The cidA murein hydrolase regulator contributes to DNA release and biofilm development in Staphylococcus aureus

Tannin extracted from Penthorum chinense Pursh, a potential drug with antimicrobial and antibiofilm effects against methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is an opportunistic pathogen. Due to the widespread use and abuse of antibiotics, various drug-resistant strains of S. aureus have emerged, with methicillin-resistant Staphylococcus aureus (MRSA) being the most prevalent. Bacterial biofilm is a significant contributor to bacterial infection and drug resistance. Consequently, bacterial biofilm formation has emerged as a therapeutic strategy. In this study, the chemical constituents, antimicrobial and antibiofilm properties of tannins isolated from Penthorum chinense Pursh (TPCP) were investigated. In vitro, TPCP exhibited antimicrobial properties. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) for methicillin-sensitive Staphylococcus aureus (MSSA) and MRSA were 156.25 and 312.5 μg/mL, and 312.5 and 625 μg/mL, respectively. According to the growth curves, TPCP significantly inhibited the growth of MSSA and MRSA. The results of the crystal violet biofilm assay in conjunction with confocal laser scanning and scanning electron microscopy demonstrated that TPCP destroyed preformed MSSA and MRSA biofilms. TPCP significantly decreased the secretion of exopolysaccharides and extracellular DNA. Subsequently, the mechanism was investigated using RT-PCR. Examining the expression of icaA, cidA, sigB, agrA, and sarA genes in MRSA, we discovered that TPCP inhibited biofilm formation by affecting the quorum-sensing system in bacteria. Our study demonstrates that TPCP exerts antibacterial effects by disrupting the formation of bacterial biofilms, suggesting that TPCP has clinical potential as a novel antibacterial agent for the prevention and treatment of MSSA and MRSA infections.

A genetic regulatory see-saw of biofilm and virulence in MRSA pathogenesis

Staphylococcus aureus is one of the most common opportunistic human pathogens causing several infectious diseases. Ever since the emergence of the first methicillin-resistant Staphylococcus aureus (MRSA) strain decades back, the organism has been a major cause of hospital-acquired infections (HA-MRSA). The spread of this pathogen across the community led to the emergence of a more virulent subtype of the strain, i.e., Community acquired Methicillin resistant Staphylococcus aureus (CA-MRSA). Hence, WHO has declared Staphylococcus aureus as a high-priority pathogen. MRSA pathogenesis is remarkable because of the ability of this "superbug" to form robust biofilm both in vivo and in vitro by the formation of polysaccharide intercellular adhesin (PIA), extracellular DNA (eDNA), wall teichoic acids (WTAs), and capsule (CP), which are major components that impart stability to a biofilm. On the other hand, secretion of a diverse array of virulence factors such as hemolysins, leukotoxins, enterotoxins, and Protein A regulated by agr and sae two-component systems (TCS) aids in combating host immune response. The up- and downregulation of adhesion genes involved in biofilm formation and genes responsible for synthesizing virulence factors during different stages of infection act as a genetic regulatory see-saw in the pathogenesis of MRSA. This review provides insight into the evolution and pathogenesis of MRSA infections with a focus on genetic regulation of biofilm formation and virulence factors secretion.

Impact of cell-free supernatant of lactic acid bacteria on Staphylococcus aureus biofilm and its metabolites

Introduction

A safe bio-preservative agent, lactic acid bacteria (LAB) can inhibit the growth of pathogenic bacteria and spoilage organisms. Its cell-free supernatant (LAB-CFS), which is rich in bioactive compounds, is what makes LAB antibacterial work.

Methods

This study focused on the changes in biofilm activity and related metabolic pathways of S. aureus treated with lactic acid bacteria planktonic CFS (LAB-pk-CFS) and biofilm state (LAB-bf-CFS).

