Enzymatic degradation of in vitro Staphylococcus aureus biofilms supplemented with human plasma

Powering mesoporous silica nanoparticles into bioactive nanoplatforms for antibacterial therapies: strategies and challenges

Bacterial infection has been a major threat to worldwide human health, in particular with the ever-increasing level of antimicrobial resistance. Given the complex microenvironment of bacterial infections, conventional use of antibiotics typically renders a low efficacy in infection control, thus calling for novel strategies for effective antibacterial therapies. As an excellent candidate for antibiotics delivery, mesoporous silica nanoparticles (MSNs) demonstrate unique physicochemical advantages in antibacterial therapies. Beyond the delivery capability, extensive efforts have been devoted in engineering MSNs to be bioactive to further synergize the therapeutic effect in infection control. In this review, we critically reviewed the essential properties of MSNs that benefit their antibacterial application, followed by a themed summary of strategies in manipulating MSNs into bioactive nanoplatforms for enhanced antibacterial therapies. The chemically functionalized platform, photo-synergized platform, physical antibacterial platform and targeting-directed platform are introduced in details, where the clinical translation challenges of these MSNs-based antibacterial nanoplatforms are briefly discussed afterwards. This review provides critical information of the emerging trend in turning bioinert MSNs into bioactive antibacterial agents, paving the way to inspire and translate novel MSNs-based nanotherapies in combating bacterial infection diseases.

A promising microbial α-amylase production, and purification from Bacillus cereus and its assessment as antibiofilm agent against Pseudomonas aeruginosa pathogen

BACKGROUND AND AIM

The purpose of the current study is to isolate a heavily amylase-producing bacteria of the genus Bacillus from soil samples, optimize the production of the enzyme, purify it, and evaluate its activity against biofilm-producing bacteria. A total of 12 soil samples were collected and screened for promising Bacillus species with good amylolytic activity. Isolation was done by serial dilution and plating technique and amylolytic activity was determined by starch agar plate method. Among the 12 Bacillus isolates recovered from soil samples, 7 showed positive α-amylase production. The best isolate that recorded the greatest amylolytic activity was selected for further studies. This isolate was identified by 16S rRNA sequencing as Bacillus cereus and registered under gene bank accession number OP811897. Furthermore, the α-amylase enzyme was produced by a submerged fermentation technique using best production media and partially purified by ammonium sulfate and chilled ethanol and molecular weight had been determined by SDS-PAGE gel electrophoresis. The production of α-amylase was optimized experimentally by one-factor at a time protocol and statistically by Plackett-Burman design as well as RSM CCD design. Data obtained from OFAT and CCD revealed that α-amylase activities were 1.5- and twofold respectively higher as compared to un-optimized conditions. The most significant factors had been identified and optimized by CCD design.

RESULTS

Among the eleven independent variables tested by PBD, glucose, peptone, (NH4)₂SO4, and Mg SO₄ were the most significant parameters for α-amylase production with an actual yield of 250U/ml. The best physical parameters affecting the enzyme production were incubation time at 35 °C, and pH 5.5 for 48 h. The partially purified enzyme with 60% ammonium sulphate saturation with 1.38- fold purification showed good stability characteristics at a storage temperature of 4 °C and pH up to 8.5 for 21 days. Antibiofilm activity of purified α-amylase was determined against Pseudomonas aeruginosa (ATCC 35659) by spectrophotometric analysis and CLSM microscopic analysis. Results demonstrated biofilm inhibition by 84% of the formed Pseudomonas biofilm using a microtiter plate assay and thickness inhibition activity by 83% with live/Dead cells percentage of 17%/83% using CLSM protocol.

CONCLUSIONS

A highly stable purified α-amylase from B. cereus showed promising antibiofilm activity against one of the clinically important biofilm-forming MDR organisms that could be used as a cost-effective tool in pharmaceutical industries.

Polysaccharides' Structures and Functions in Biofilm Architecture of Antimicrobial-Resistant (AMR) Pathogens

Bacteria and fungi have developed resistance to the existing therapies such as antibiotics and antifungal drugs, and multiple mechanisms are mediating this resistance. Among these, the formation of an extracellular matrix embedding different bacterial cells, called biofilm, is an effective strategy through which bacterial and fungal cells are establishing a relationship in a unique environment. The biofilm provides them the possibility to transfer genes conferring resistance, to prevent them from desiccation and to impede the penetration of antibiotics or antifungal drugs. Biofilms are formed of several constituents including extracellular DNA, proteins and polysaccharides. Depending on the bacteria, different polysaccharides form the biofilm matrix in different microorganisms, some of them involved in the first stage of cells' attachment to surfaces and to each other, and some responsible for giving the biofilm structure resistance and stability. In this review, we describe the structure and the role of different polysaccharides in bacterial and fungal biofilms, we revise the analytical methods to characterize them quantitatively and qualitatively and finally we provide an overview of potential new antimicrobial therapies able to inhibit biofilm formation by targeting exopolysaccharides.

