccharides correlates with improved in vitro dispersal of PNAG-dependent Staphylococcus epidermidis biofilms. These results provide insight into the mechanism of substrate recognition by DspB and suggest a method to improve DspB biofilm dispersal activity by mutation of the amino acids within the anionic binding surface.

A Glance at Antimicrobial Strategies to Prevent Catheter-Associated Medical Infections

Urinary and intravascular catheters are two of the most used invasive medical devices; however, microbial colonization of catheter surfaces is responsible for most healthcare-associated infections (HAIs). Several antimicrobial-coated catheters are available, but recurrent antibiotic therapy can decrease their potential activity against resistant bacterial strains. The aim of this Review is to question the actual effectiveness of currently used (coated) catheters and describe the progress and promise of alternative antimicrobial coatings. Different strategies have been reviewed with the common goal of preventing biofilm formation on catheters, including release-based approaches using antibiotics, antiseptics, nitric oxide, 5-fluorouracil, and silver as well as contact-killing approaches employing quaternary ammonium compounds, chitosan, antimicrobial peptides, and enzymes. All of these strategies have given proof of antimicrobial efficacy by modifying the physiology of pathogens or disrupting their structural integrity. The aim for synergistic approaches using multitarget processes and the combination of both antifouling and bactericidal properties holds potential for the near future. Despite intensive research in biofilm preventive strategies, laboratorial studies still present some limitations since experimental conditions usually are not the same and also differ from biological conditions encountered when the catheter is inserted in the human body. Consequently, in most cases, the efficacy data obtained from in vitro studies is not properly reflected in the clinical setting. Thus, further well-designed clinical trials and additional cytotoxicity studies are needed to prove the efficacy and safety of the developed antimicrobial strategies in the prevention of biofilm formation at catheter surfaces.

Biofilm dispersion: The key to biofilm eradication or opening Pandora's box?

Biofilms are extremely difficult to eradicate due to their decreased antibiotic susceptibility. Inducing biofilm dispersion could be a potential strategy to help combat biofilm-related infections. Mechanisms of biofilm dispersion can basically be divided into two groups, i.e. active and passive dispersion. Active dispersion depends on a decrease in the intracellular c-di-GMP levels, leading to the production of enzymes that degrade the biofilm matrix and promote dispersion. In contrast, passive dispersion relies on triggers that directly release cells from the biofilm. In the present review, several active and passive dispersion strategies are discussed. In addition, the disadvantages and possible consequences of using dispersion as a treatment approach for biofilm-related infections are also reviewed.

Bidirectional alterations in antibiotics susceptibility in Staphylococcus aureus-Pseudomonas aeruginosa dual-species biofilm

In mixed infections, the bacterial susceptibility differs significantly compared to monocultures of bacteria, and generally the concentrations of antibiotics required for the treatment increases drastically. For S. aureus and P. aeruginosa dual species biofilms, it has been numerously reported that P. aeruginosa decreases S. aureus susceptibility to a broad range of antibiotics, including beta-lactams, glycopeptides, aminoglycosides, macrolides, while sensitizes to quinolones via secretion of various metabolites. Here we show that S. aureus also modulates the susceptibility of P. aeruginosa to antibiotics in mixed cultures. Thus, S. aureus-P. aeruginosa consortium was characterized by tenfold increase in susceptibility to ciprofloxacin and aminoglycosides compared to monocultures. The same effect could be also achieved by the addition of cell-free culture of S. aureus to P. aeruginosa biofilm. Moreover, similar increase in antibiotics efficacy could be observed following addition of S. aureus suspension to the P. aeruginosa mature biofilm, compared to P. aeruginosa monoculture, and vice versa. These findings open promising perspectives to increase the antimicrobial treatment efficacy of the wounds infected with nosocomial pathogens by the transplantation of the skin residential microflora.