Results

The findings demonstrated that the LAB-CFS treatment considerably slowed Staphylococcus aureus (S. aureus) growth and prevented it from forming biofilms. Additionally, it inhibits the physiological traits of the S. aureus biofilm, including hydrophobicity, motility, eDNA, and PIA associated to the biofilm. The metabolites of S. aureus biofilm treated with LAB-CFS were greater in the LAB-bf-CFS than they were in the LAB-pk-CFS, according to metabolomics studies. Important metabolic pathways such amino acids and carbohydrates metabolism were among the most noticeably altered metabolic pathways.

Discussion

These findings show that LAB-CFS has a strong potential to combat S. aureus infections.

Secreted mammalian DNases protect against systemic bacterial infection by digesting biofilms

Extracellular DNase DNASE1L3 maintains tolerance to self-DNA in humans and mice, whereas the role of its homolog DNASE1 remains controversial, and the overall function of secreted DNases in immunity is unclear. We report that deletion of murine DNASE1 neither caused autoreactivity in isolation nor exacerbated lupus-like disease in DNASE1L3-deficient mice. However, combined deficiency of DNASE1 and DNASE1L3 rendered mice susceptible to bloodstream infection with Staphylococcus aureus. DNASE1/DNASE1L3 double-deficient mice mounted a normal innate response to S. aureus and did not accumulate neutrophil extracellular traps (NETs). However, their kidneys manifested severe pathology, increased bacterial burden, and biofilm-like bacterial lesions that contained bacterial DNA and excluded neutrophils. Furthermore, systemic administration of recombinant DNASE1 protein during S. aureus infection rescued the mortality of DNase-deficient mice and ameliorated the disease in wild-type mice. Thus, DNASE1 and DNASE1L3 jointly facilitate the control of bacterial infection by digesting extracellular microbial DNA in biofilms, suggesting the original evolutionary function of secreted DNases as antimicrobial agents.

1H, 15N, and 13C chemical shift backbone resonance NMR assignment of the accumulation-associated protein (Aap) lectin domain from Staphylococcus epidermidis

Staphylococcus epidermidis is the leading causative agent for hospital-acquired infections, especially device-related infections, due to its ability to form biofilms. The accumulation-associated protein (Aap) of S. epidermidis is primarily responsible for biofilm formation and consists of two domains, A and B. It was found that the A domain is responsible for the attachment to the abiotic/biotic surface, whereas the B domain is responsible for the accumulation of bacteria during biofilm formation. One of the parts of the A domain is the Aap lectin, which is a carbohydrate-binding domain having 222 amino acids in its structure. Here we report the near complete backbone chemical shift assignments for the lectin domain, as well as its predicted secondary structure. This data will provide a platform for future NMR studies to explore the role of lectin in biofilm formation.

Zerumbone Disturbs the Extracellular Matrix of Fluconazole-Resistant Candida albicans Biofilms

This study assessed the effect of zerumbone (ZER) against fluconazole-resistant (CaR) and -susceptible Candida albicans (CaS) biofilms and verified the influence of ZER on extracellular matrix components. Initially, to determine the treatment conditions, the minimum inhibitory concentration (MIC), the minimum fungicidal concentration (MFC) and the survival curve were evaluated. Biofilms were formed for 48 h and exposed to ZER at concentrations of 128 and 256 µg/mL for 5, 10 and 20 min (n = 12). One group of biofilms did not receive the treatment in order to monitor the effects. The biofilms were evaluated to determine the microbial population (CFU/mL), and the extracellular matrix components (water-soluble polysaccharides (WSP), alkali-soluble polysaccharides (ASPs), proteins and extracellular DNA (eDNA), as well as the biomass (total and insoluble) were quantified. The MIC value of ZER for CaS was 256 μg/mL, and for CaR, it was 64 μg/mL. The survival curve and the MFC value coincided for CaS (256 μg/mL) and CaR (128 μg/mL). ZER reduced the cellular viability by 38.51% for CaS and by 36.99% for CaR. ZER at 256 µg/mL also reduced the total biomass (57%), insoluble biomass (45%), WSP (65%), proteins (18%) and eDNA (78%) of CaS biofilms. In addition, a reduction in insoluble biomass (13%), proteins (18%), WSP (65%), ASP (10%) and eDNA (23%) was also observed in the CaR biofilms. ZER was effective against fluconazole-resistant and -susceptible C. albicans biofilms and disturbed the extracellular matrix.