Lysostaphin: Engineering and Potentiation toward Better Applications

Lysostaphin is a potent bacteriolytic enzyme with endopeptidase activity against the common pathogen Staphylococcus aureus. By digesting the pentaglycine crossbridge in the cell wall peptidoglycan of S. aureus including the methicillin-resistant strains, lysostaphin initiates rapid lysis of planktonic and sessile cells (biofilms) and has great potential for use in agriculture, food industries, and pharmaceutical industries. In the past few decades, there have been tremendous efforts in potentiating lysostaphin for better applications in these fields, including engineering of the enzyme for higher potency and lower immunogenicity with longer-lasting effects, formulation and immobilization of the enzyme for higher stability and better durability, and recombinant expression for low-cost industrial production and in situ biocontrol. These achievements are extensively reviewed in this article focusing on applications in disease control, food preservation, surface decontamination, and pathogen detection. In addition, some basic properties of lysostaphin that have been controversial and only elucidated recently are summarized, including the substrate-binding properties, the number of zinc-binding sites, the substrate range, and the cleavage site in the pentaglycine crossbridge. Resistance to lysostaphin is also highlighted with a focus on various mechanisms. This article is concluded with a discussion on the limitations and future perspectives for the actual applications of lysostaphin.

The Innate Immune Protein Calprotectin Interacts With and Encases Biofilm Communities of Pseudomonas aeruginosa and Staphylococcus aureus

Calprotectin is a transition metal chelating protein of the innate immune response known to exert nutritional immunity upon microbial infection. It is abundantly released during inflammation and is therefore found at sites occupied by pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus. The metal limitation induced by this protein has previously been shown to mediate P. aeruginosa and S. aureus co-culture. In addition to the transition metal sequestration role of calprotectin, it has also been shown to have metal-independent antimicrobial activity via direct cell contact. Therefore, we sought to assess the impact of this protein on the biofilm architecture of P. aeruginosa and S. aureus in monomicrobial and polymicrobial culture. The experiments described in this report reveal novel aspects of calprotectin's interaction with biofilm communities of P. aeruginosa and S. aureus discovered using scanning electron microscopy and confocal laser scanning microscopy. Our results indicate that calprotectin can interact with microbial cells by stimulating encapsulation in mesh-like structures. This physical interaction leads to compositional changes in the biofilm extracellular polymeric substance (EPS) in both P. aeruginosa and S. aureus.

Evaluation of antibiofilm potential of four-domain α-amylase from Streptomyces griseus against exopolysaccharides (EPS) of bacterial pathogens using Danio rerio

Biofilm formation is a major issue in healthcare settings as 75% of nosocomial infection arises due to biofilm residing bacteria. Exopolysaccharides (EPS), a key component of the biofilm matrix, contribute to the persistence of cells in a complex milieu and defends greatly from exogenous stress and demolition. It has been shown to be vital for biofilm scaffold and pathogenic features. The present study was aimed to investigate the effectiveness of four domain-containing α-amylase from Streptomyces griseus (SGAmy) in disrupting the EPS of multidrug-resistant bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. In vitro analysis of preformed biofilm unveiled the antibiofilm efficacy of SGAmy against MRSA (85%, p < 0.05) and P. aeruginosa (82%, p < 0.05). The total carbohydrate content in the EPS matrix of MRSA and P. aeruginosa was significantly reduced to 71.75% (p < 0.01) and 74.09% (p < 0.01), respectively. The findings inferred from in vitro analysis were further corroborated through in vivo studies using an experimental model organism, Danio rerio. Remarkably, the survival rate was extended to 88.8% (p < 0.05) and 74.2% (p < 0.05) in MRSA and P. aeruginosa infected fishes, respectively. An examination of gills, kidneys, and intestines of D. rerio organs depicted the reduced level of microbial colonization in SGAmy-treated cohorts and these findings were congruent with bacterial enumeration results.

The Production of Streptomyces W-5B Extract for Antibiofilm against Methicillin-resistant Staphylococcus aureus

The ability of Methicillin-resistant Staphylococcus aureus (MRSA) to form biofilms is one of the triggering factors for the emergence of MRSA resistance to antibiotics. Streptomyces W-5B has shown potency as an antibacterial producer against MRSA. However, the production of microbial bioactive compounds is strongly affected by the source of nutrients in the fermentation medium. Therefore, the objective of this study was to determine the optimal sources of carbon and nitrogen for the production of bioactive compounds with antibiofilm activities. The research method included cultivating Streptomyces W-5B, extract production, and variation of carbon (glucose, sucrose, starch) and nitrogen (casein, peptone, urea) sources for fermentation medium. Antibiofilm activities were measured based on inhibition of biofilm formation and biofilm degradation tests using the microtiter plate method with a crystal violet stain. The results showed that the highest inhibition of biofilm formation was 68.206 ± 1.750% after 12 days of incubation in a fermentation medium containing sucrose and urea. Meanwhile, the highest biofilm degradation was 73.023 ± 1.972% after nine days of incubation on a fermentation medium containing starch and urea. These findings indicated that Streptomyces W-5B has the potency to produce antibiofilm extract against MRSA.