A Fluorinated Analogue of Marine Bisindole Alkaloid 2,2-Bis(6-bromo-1H-indol-3-yl)ethanamine as Potential Anti-Biofilm Agent and Antibiotic Adjuvant Against Staphylococcus aureus

Methicillin resistant Staphylococcus aureus (MRSA) infections represent a major global healthcare problem. Therapeutic options are often limited by the ability of MRSA strains to grow as biofilms on medical devices, where antibiotic persistence and resistance is positively selected, leading to recurrent and chronic implant-associated infections. One strategy to circumvent these problems is the co-administration of adjuvants, which may prolong the efficacy of antibiotic treatments, by broadening their spectrum and lowering the required dosage. The marine bisindole alkaloid 2,2-bis(6-bromo-1H-indol-3-yl)ethanamine (1) and its fluorinated analogue (2) were tested for their potential use as antibiotic adjuvants and antibiofilm agents against S. aureus CH 10850 (MRSA) and S. aureus ATCC 29213 (MSSA). Both compounds showed antimicrobial activity and bisindole 2 enabled 256-fold reduction (ΣFICs = 0.5) in the minimum inhibitory concentration (MIC) of oxacillin for the clinical MRSA strain. In addition, these molecules inhibited biofilm formation of S. aureus strains, and compound 2 showed greater eradicating activity on preformed biofilm compared to 1. None of the tested molecules exerted a viable but non-culturable cells (VBNC) inducing effect at their MIC values. Moreover, both compounds exhibited no hemolytic activity and a good stability in plasma, indicating a non-toxic profile, hence, in particular compound 2, a potential for in vivo applications to restore antibiotic treatment against MRSA infections.

Staphylococcal Biofilm Development: Structure, Regulation, and Treatment Strategies

In many natural and clinical settings, bacteria are associated with some type of biotic or abiotic surface that enables them to form biofilms, a multicellular lifestyle with bacteria embedded in an extracellular matrix. Staphylococcus aureus and Staphylococcus epidermidis, the most frequent causes of biofilm-associated infections on indwelling medical devices, can switch between an existence as single free-floating cells and multicellular biofilms. During biofilm formation, cells first attach to a surface and then multiply to form microcolonies. They subsequently produce the extracellular matrix, a hallmark of biofilm formation, which consists of polysaccharides, proteins, and extracellular DNA. After biofilm maturation into three-dimensional structures, the biofilm community undergoes a disassembly process that leads to the dissemination of staphylococcal cells. As biofilms are dynamic and complex biological systems, staphylococci have evolved a vast network of regulatory mechanisms to modify and fine-tune biofilm development upon changes in environmental conditions. Thus, biofilm formation is used as a strategy for survival and persistence in the human host and can serve as a reservoir for spreading to new infection sites. Moreover, staphylococcal biofilms provide enhanced resilience toward antibiotics and the immune response and impose remarkable therapeutic challenges in clinics worldwide. This review provides an overview and an updated perspective on staphylococcal biofilms, describing the characteristic features of biofilm formation, the structural and functional properties of the biofilm matrix, and the most important mechanisms involved in the regulation of staphylococcal biofilm formation. Finally, we highlight promising strategies and technologies, including multitargeted or combinational therapies, to eradicate staphylococcal biofilms.

Staphylococcal Biofilm Development: Structure, Regulation, and Treatment Strategies

In many natural and clinical settings, bacteria are associated with some type of biotic or abiotic surface that enables them to form biofilms, a multicellular lifestyle with bacteria embedded in an extracellular matrix. Staphylococcus aureus and Staphylococcus epidermidis, the most frequent causes of biofilm-associated infections on indwelling medical devices, can switch between an existence as single free-floating cells and multicellular biofilms. During biofilm formation, cells first attach to a surface and then multiply to form microcolonies. They subsequently produce the extracellular matrix, a hallmark of biofilm formation, which consists of polysaccharides, proteins, and extracellular DNA. After biofilm maturation into three-dimensional structures, the biofilm community undergoes a disassembly process that leads to the dissemination of staphylococcal cells. As biofilms are dynamic and complex biological systems, staphylococci have evolved a vast network of regulatory mechanisms to modify and fine-tune biofilm development upon changes in environmental conditions. Thus, biofilm formation is used as a strategy for survival and persistence in the human host and can serve as a reservoir for spreading to new infection sites. Moreover, staphylococcal biofilms provide enhanced resilience toward antibiotics and the immune response and impose remarkable therapeutic challenges in clinics worldwide. This review provides an overview and an updated perspective on staphylococcal biofilms, describing the characteristic features of biofilm formation, the structural and functional properties of the biofilm matrix, and the most important mechanisms involved in the regulation of staphylococcal biofilm formation. Finally, we highlight promising strategies and technologies, including multitargeted or combinational therapies, to eradicate staphylococcal biofilms.