Approaching prosthesis infection environment: Development of an innovative in vitro Staphylococcus aureus biofilm model

The major role and implication of bacterial biofilms in the case of bone and prosthesis infections have been highlighted and often linked to implant colonization. Management strategies of these difficult-to-treat infections consist in surgeries and antibiotic treatment, but the rate of relapse remains high, especially if Staphylococcus aureus, a high-virulent pathogen, is involved. Therapeutic approaches are not adapted to the specific features of biofilm in bone context whereas infectious environment is known to importantly influence biofilm structure. In the present study, we aim to characterize S. aureus SH1000 (methicillin-sensitive strain, MSSA) and USA300 (methicillin-resistant strain, MRSA) biofilm on different surfaces mimicking the periprosthetic environment. As expected, protein adsorption on titanium enhanced the number of adherent bacteria for both strains. On bone explant, USA300 adhered more than SH1000. The simultaneous presence of two different surfaces was also found to change the bacterial behaviour. Thus, proteins adsorption on titanium and bone samples (from bank or directly recovered after an arthroplasty) were found to be key parameters that influence S. aureus biofilm formation: adhesion, matrix production and biofilm-related gene regulation. These results highlighted the need for new biofilm models, more relevant with the infectious environment by using adapted culture medium and presence of surfaces that are representative of in situ conditions to better evaluate therapeutic strategies against biofilm.

Clinical Impact of Staphylococcus aureus Skin and Soft Tissue Infections

The pathogenic bacterium Staphylococcus aureus is the most common pathogen isolated in skin-and-soft-tissue infections (SSTIs) in the United States. Most S. aureus SSTIs are caused by the epidemic clone USA300 in the USA. These infections can be serious; in 2019, SSTIs with S. aureus were associated with an all-cause, age-standardized mortality rate of 0.5 globally. Clinical presentations of S. aureus SSTIs vary from superficial infections with local symptoms to monomicrobial necrotizing fasciitis, which can cause systemic manifestations and may lead to serious complications or death. In order to cause skin infections, S. aureus employs a host of virulence factors including cytolytic proteins, superantigenic factors, cell wall-anchored proteins, and molecules used for immune evasion. The immune response to S. aureus SSTIs involves initial responders such as keratinocytes and neutrophils, which are supported by dendritic cells and T-lymphocytes later during infection. Treatment for S. aureus SSTIs is usually oral therapy, with parenteral therapy reserved for severe presentations; it ranges from cephalosporins and penicillin agents such as oxacillin, which is generally used for methicillin-sensitive S. aureus (MSSA), to vancomycin for methicillin-resistant S. aureus (MRSA). Treatment challenges include adverse effects, risk for Clostridioides difficile infection, and potential for antibiotic resistance.

Staphylococcus aureus Behavior on Artificial Surfaces Mimicking Bone Environment

Infections, which interfere with bone regeneration, may be a critical issue to consider during the development of biomimetic material. Calcium phosphate (CaP) and type I collagen substrates, both suitable for bone-regeneration dedicated scaffolds, may favor bacterial adhesion. Staphylococcus aureus possesses adhesins that allow binding to CaP or collagen. After their adhesion, bacteria may develop structures highly tolerant to immune system attacks or antibiotic treatments: the biofilms. Thus, the choice of material used for scaffolds intended for bone sites is essential to provide devices with the ability to prevent bone and joint infections by limiting bacterial adhesion. In this study, we compared the adhesion of three different S. aureus strains (CIP 53.154, SH1000, and USA300) on collagen- and CaP-coating. Our objective was to evaluate the capacity of bacteria to adhere to these different bone-mimicking coated supports to better control the risk of infection. The three strains were able to adhere to CaP and collagen. The visible matrix components were more important on CaP- than on collagen-coating. However, this difference was not reflected in biofilm gene expression for which no change was observed between the two tested surfaces. Another objective was to evaluate these bone-mimicking coatings for the development of an in vitro model. Thus, CaP, collagen-coatings, and the titanium-mimicking prosthesis were simultaneously tested in the same bacterial culture. No significant differences were found compared to adhesion on surfaces independently tested. In conclusion, these coatings used as bone substitutes can easily be colonized by bacteria, especially CaP-coating, and must be used with an addition of antimicrobial molecules or strategies to avoid bacterial biofilm development.