Milieu matters: An in vitro wound milieu to recapitulate key features of, and probe new insights into, mixed-species bacterial biofilms

Bacterial biofilms are a major cause of delayed wound healing. Consequently, the study of wound biofilms, particularly in host-relevant conditions, has gained importance. Most in vitro studies employ refined laboratory media to study biofilms, representing conditions that are not relevant to the infection state. To mimic the wound milieu, in vitro biofilm studies often incorporate serum or plasma in growth conditions, or employ clot or matrix-based biofilm models. While incorporating serum or plasma alone is a minimalistic approach, the more complex in vitro wound models are technically demanding, and poorly compatible with standard biofilm assays. Based on previous reports of clinical wound fluid composition, we have developed an in vitro wound milieu (IVWM) that includes, in addition to serum (to recapitulate wound fluid), matrix elements and biochemical factors. With Luria-Bertani broth and Fetal Bovine Serum (FBS) for comparison, the IVWM was used to study planktonic growth, biofilm features, and interspecies interactions, of common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. We demonstrate that the IVWM recapitulates widely reported in vivo biofilm features such as biomass formation, metabolic activity, increased antibiotic tolerance, 3D structure, and interspecies interactions for monospecies and mixed-species biofilms. Further, the IVWM is simple to formulate, uses laboratory-grade components, and is compatible with standard biofilm assays. Given this, it holds potential as a tractable approach to study wound biofilms under host-relevant conditions.

Increased biofilm formation by Staphylococcus aureus clinical isolates on surfaces covered with plasma proteins

Introduction. Biofilm formation is a major virulence factor associated with Staphylococcus aureus infections. However, the influence of plasma proteins on biofilm formation of clinical isolates in vitro remains unclear.Hypotheses. We hypothesized that coating surfaces with plasma proteins might induce biofilm formation by S. aureus of different clonal lineages.Aim. To evaluate biofilm production by clinical S. aureus isolates of different clonal lineages isolated in Rio de Janeiro hospitals and investigated the presence of biofilm-associated genes.Methodology. This study assessed biofilm production of 60 S. aureus isolates in polystyrene microtitre plates with and without fibrinogen or fibronectin. The biochemical composition of the biofilm matrices was determined and the biofilm formation on fibrinogen-coated surfaces was also evaluated by confocal laser scanning microscopy. The presence of biofilm-related genes was detected by PCR, and the typing and functionality of agr operon was also evaluated.Results. Most of the isolates (45 %) were weak biofilm producers or non-producers. However, most of them presented a significant increase in biofilm production on plates covered with plasma proteins. There was no significant difference in biofilm formation between methicillin-resistant and -susceptible S. aureus isolates, or between different clonal lineages, except for ST30-IV (weak producers) and ST239-III (strong producers). The fnbB gene was associated with higher biofilm production.Conclusion. An increase in biofilm production in the presence of plasma proteins highlights the importance of investigating biofilm formation by S. aureus clinical isolates under different conditions since this virulence factor contributes to persistent infections and increased resistance to antimicrobials.

Amylases: Biofilm Inducer or Biofilm Inhibitor?

Biofilm is a syntrophic association of sessile groups of microbial cells that adhere to biotic and abiotic surfaces with the help of pili and extracellular polymeric substances (EPS). EPSs also prevent penetration of antimicrobials/antibiotics into the sessile groups of cells. Hence, methods and agents to avoid or remove biofilms are urgently needed. Enzymes play important roles in the removal of biofilm in natural environments and may be promising agents for this purpose. As the major component of the EPS is polysaccharide, amylase has inhibited EPS by preventing the adherence of the microbial cells, thus making amylase a suitable antimicrobial agent. On the other hand, salivary amylase binds to amylase-binding protein of plaque-forming Streptococci and initiates the formation of biofilm. This review investigates the contradictory actions and microbe-associated genes of amylases, with emphasis on their structural and functional characteristics.

Enzyme-Functionalized Mesoporous Silica Nanoparticles to Target Staphylococcus aureus and Disperse Biofilms

BACKGROUND

Staphylococcus aureus biofilms pose a unique challenge in healthcare due to their tolerance to a wide range of antimicrobial agents. The high cost and lengthy timeline to develop novel therapeutic agents have pushed researchers to investigate the use of nanomaterials to deliver antibiofilm agents and target biofilm infections more efficiently. Previous studies have concentrated on improving the efficacy of antibiotics by deploying nanoparticles as nanocarriers. However, the dispersal of the extracellular polymeric substance (EPS) matrix in biofilm-associated infections is also critical to the development of novel nanoparticle-based therapies.

METHODS

This study evaluated the efficacy of enzyme-functionalized mesoporous silica nanoparticles (MSNs) against methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) biofilms. MSNs were functionalized with the enzyme lysostaphin, which causes cell lysis of S. aureus bacteria. This was combined with two other enzyme functionalized MSNs, serrapeptase and DNase I which will degrade protein and eDNA in the EPS matrix, to enhance eradication of the biofilm. Cell viability after treatment with enzyme-functionalized MSNs was assessed using a MTT assay and CLSM, while crystal violet staining was used to assess EPS removal.