Activated Polyhydroxyalkanoate Meshes Prevent Bacterial Adhesion and Biofilm Development in Regenerative Medicine Applications

Regenerative medicine has become an extremely valuable tool offering an alternative to conventional therapies for the repair and regeneration of tissues. The re-establishment of tissue and organ functions can be carried out by tissue engineering strategies or by using medical devices such as implants. However, with any material being implanted inside the human body, one of the conundrums that remains is the ease with which these materials can get contaminated by bacteria. Bacterial adhesion leads to the formation of mature, alive and complex three-dimensional biofilm structures, further infection of surrounding tissues and consequent development of complicated chronic infections. Hence, novel tissue engineering strategies delivering biofilm-targeted therapies, while at the same time allowing tissue formation are highly relevant. In this study our aim was to develop surface modified polyhydroxyalkanoate-based fiber meshes with enhanced bacterial anti-adhesive and juvenile biofilm disrupting properties for tissue regeneration purposes. Using reactive and amphiphilic star-shaped macromolecules as an additive to a polyhydroxyalkanoate spinning solution, a synthetic antimicrobial peptide, Amhelin, with strong bactericidal and anti-biofilm properties, and Dispersin B, an enzyme promoting the disruption of exopolysaccharides found in the biofilm matrix, were covalently conjugated to the fibers by addition to the solution before the spinning process. Staphylococcus epidermidis is one of the most problematic pathogens responsible for tissue-related infections. The initial antibacterial screening showed that Amhelin proved to be strongly bactericidal at 12 μg/ml and caused >50% reductions of biofilm formation at 6 μg/ml, while Dispersin B was found to disperse >70% of pre-formed biofilms at 3 μg/ml. Regarding the cytotoxicity of the agents toward L929 murine fibroblasts, a CC50 of 140 and 115 μg/ml was measured for Amhelin and Dispersin B, respectively. Optimization of the electrospinning process resulted in aligned fibers. Surface activated fibers with Amhelin and Dispersin B resulted in 83% reduction of adhered bacteria on the surface of the fibers. Additionally, the materials developed were found to be cytocompatible toward L929 murine fibroblasts. The strategy reported in this preliminary study suggests an alternative approach to prevent bacterial adhesion and, in turn biofilm formation, in materials used in regenerative medicine applications such as tissue engineering.

A Rational Designed PslG With Normal Biofilm Hydrolysis and Enhanced Resistance to Trypsin-Like Protease Digestion

A glycosyl hydrolase produced by Pseudomonas aeruginosa, PslG, has become a promising candidate for biofilm treatment because of its ability to inhibit and disperse biofilms by disrupting exopolysaccharide matrix at nanomolar concentrations. However, as a protein, PslG used for treatment may be degraded by the ubiquitous proteases (of which trypsin-like serine proteases are a major group) secreted by human cells. This would lead to an insufficient effective concentration of PslG. Here, based on the result of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and structural analysis, we generate a PslG mutant (K286A/K433S) with greatly enhanced trypsin resistance. This measure raises IC50 (the concentration of trypsin that can degrade 50% of protein in 30 min at 37°C) from 0.028 mg mL-1 of the wild-type PslG to 0.283 mg mL-1 of PslG K286A/K433S . In addition, biofilm inhibition assay shows that PslG K286A/K433S is much more efficient than wild-type PslG in the presence of trypsin. This indicates that PslG K286A/K433S is a better biofilm inhibitor than wild-type PslG in clinical use where trypsin-like proteases widely exist.

In vitro elution of amikacin and Dispersin B from a polymer hydrogel

OBJECTIVE

To characterize the in vitro elution of amikacin and Dispersin B (β-N-acetylglucosaminidase) in a degradable hydrogel.

STUDY DESIGN

In vitro, prospective study.

METHODS

Amikacin (group A; 40 mg/mL), Dispersin B (group D; 70 μg/mL), or combined amikacin and Dispersin B (group AD; 40 mg/mL and 70 μg/mL, respectively) were added to a hydrogel. Ten aliquots per group were incubated in phosphate-buffered saline that was exchanged at 1, 4, 8, 12, and 24 hours and then once daily for 10 days. Eluted amikacin and Dispersin B were quantitated by using an amikacin reagent kit and a Dispersin B enzyme-linked immunosorbent assay kit, respectively. Time point drug concentrations were compared between groups by using repeated-measures analysis of variance, and total drug elution was compared by using an area under the curve calculation.