A Heterocatalytic Metal-Organic Framework to Stimulate Dispersal and Macrophage Combat with Infectious Biofilms

Eradication of infectious biofilms is becoming increasingly difficult due to the growing number of antibiotic-resistant strains. This necessitates development of nonantibiotic-based, antimicrobial approaches. To this end, we designed a heterocatalytic metal-organic framework composed of zirconium 1,4-dicarboxybenzene (UiO-66) with immobilized Pt nanoparticles (Pt-NP/UiO-66). Pt-NP/UiO-66 enhanced singlet-oxygen generation compared with Pt nanoparticles or UiO-66, particularly in an acidic environment. Singlet-oxygen generation degraded phosphodiester bonds present in eDNA gluing biofilms together and therewith dispersed biofilms. Remaining biofilms possessed a more open structure. Concurrently, Pt-NP/UiO-66 stimulated macrophages to adapt a more M1-like, "fighting" phenotype, moving faster toward their target bacteria and showing increased bacterial killing. As a combined effect of biofilm dispersal and macrophage polarization, a subcutaneous Staphylococcus aureus biofilm in mice was more readily eradicated by Pt-NP/UiO-66 than by Pt nanoparticles or UiO-66. Therewith, heterocatalytic Pt-NP/UiO-66 metal-organic frameworks constitute a nonantibiotic-based strategy to weaken protective matrices and disperse infectious biofilms, while strengthening macrophages in bacterial killing.

eDNA Provides a Scaffold for Autoaggregation of B. subtilis in Bacterioplankton Suspension

The self-binding of bacterial cells, or autoaggregation, is, together with surface colonization, one of the first steps in the formation of a mature biofilm. In this work, the autoaggregation of B. subtilis in dilute bacterial suspensions was studied. The dynamics of cell lysis, eDNA release, and bacterial autoaggregate assembly were determined and related to the spatial autocorrelation of bacterial cells in dilute planktonic bacterial suspensions. The non-random distribution of cells was associated with an eDNA network, which stabilized the initial bacterial cell-cell aggregates. Upon the addition of DNase I, the aggregates were dispersed. The release of eDNA during cell lysis allows for the entrapment of bacterial drifters at a radius several times the size of the dying bacteria. The size of bacterial aggregates increased from 2 to about 100 μm in diameter in dilute bacterial suspensions. The results suggest that B. subtilis cells form previously unnoticed continuum of autoaggregate structures during planktonic growth.

The Regulations of Essential WalRK Two-Component System on Enterococcus faecalis

Enterococcus faecalis (E. faecalis) is a Gram-positive, facultative anaerobic bacterium that is highly adaptable to its environment. In humans, it can cause serious infections with biofilm formation. With increasing attention on its health threat, prevention and control of biofilm formation in E. faecalis have been observed. Many factors including polysaccharides as well as autolysis, proteases, and eDNA regulate biofilm formation. Those contributors are regulated by several important regulatory systems involving the two-component signal transduction system (TCS) for its adaptation to the environment. Highly conserved WalRK as one of 17 TCSs is the only essential TCS in E. faecalis. In addition to biofilm formation, various metabolisms, including cell wall construction, drug resistance, as well as interactions among regulatory systems and resistance to the host immune system, can be modulated by the WalRK system. Therefore, WalRK has been identified as a key target for E. faecalis infection control. In the present review, the regulation of WalRK on E. faecalis pathogenesis and associated therapeutic strategies are demonstrated.