RESULTS

The efficacy of all three enzymes against S. aureus cells and biofilms was significantly improved when they were immobilized onto MSNs. Treatment efficacy was further enhanced when the three enzymes were used in combination against both MRSA and MSSA. Regardless of biofilm maturity (24 or 48 h), near-complete dispersal and killing of MRSA biofilms were observed after treatment with the enzyme-functionalized MSNs. Disruption of mature MSSA biofilms with a polysaccharide EPS was less efficient, but cell viability was significantly reduced.

CONCLUSION

The combination of these three enzymes and their functionalization onto nanoparticles might extend the therapeutic options for the treatment of S. aureus infections, particularly those with a biofilm component.

Antibiofilm Activity of α-Amylase from Bacillus subtilis and Prediction of the Optimized Conditions for Biofilm Removal by Response Surface Methodology (RSM) and Artificial Neural Network (ANN)

α-amylase is known to have antibiofilm activity against biofilms of both Gram positive and Gram-negative bacterial strains. Partially purified α-amylase from Bacillus subtilis was found to have inhibit biofilm formed by P. aeruginosa and S. aureus. The spectrophotometric and microscopic studies revealed that the antibiofilm efficacy of the working strain is greater than commercially purchased α-amylase. Response surface methodology (RSM) and artificial neural network (ANN) help to predict the optimum conditions [pH 8, treatment time 6 h and enzyme concentration (200 µg/mL)] for maximum biofilm eradication. This was confirmed by several in vitro experiments. Molecular docking interactions of α-amylase with the extracellular polymeric substances (EPS) of both P. aeruginosa and S. aureus indicate towards the existence of an efficient energy driven spontaneous process. Thus, this study highlights a combination of experimental and computational approach showing the naturally extracted α-amylase from B. subtilis having the potency of removing the biofilms of harmful bacterial strains involved in causing various nosocomial infections.

Efficient Biofilms Eradication by Enzymatic-Cocktail of Pancreatic Protease Type-I and Bacterial α-Amylase

Removal of biofilms is extremely pivotal in environmental and medicinal fields. Therefore, reporting the new-enzymes and their combinations for dispersal of infectious biofilms can be extremely critical. Herein, for the first time, we accessed the enzyme "protease from bovine pancreas type-I (PtI)" for anti-biofilm properties. We further investigated the anti-biofilm potential of PtI in combination with α-amylase from Bacillus sp. (αA). PtI showed a very significant biofilm inhibition effect (86.5%, 88.4%, and 67%) and biofilm prevention effect (66%, 64%, and 70%), against the E. coli, S. aureus, and MRSA, respectively. However, the new enzyme combination (Ec-PtI+αA) exhibited biofilm inhibition effect (78%, 90%, and 93%) and a biofilm prevention effect (44%, 51%, and 77%) against E. coli, S. aureus, and MRSA, respectively. The studied enzymes were found not to be anti-bacterial against the E. coli, S. aureus, and MRSA. In summary, the PtI exhibited significant anti-biofilm effects against S. aureus, MRSA, and E. coli. Ec-PtI+αA exhibited enhancement of the anti-biofilm effects against S. aureus and MRSA biofilms. Therefore, this study revealed that this Ec-PtI+αA enzymatic system can be extremely vital for the treatment of biofilm complications resulting from E. coli, S. aureus, and MRSA.

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.

Nanomaterials for Treating Bacterial Biofilms on Implantable Medical Devices

Bacterial biofilms are involved in most device-associated infections and remain a challenge for modern medicine. One major approach to addressing this problem is to prevent the formation of biofilms using novel antimicrobial materials, device surface modification or local drug delivery; however, successful preventive measures are still extremely limited. The other approach is concerned with treating biofilms that have already formed on the devices; this approach is the focus of our manuscript. Treating biofilms associated with medical devices has unique challenges due to the biofilm's extracellular polymer substance (EPS) and the biofilm bacteria's resistance to most conventional antimicrobial agents. The treatment is further complicated by the fact that the treatment must be suitable for applying on devices surrounded by host tissue in many cases. Nanomaterials have been extensively investigated for preventing biofilm formation on medical devices, yet their applications in treating bacterial biofilm remains to be further investigated due to the fact that treating the biofilm bacteria and destroying the EPS are much more challenging than preventing adhesion of planktonic bacteria or inhibiting their surface colonization. In this highly focused review, we examined only studies that demonstrated successful EPS destruction and biofilm bacteria killing and provided in-depth description of the nanomaterials and the biofilm eradication efficacy, followed by discussion of key issues in this topic and suggestion for future development.