RESULTS

Amikacin alone, Dispersin B alone, and amikacin and Dispersin B combined together underwent rapid elution in the first 24 hours, followed by a gradual decrease over 10 days. The concentration of Dispersin B eluted in group D was higher at 1 day and lower from day 5 to day 10 compared with that in group AD. The concentration of amikacin eluted in group A was higher at 1, 4, and 8 hours and on day 10 and lower on day 1 compared with that in group AD. The total elution of amikacin was greater from group AD compared with that from group A (P = .02).

CONCLUSION

Combining amikacin and Dispersin B had an affect on the total elution of amikacin but not Dispersin B.

CLINICAL SIGNIFICANCE

The combination of amikacin and Dispersin B in a degradable hydrogel could allow local treatment of complex infections without the requirement for multiple invasive procedures.

Comparative Genomics of Wild Bee and Flower Isolated Lactobacillus Reveals Potential Adaptation to the Bee Host

Symbiosis with bacteria is common across insects, resulting in adaptive host phenotypes. The recently described bacterial symbionts Lactobacillus micheneri, Lactobacillus timberlakei, and Lactobacillus quenuiae are found in wild bee pollen provisions, bee guts, and flowers but have small genomes in comparison to other lactobacilli. We sequenced, assembled, and analyzed 27 new L. micheneri clade genomes to identify their possible ecological functions in flower and bee hosts. We determined possible key functions for the L. micheneri clade by identifying genes under positive selection, balancing selection, genes gained or lost, and population structure. A host adherence factor shows signatures of positive selection, whereas other orthologous copies are variable within the L. micheneri clade. The host adherence factors serve as strong evidence that these lactobacilli are adapted to animal hosts as their targets are found in the digestive tract of insects. Next, the L. micheneri clade is adapted toward a nutrient-rich environment, corroborating observations of where L. micheneri is most abundant. Additionally, genes involved in osmotolerance, pH tolerance, temperature resistance, detoxification, and oxidative stress response show signatures of selection that allow these bacteria to thrive in pollen and nectar masses in bee nests and in the bee gut. Altogether, these findings not only suggest that the L. micheneri clade is primarily adapted to the wild bee gut but also exhibit genomic features that would be beneficial to survival in flowers.

Enhanced Clearing of Wound-Related Pathogenic Bacterial Biofilms Using Protease-Functionalized Antibiotic Nanocarriers

Biofilms are prevalent in chronic wounds and once formed are very hard to remove, which is associated with poor outcomes and high mortality rates. Biofilms are comprised of surface-attached bacteria embedded in an extracellular polymeric substance (EPS) matrix, which confers increased antibiotic resistance and host immune evasion. Therefore, disruption of this matrix is essential to tackle the biofilm-embedded bacteria. Here, we propose a novel nanotechnology to do this, based on protease-functionalized nanogel carriers of antibiotics. Such active antibiotic nanocarriers, surface coated with the protease Alcalase 2.4 L FG, "digest" their way through the biofilm EPS matrix, reach the buried bacteria, and deliver a high dose of antibiotic directly on their cell walls, which overwhelms their defenses. We demonstrated their effectiveness against six wound biofilm-forming bacteria, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis, Klebsiella pneumoniae, Escherichia coli, and Enterococcus faecalis. We confirmed a 6-fold decrease in the biofilm mass and a substantial reduction in bacterial cell density using fluorescence, atomic force, and scanning electron microscopy. Additionally, we showed that co-treatments of ciprofloxacin and Alcalase-coated Carbopol nanogels led to a 3-log reduction in viable biofilm-forming cells when compared to ciprofloxacin treatments alone. Encapsulating an equivalent concentration of ciprofloxacin into the Alcalase-coated nanogel particles boosted their antibacterial effect much further, reducing the bacterial cell viability to below detectable amounts after 6 h of treatment. The Alcalase-coated nanogel particles were noncytotoxic to human adult keratinocyte cells (HaCaT), inducing a very low apoptotic response in these cells. Overall, we demonstrated that the Alcalase-coated nanogels loaded with a cationic antibiotic elicit very strong biofilm-clearing effects against wound-associated biofilm-forming pathogenic bacteria. This nanotechnology approach has the potential to become a very powerful treatment of chronically infected wounds with biofilm-forming bacteria.