The gene regulatory network of Staphylococcus aureus ST239-SCCmecIII strain Bmb9393 and assessment of genes associated with the biofilm in diverse backgrounds

Introduction

Staphylococcus aureus is one of the most prevalent and relevant pathogens responsible for a wide spectrum of hospital-associated or community-acquired infections. In addition, methicillin-resistant Staphylococcus aureus may display multidrug resistance profiles that complicate treatment and increase the mortality rate. The ability to produce biofilm, particularly in device-associated infections, promotes chronic and potentially more severe infections originating from the primary site. Understanding the complex mechanisms involved in planktonic and biofilm growth is critical to identifying regulatory connections and ways to overcome the global health problem of multidrug-resistant bacteria.

Methods

In this work, we apply literature-based and comparative genomics approaches to reconstruct the gene regulatory network of the high biofilm-producing strain Bmb9393, belonging to one of the highly disseminating successful clones, the Brazilian epidemic clone. To the best of our knowledge, we describe for the first time the topological properties and network motifs for the Staphylococcus aureus pathogen. We performed this analysis using the ST239-SCCmecIII Bmb9393 strain. In addition, we analyzed transcriptomes available in the literature to construct a set of genes differentially expressed in the biofilm, covering different stages of the biofilms and genetic backgrounds of the strains.

Results and discussion

The Bmb9393 gene regulatory network comprises 1,803 regulatory interactions between 64 transcription factors and the non-redundant set of 1,151 target genes with the inclusion of 19 new regulons compared to the N315 transcriptional regulatory network published in 2011. In the Bmb9393 network, we found 54 feed-forward loop motifs, where the most prevalent were coherent type 2 and incoherent type 2. The non-redundant set of differentially expressed genes in the biofilm consisted of 1,794 genes with functional categories relevant for adaptation to the variable microenvironments established throughout the biofilm formation process. Finally, we mapped the set of genes with altered expression in the biofilm in the Bmb9393 gene regulatory network to depict how different growth modes can alter the regulatory systems. The data revealed 45 transcription factors and 876 shared target genes. Thus, the gene regulatory network model provided represents the most up-to-date model for Staphylococcus aureus, and the set of genes altered in the biofilm provides a global view of their influence on biofilm formation from distinct experimental perspectives and different strain backgrounds.

Therapeutic Strategies against Biofilm Infections

A biofilm is an aggregation of surface-associated microbial cells that is confined in an extracellular polymeric substance (EPS) matrix. Infections caused by microbes that form biofilms are linked to a variety of animals, including insects and humans. Antibiotics and other antimicrobials can be used to remove or eradicate biofilms in order to treat infections. However, due to biofilm resistance to antibiotics and antimicrobials, clinical observations and experimental research clearly demonstrates that antibiotic and antimicrobial therapies alone are frequently insufficient to completely eradicate biofilm infections. Therefore, it becomes crucial and urgent for clinicians to properly treat biofilm infections with currently available antimicrobials and analyze the results. Numerous biofilm-fighting strategies have been developed as a result of advancements in nanoparticle synthesis with an emphasis on metal oxide np. This review focuses on several therapeutic strategies that are currently being used and also those that could be developed in the future. These strategies aim to address important structural and functional aspects of microbial biofilms as well as biofilms' mechanisms for drug resistance, including the EPS matrix, quorum sensing (QS), and dormant cell targeting. The NPs have demonstrated significant efficacy against bacterial biofilms in a variety of bacterial species. To overcome resistance, treatments such as nanotechnology, quorum sensing, and photodynamic therapy could be used.