Detection of Heavy Metal Tolerance among different MLSB Resistance Phenotypes of Methicillin-Resistant S. aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) strains are widespread globally. Besides their virulence factors, the co-occurrence of antimicrobial and metal resistance has been reported. This study was designed to evaluate the antibiotic resistance and resistance phenotypes, investigate the occurrence of virulence factors, and detect heavy metal tolerance among MRSA strains. Antibiogram profiling was done as recommended by CLSI instructions. Resistance phenotypes were detected by D test, followed by characterization of enzymatic activities and biofilm formation assay. Antibacterial activity of different heavy metals was tested, and predictable synergistic assay was performed. Among MRSA strains collected, high resistance to ampicillin and amoxicillin/clavulanate (100%) and high susceptibility to clindamycin (70%) were obtained. Resistance phenotypes were detected as S, constitutive MLSB, inducible MLSB, and MS by percentages of 10%, 30%, 30% and 30% respectively. Virulence factors like lipolytic (50%) and hemolytic (70%) activity, and biofilm formation ability (100%) were detected. High resistance towards potassium and magnesium was observed. MTC of 500 ppm was detected for all isolates in case of cobalt and iron. In case of zinc and copper, MTC was detected as 500 ppm except for one isolate which was highly resistant, and 500 ppm for all isolates except for two isolates which were highly sensitive respectively. Magnesium in different concentrations (500 and 2000 ppm) showed synergistic activity with erythromycin and clindamycin. Results reveal high heavy metal tolerance among antibiotic resistant MRSA strains, in addition to the presence of virulence factors. Upcoming studies must be focused on the combination of sub-inhibitory concentration of different heavy metals with the available antibiotics.

Utilizing glycoside hydrolases to improve the quantitation and visualization of biofilm bacteria

The complexity of microbial biofilms offers several challenges to the use of traditional means of microbial research. In particular, it can be difficult to calculate accurate numbers of biofilm bacteria, because even after thorough homogenization or sonication, small pieces of the biofilm remain, which contain numerous bacterial cells and result in inaccurately low colony forming units (CFU). In addition, imaging of infected tissue ex vivo often results in a disparity between the CFU and the number of bacterial cells observed under the microscope. We hypothesized that this phenomenon is due to the biofilm extracellular polymeric substance decreasing the accessibility of stains and antibodies to the embedded bacterial cells. In this study, we describe incorporating EPS-degrading glycoside hydrolases for CFU determination to obtain a more accurate estimation of the viable cells and for immunohistochemistry to disrupt the biofilm matrix and increase primary antibody binding to the bacterial cells.

Targeting Biofilms Therapy: Current Research Strategies and Development Hurdles

Biofilms are aggregate of microorganisms in which cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS) and adhere to each other and/or to a surface. The development of biofilm affords pathogens significantly increased tolerances to antibiotics and antimicrobials. Up to 80% of human bacterial infections are biofilm-associated. Dispersal of biofilms can turn microbial cells into their more vulnerable planktonic phenotype and improve the therapeutic effect of antimicrobials. In this review, we focus on multiple therapeutic strategies that are currently being developed to target important structural and functional characteristics and drug resistance mechanisms of biofilms. We thoroughly discuss the current biofilm targeting strategies from four major aspects—targeting EPS, dispersal molecules, targeting quorum sensing, and targeting dormant cells. We explain each aspect with examples and discuss the main hurdles in the development of biofilm dispersal agents in order to provide a rationale for multi-targeted therapy strategies that target the complicated biofilms. Biofilm dispersal is a promising research direction to treat biofilm-associated infections in the future, and more in vivo experiments should be performed to ensure the efficacy of these therapeutic agents before being used in clinic.

van Leeuwen W, Jabalameli F. Combinatorial effects of antibiotics and enzymes against dual-species Staphylococcus aureus and Pseudomonas aeruginosa biofilms in the wound-like medium

Bacterial biofilms are one of the major issues in the treatment of chronic infections such as chronic wounds, where biofilms are typically polymicrobial. The synergy between species can occur during most polymicrobial infections, where antimicrobial resistance enhances as a result. Furthermore, self-produced extracellular polymeric substance (EPS) in biofilms results in a high tolerance to antibiotics that complicates wound healing. Since most antibiotics fail to remove biofilms in chronic infections, new therapeutic modalities may be required. Disruption of EPS is one of the effective approaches for biofilm eradication. Therefore, degradation of EPS using enzymes may result in improved chronic wounds healing. In the current study, we investigated the efficacy of trypsin, β-glucosidase, and DNase I enzymes on the degradation of dual-species biofilms of Pseudomonas aeruginosa and Staphylococcus aureus in a wound-like medium. These species are the two most common bacteria associated with biofilm formation in chronic wounds. Moreover, the reduction of minimum biofilm eradication concentration (MBEC) of meropenem and amikacin was evaluated when combined with enzymes. The minimum effective concentrations of trypsin, β-glucosidase, and DNase I enzymes to degrade biofilms were 1 μg/ml, 8 U/ml, and 150 U/ml, respectively. Combination of 0.15 μg/ml trypsin and 50 U/ml DNase I had a significant effect on S. aureus-P. aeruginosa biofilms which resulted in the dispersal and dissolution of all biofilms. In the presence of the enzymatic mixture, MBECs of antibiotics showed a significant decrease (p < 0.05), at least 2.5 fold. We found that trypsin/DNase I mixture can be used as an anti-biofilm agent against dual-species biofilms of S. aureus-P. aeruginosa.