Baicalein Inhibits the Staphylococcus aureus Biofilm and the LuxS/AI-2 System in vitro

Introduction

Staphylococcus aureus (S. aureus) is a common cause of mastitis in dairy cows, a condition that has a significant economic impact. S. aureus displays quorum sensing (QS) system-controlled virulence characteristics, like biofilm formation, that make therapy challenging. In order to effectively combat S. aureus, one potential technique is to interfere with quorum sensing.

Methods

This study evaluated the effects of different Baicalin (BAI) concentrations on the growth and the biofilm of S. aureus isolates, including the biofilm formation and mature biofilm clearance. The binding activity of BAI to LuxS was verified by molecular docking and kinetic simulations. The secondary structure of LuxS in the formulations was characterized using fluorescence quenching and Fourier transform infrared (FTIR) spectroscopy. Additionally, using fluorescence quantitative PCR, the impact of BAI on the transcript levels of the luxS and biofilm-related genes was investigated. The impact of BAI on LuxS at the level of protein expression was also confirmed by a Western blotting investigation.

Results

According to the docking experiments, they were able to engage with the amino acid residues in LuxS and BAI through hydrogen bonding. The results of molecular dynamics simulations and the binding free energy also confirmed the stability of the complex and supported the experimental results. BAI showed weak inhibitory activity against S. aureus but significantly reduced biofilm formation and disrupted mature biofilms. BAI also downregulated luxS and biofilm-associated genes' mRNA expression. Successful binding was confirmed using fluorescence quenching and FTIR.

Discussion

We thus report that BAI inhibits the S. aureus LuxS/AI-2 system for the first time, which raises the possibility that BAI could be employed as a possible antimicrobial drug to treat S. aureus strain-caused biofilms.

Hydrogen peroxide enhances the efficacy of photodynamic therapy against Candida albicans biofilms

The present study aimed to evaluate the effectiveness of hydrogen peroxide (H₂O₂) combined with antimicrobial photodynamic therapy (aPDT) on biofilms formed by Candida albicans strains which are either susceptible to or resistant to fluconazole. Biofilms were grown and treated with H₂O₂, followed by the application of Photodithazine® (P) and red light-emitting diode (LED) (L) either separately or combined (n = 12). After the treatment, biofilms were evaluated by estimating colony-forming unit ml^-1, extracellular matrix components [water -soluble and -insoluble polysaccharides, proteins, extracellular DNA (eDNA)], biomass (total and insoluble dry-weight), and protein concentration. Biofilms formed by both strains presented a significant reduction in cell viability, biomass, extracellular matrix components (both types of polysaccharides, eDNA), and proteins (in the soluble and insoluble portion of biofilms) compared to the control. Microscopy images of the biofilms after treatments showed disarticulation of the matrix and scattered fungal cells. The application of H₂O₂ can disturb the organization of the extracellular matrix, and its association with aPDT potentiated the effect of the treatment.

A Review of Biofilm Formation of Staphylococcus aureus and Its Regulation Mechanism

Bacteria can form biofilms in natural and clinical environments on both biotic and abiotic surfaces. The bacterial aggregates embedded in biofilms are formed by their own produced extracellular matrix. Staphylococcus aureus (S. aureus) is one of the most common pathogens of biofilm infections. The formation of biofilm can protect bacteria from being attacked by the host immune system and antibiotics and thus bacteria can be persistent against external challenges. Therefore, clinical treatments for biofilm infections are currently encountering difficulty. To address this critical challenge, a new and effective treatment method needs to be developed. A comprehensive understanding of bacterial biofilm formation and regulation mechanisms may provide meaningful insights against antibiotic resistance due to bacterial biofilms. In this review, we discuss an overview of S. aureus biofilms including the formation process, structural and functional properties of biofilm matrix, and the mechanism regulating biofilm formation.

eDNA, Amyloid Fibers and Membrane Vesicles Identified in Pseudomonas fluorescens SBW25 Biofilms

Pseudomonas fluorescens SBW25 is a model soil- and plant-associated bacterium capable of forming a variety of air-liquid interface biofilms in experimental microcosms and on plant surfaces. Previous investigations have shown that cellulose is the primary structural matrix component in the robust and well-attached Wrinkly Spreader biofilm, as well as in the fragile Viscous Mass biofilm. Here, we demonstrate that both biofilms include extracellular DNA (eDNA) which can be visualized using confocal laser scanning microscopy (CLSM), quantified by absorbance measurements, and degraded by DNase I treatment. This eDNA plays an important role in cell attachment and biofilm development. However, exogenous high-molecular-weight DNA appears to decrease the strength and attachment levels of mature Wrinkly Spreader biofilms, whereas low-molecular-weight DNA appears to have little effect. Further investigation with CLSM using an amyloid-specific fluorophore suggests that the Wrinkly Spreader biofilm might also include Fap fibers, which might be involved in attachment and contribute to biofilm strength. The robust nature of the Wrinkly Spreader biofilm also allowed us, using MALDI-TOF mass spectrometry, to identify matrix-associated proteins unable to diffuse out of the structure, as well as membrane vesicles which had a different protein profile compared to the matrix-associated proteins. CLSM and DNase I treatment suggest that some vesicles were also associated with eDNA. These findings add to our understanding of the matrix components in this model pseudomonad, and, as found in other biofilms, biofilm-specific products and material from lysed cells contribute to these structures through a range of complex interactions.

Human Osteoblast-Conditioned Media Can Influence Staphylococcus aureus Biofilm Formation

Osteoblasts are bone-forming and highly active cells participating in bone homeostasis. In the case of osteomyelitis and more specifically prosthetic joint infections (PJI) for which Staphylococcus aureus (S. aureus) is mainly involved, the interaction between osteoblasts and S. aureus results in impaired bone homeostasis. If, so far, most of the studies of osteoblasts and S. aureus interactions were focused on osteoblast response following direct interactions with co-culture and/or internalization models, less is known about the effect of osteoblast factors on S. aureus biofilm formation. In the present study, we investigated the effect of human osteoblast culture supernatant on methicillin sensitive S. aureus (MSSA) SH1000 and methicillin resistant S. aureus (MRSA) USA300. Firstly, Saos-2 cell line was incubated with either medium containing TNF-α to mimic the inflammatory periprosthetic environment or with regular medium. Biofilm biomass was slightly increased for both strains in the presence of culture supernatant collected from Saos-2 cells, stimulated or not with TNF-α. In such conditions, SH1000 was able to develop microcolonies, suggesting a rearrangement in biofilm organization. However, the biofilm matrix and regulation of genes dedicated to biofilm formation were not substantially changed. Secondly, culture supernatant obtained from primary osteoblast culture induced varied response from SH1000 strain depending on the different donors tested, whereas USA300 was only slightly affected. This suggested that the sensitivity to bone cell secretions is strain dependent. Our results have shown the impact of osteoblast secretions on bacteria and further identification of involved factors will help to manage PJI.

Evaluation of the antimicrobial function of Ginkgo biloba exocarp extract against clinical bacteria and its effect on Staphylococcus haemolyticus by disrupting biofilms

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Ginkgo biloba L. (Ginkgo nuts) has been used for a long time as a critical Chinese medicine material to treat cough and asthma, as well as a disinfectant. Similar records were written in the Compendium of Materia Medica (Ben Cao Gang Mu, pinyin in Chinese) and Sheng Nong's herbal classic (Shen Nong Ben Cao Jing, pinyin in Chinese). Recent research has shown that Ginkgo biloba exocarp extract (GBEE) has the functions of unblocking blood vessels and improving brain function, as well as antitumour activity and antibacterial activity. GBEE was shown to inhibit methicillin-resistant Staphylococcus aureus (MRSA) biofilm formation as a traditional Chinese herb in our previous report in this journal. AIM OF THE STUD: yThe antibiotic resistance of clinical bacteria has recently become increasingly serious. Thus, this study aimed to investigate the Ginkgo biloba exocarp extract (GBEE) antibacterial lineage, as well as its effect and mechanism on S. haemolyticus biofilms. This study will provide a new perspective on clinical multidrug resistant (MDR) treatment with ethnopharmacology herbs.