Innovative Strategies Toward the Disassembly of the EPS Matrix in Bacterial Biofilms

Bacterial biofilms represent a major concern at a worldwide level due to the high demand for implantable medical devices and the rising numbers of bacterial resistance. The complex structure of the extracellular polymeric substances (EPS) matrix plays a major role in this phenomenon, since it protects bacteria from antibiotics, avoiding drug penetration at bactericidal concentrations. Besides, this structure promotes bacterial cells to adopt a dormant lifestyle, becoming less susceptible to antibacterial agents. Currently, the available treatment for biofilm-related infections consists in the administration of conventional antibiotics at high doses for a long-term period. However, this treatment lacks efficiency against mature biofilms and for implant-associated biofilms it may be necessary to remove the medical device. Thus, biofilm-related infections represent an economical burden for the healthcare systems. New strategies focusing on the matrix are being highlighted as alternative therapies to eradicate biofilms. Here, we outline reported matrix disruptive agents, nanocarriers, and technologies, such as application of magnetic fields, photodynamic therapy, and ultrasounds, that have been under investigation to disrupt the EPS matrix of clinically relevant bacterial biofilms. In an ideal therapy, a synergistic effect between antibiotics and the explored innovated strategies is aimed to completely eradicate biofilms and avoid antimicrobial resistance phenomena.

Ultrasound-mediated therapies for the treatment of biofilms in chronic wounds: a review of present knowledge

Bacterial biofilms are an ever-growing concern for public health, featuring both inherited genetic resistance and a conferred innate tolerance to traditional antibiotic therapies. Consequently, there is a growing interest in novel methods of drug delivery, in order to increase the efficacy of antimicrobial agents. One such method is the use of acoustically activated microbubbles, which undergo volumetric oscillations and collapse upon exposure to an ultrasound field. This facilitates physical perturbation of the biofilm and provides the means to control drug delivery both temporally and spatially. In line with current literature in this area, this review offers a rounded argument for why ultrasound-responsive agents could be an integral part of advancing wound care. To achieve this, we will outline the development and clinical significance of biofilms in the context of chronic infections. We will then discuss current practices used in combating biofilms in chronic wounds and then critically evaluate the use of acoustically activated gas microbubbles as an emerging treatment modality. Moreover, we will introduce the novel concept of microbubbles carrying biologically active gases that may facilitate biofilm dispersal.

Bacterial biopolymers: from pathogenesis to advanced materials

Bacteria are prime cell factories that can efficiently convert carbon and nitrogen sources into a large diversity of intracellular and extracellular biopolymers, such as polysaccharides, polyamides, polyesters, polyphosphates, extracellular DNA and proteinaceous components. Bacterial polymers have important roles in pathogenicity, and their varied chemical and material properties make them suitable for medical and industrial applications. The same biopolymers when produced by pathogenic bacteria function as major virulence factors, whereas when they are produced by non-pathogenic bacteria, they become food ingredients or biomaterials. Interdisciplinary research has shed light on the molecular mechanisms of bacterial polymer synthesis, identified new targets for antibacterial drugs and informed synthetic biology approaches to design and manufacture innovative materials. This Review summarizes the role of bacterial polymers in pathogenesis, their synthesis and their material properties as well as approaches to design cell factories for production of tailor-made bio-based materials suitable for high-value applications.

The Synergy of Ciprofloxacin and Carvedilol against Staphylococcus aureus-Prospects of a New Treatment Strategy?

Staphylococcus aureus infections are common and difficult to treat. The increasing number of drug-resistant staphylococcal infections has created the need to develop new strategies for the treatment of these infections. The synergistic antimicrobial activity of different pharmaceuticals seems to be an interesting alternative. The aim of this study was to assess the synergistic activity of ciprofloxacin and carvedilol against S. aureus strains. The antibacterial potential of ciprofloxacin and carvedilol was evaluated according to the CLSI guidelines. The calcium content in S. aureus cells was measured using flow cytometry and atomic absorption spectroscopy. Moreover, confocal and scanning electron microscopy were used to determine the mechanism of antibacterial synergy of ciprofloxacin and carvedilol. The antibacterial effect of ciprofloxacin was higher in the presence of carvedilol than in S. aureus cultures containing the antibiotic only. A significant increase in S. aureus membrane permeability was also observed. The simultaneous administration of the tested compounds caused damage to S. aureus cells visualized by SEM. Enhancement of the antimicrobial action of ciprofloxacin by carvedilol was correlated with an increase in free calcium content in S. aureus cells, morphological changes to the cells, and a reduction in the ability to form bacterial aggregates.

Análise da “1a Recomendação Brasileira para o Gerenciamento do Biofilme em Feridas Crônicas e Complexas”

Objetivos: Analisar criticamente a “1ª Recomendação brasileira para o gerenciamento de biofilme em feridas crônicas e complexas”. Método: Realizou-se revisão da literatura atual às informações nele contidas. Resultados: Observou-se que a publicação carece de metodologia compatível com o título, existem lacunas nas recomendações quanto à classificação das evidências e com ausência de fundamentação a partir de importantes consensos internacionais para o tratamento das feridas complexas com suspeita de biofilme, publicados nos últimos três anos. Conclusão: Conclui-se que o manuscrito não deve ser usado como guia de recomendações clínicas, mas como revisão bibliográfica sobre o tema.

Analysis of “1st Brazilian Recommendation for Biofilm Management in Chronic and Complex Wounds”

Objectives: Analyze critically the “1st Brazilian Recommendation for Biofilm Management in Chronic and Complex Wounds” (from Portuguese, “1a Recomendação Brasileira para o Gerenciamento de Biofilme em Feridas Crônicas e Complexas”). Method: Reviewing information contained in said document according to current literature. Results: The publication was showed to lack methodology compatible with its title; gaps in the recommendations were perceived regarding evidence classification, as well as an absence of grounding from important international consensus, published in the last three years, about treatment of complex wounds with suspected biofilm. Conclusion: The document was concluded to be inadequate for use as a clinical guideline, being considered only a bibliographic review about the theme.

Matrix metalloprotease-1 inhibits and disrupts Enterococcus faecalis biofilms

Enterococcus faecalis is a major opportunistic pathogen that readily forms protective biofilms leading to chronic infections. Biofilms protect bacteria from detergent solutions, antimicrobial agents, environmental stress, and effectively make bacteria 10 to 1000-fold more resistant to antibiotic treatment. Extracellular proteins and polysaccharides are primary components of biofilms and play a key role in cell survival, microbial persistence, cellular interaction, and maturation of E. faecalis biofilms. Degradation of biofilm components by mammalian proteases is an effective antibiofilm strategy because proteases are known to degrade bacterial proteins leading to bacterial cell lysis and growth inhibition. Here, we show that human matrix metalloprotease-1 inhibits and disrupts E. faecalis biofilms. MMPs are cell-secreted zinc- and calcium-dependent proteases that degrade and regulate various structural components of the extracellular matrix. Human MMP1 is known to degrade type-1 collagen and can also cleave a wide range of substrates. We found that recombinant human MMP1 significantly inhibited and disrupted biofilms of vancomycin sensitive and vancomycin resistant E. faecalis strains. The mechanism of antibiofilm activity is speculated to be linked with bacterial growth inhibition and degradation of biofilm matrix proteins by MMP1. These findings suggest that human MMP1 can potentially be used as a potent antibiofilm agent against E. faecalis biofilms.

Matrix metalloprotease-1 inhibits and disrupts Enterococcus faecalis biofilms

Enterococcus faecalis is a major opportunistic pathogen that readily forms protective biofilms leading to chronic infections. Biofilms protect bacteria from detergent solutions, antimicrobial agents, environmental stress, and effectively make bacteria 10 to 1000-fold more resistant to antibiotic treatment. Extracellular proteins and polysaccharides are primary components of biofilms and play a key role in cell survival, microbial persistence, cellular interaction, and maturation of E. faecalis biofilms. Degradation of biofilm components by mammalian proteases is an effective antibiofilm strategy because proteases are known to degrade bacterial proteins leading to bacterial cell lysis and growth inhibition. Here, we show that human matrix metalloprotease-1 inhibits and disrupts E. faecalis biofilms. MMPs are cell-secreted zinc- and calcium-dependent proteases that degrade and regulate various structural components of the extracellular matrix. Human MMP1 is known to degrade type-1 collagen and can also cleave a wide range of substrates. We found that recombinant human MMP1 significantly inhibited and disrupted biofilms of vancomycin sensitive and vancomycin resistant E. faecalis strains. The mechanism of antibiofilm activity is speculated to be linked with bacterial growth inhibition and degradation of biofilm matrix proteins by MMP1. These findings suggest that human MMP1 can potentially be used as a potent antibiofilm agent against E. faecalis biofilms.

Topical adjuvants incompletely remove adherent Staphylococcus aureus from implant materials

Adjuvant treatments including Betadine, Dakin's solution (sodium hypochlorite), or hydrogen peroxide (H₂ O₂ ) have been attempted to eradicate prosthetic joint infection caused by biofilm or intracellular bacteria. The purpose of this study was to evaluate the in vitro abilities of chemical adjuvants to decrease Staphylococcus aureus (S. aureus) biofilm presence on orthopaedic implant grade materials, including titanium, stainless steel, and cobalt chrome. S. aureus biofilms were grown for 48 h and evaluated for baseline colony forming units/centimeter squared (CFU/cm² ) and compared to treatments with Betadine, Dakin's solution, H₂ O₂ , or 1% chlorine dioxide (ClO₂ ). Control discs (n = 18) across all metals had an average of 4.2 × 10⁷ CFU/cm² . All treatments had statistically significant reductions in CFU/cm² when compared to respective control discs (p < 0.05). For all metals combined, the most efficacious treatments were Betadine and H₂ O₂ , with an average 98% and 97% CFU/cm² reduction, respectively. There were no significant differences between reductions seen with Betadine and H₂ O₂ , but both groups had statistically greater reductions than Dakin's solution and ClO₂ . There was no change in antibiotic resistance patterns after treatment. Analysis of S. aureus biofilms demonstrated a statistically significant reduction in biofilm after a five-minute treatment with the modalities, with an average two log reduction in CFU/cm² . Statement of clinical significance: While statistically significant reductions in CFU/cm² were accomplished with chemical adjuvant treatments, the overall concentration of bacteria never fell below 10⁵ CFU/cm² , leading to questionable clinical significance. Further techniques to eradicate biofilm should be investigated. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1599-1604, 2018.

Current therapies in treatment and prevention of fracture wound biofilms: why a multifaceted approach is essential for resolving persistent infections

Traumatic orthopedic injuries, particularly extremity wounds, are a significant cause of morbidity. Despite prophylactic antibiotic treatment and surgical intervention, persistent infectious complications can and do occur. Persistent bacterial infections are often caused by biofilms, communities of antibiotic tolerant bacteria encased within a matrix. The structural and metabolic differences in this mode of growth make treatment difficult. Herein, we describe both established and novel, experimental treatments targeted at various stages of wound healing that are specifically aimed at reducing and eliminating biofilm bacteria. Importantly, the highly tolerant nature of these bacterial communities suggests that most singular approaches could be circumvented and a multifaceted, combinatorial approach will be the most effective strategy for treating these complicated infections.

Secretome of Intestinal Bacilli: A Natural Guard against Pathologies

Current studies of human gut microbiome usually do not consider the special functional role of transient microbiota, although some of its members remain in the host for a long time and produce broad spectrum of biologically active substances. Getting into the gastrointestinal tract (GIT) with food, water and probiotic preparations, two representatives of Bacilli class, genera Bacillus and Lactobacillus, colonize epithelium blurring the boundaries between resident and transient microbiota. Despite their minor proportion in the microbiome composition, these bacteria can significantly affect both the intestinal microbiota and the entire body thanks to a wide range of secreted compounds. Recently, insufficiency and limitations of pure genome-based analysis of gut microbiota became known. Thus, the need for intense functional studies is evident. This review aims to characterize the Bacillus and Lactobacillus in GIT, as well as the functional roles of the components released by these members of microbial intestinal community. Complex of their secreted compounds is referred by us as the "bacillary secretome." The composition of the bacillary secretome, its biological effects in GIT and role in counteraction to infectious diseases and oncological pathologies in human organism is the subject of the review.

Approaches to Dispersing Medical Biofilms

Biofilm-associated infections pose a complex problem to the medical community, in that residence within the protection of a biofilm affords pathogens greatly increased tolerances to antibiotics and antimicrobials, as well as protection from the host immune response. This results in highly recalcitrant, chronic infections and high rates of morbidity and mortality. Since as much as 80% of human bacterial infections are biofilm-associated, many researchers have begun investigating therapies that specifically target the biofilm architecture, thereby dispersing the microbial cells into their more vulnerable, planktonic mode of life. This review addresses the current state of research into medical biofilm dispersal. We focus on three major classes of dispersal agents: enzymes (including proteases, deoxyribonucleases, and glycoside hydrolases), antibiofilm peptides, and dispersal molecules (including dispersal signals, anti-matrix molecules, and sequestration molecules). Throughout our discussion, we provide detailed lists and summaries of some of the most prominent and extensively researched dispersal agents that have shown promise against the biofilms of clinically relevant pathogens, and we catalog which specific microorganisms they have been shown to be effective against. Lastly, we discuss some of the main hurdles to development of biofilm dispersal agents, and contemplate what needs to be done to overcome them.

Glycoside Hydrolases Degrade Polymicrobial Bacterial Biofilms in Wounds

The persistent nature of chronic wounds leaves them highly susceptible to invasion by a variety of pathogens that have the ability to construct an extracellular polymeric substance (EPS). This EPS makes the bacterial population, or biofilm, up to 1,000-fold more antibiotic tolerant than planktonic cells and makes wound healing extremely difficult. Thus, compounds which have the ability to degrade biofilms, but not host tissue components, are highly sought after for clinical applications. In this study, we examined the efficacy of two glycoside hydrolases, α-amylase and cellulase, which break down complex polysaccharides, to effectively disrupt Staphylococcus aureus and Pseudomonas aeruginosa monoculture and coculture biofilms. We hypothesized that glycoside hydrolase therapy would significantly reduce EPS biomass and convert bacteria to their planktonic state, leaving them more susceptible to conventional antimicrobials. Treatment of S. aureus and P. aeruginosa biofilms, grown in vitro and in vivo, with solutions of α-amylase and cellulase resulted in significant reductions in biomass, dissolution of the biofilm, and an increase in the effectiveness of subsequent antibiotic treatments. These data suggest that glycoside hydrolase therapy represents a potential safe, effective, and new avenue of treatment for biofilm-related infections.