METHODS

The microbroth dilution assay was carried out to measure the antibacterial effect of GBEE on 13 types of clinical bacteria. Bacterial growth curves with or without GBEE treatment were drawn at different time points. The potential targets of GBEE against S. haemolyticus were screened by transcriptome sequencing. The effects of GBEE on bacterial biofilm formation and mature biofilm disruption were determined by crystal violet staining and scanning electron microscopy. The metabolic activity of bacteria inside the biofilm was assessed by colony-forming unit (CFU) counting and (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2HY-tetrazolium bromide (MTT) assay. Quantitative polymerase chain reaction (qPCR) was used to measure the gene expression profile of GBEE on S. haemolyticus biofilm-related factors.

RESULTS

The results showed that GBEE has bacteriostatic effects on 3 g-positive (G⁺) and 2 g-negative (G^-) bacteria among 13 species of clinical bacteria. The antibacterial effect of GBEE supernatant liquid was stronger than the antibacterial effect of GBEE supernviaould-like liquid. GBEE supernatant liquid inhibited the growth of S. epidermidis, S. haemolyticus, and E. faecium at shallow concentrations with minimum inhibitory concentrations (MICs) of 2 μg/ml, 4 μg/ml and 8 μg/ml, respectively. Genes involved in quorum sensing, two-component systems, folate biosynthesis, and ATP-binding cassette (ABC) transporters were differentially expressed in GBEE-treated groups compared with controls. Crystal violet, scanning electron microscopy (SEM) and MTT assays showed that GBEE suppressed S. haemolyticus biofilm formation in a dose-dependent manner. Moreover, GBEE supernatant liquid downregulated cidA, cidB and atl, which are involved in cell lysis and extracellular DNA (eDNA) release, as well as downregulated the cbp, ebp and fbp participation in encoding cell-surface binding proteins.

CONCLUSIONS

GBEE has an excellent antibacterial effect on gram-positive bacteria and also inhibits the growth of gram-negative bacteria, such as A. baumannii (carbapenem-resistant Acinetobacter baumannii) CRABA and S. maltophilia. GBEE inhibits the biofilm formation of S. haemolyticus by altering the regulation and biofilm material-related genes, including the release of eDNA and cell-surface binding proteins.

Correlation Analysis between Chronic Osteomyelitis and Bacterial Biofilm

Objective

To study the role of bacterial biofilm (BBF) in the formation of chronic osteomyelitis and its prevention and treatment.

Methods

In this paper, a large amount of relevant literature was searched for analysis and summary, and the key words "chronic osteomyelitis," "bacterial biofilm," "infection," and "debridement" were searched in databases, mainly CNKI, Wanfang, and Wipu. The search was conducted until December 2020. The role of bacterial biofilm formation in chronic osteomyelitis and its prevention were analyzed.

Results

Chronic osteomyelitis is formed mainly due to poor blood supply and drug-resistant bacteria, of which cellular biofilm is the most important cause. BBF forms on the surface of necrotic soft tissue and bone tissue, which has a protective effect on bacteria and greatly enhances their resistance to antibiotics, leading to difficulties in complete bacterial clearance and recurrent infections in osteomyelitis.

Conclusion

Through an in-depth study of the molecular biology and signal transduction of osteomyelitis biofilm, antibiotic biofilm treatment strategies and surgical debridement remain the focus of clinical translation of chronic osteomyelitis.

Pyrancoumarin derivative LP4C targeting of pyrimidine de novo synthesis pathway inhibits MRSA biofilm and virulence

Staphylococcus aureus poses a serious public health threat because of its multidrug resistance and biofilm formation ability. Hence, developing novel anti-biofilm agents and finding targets are needed to mitigate the proliferation of drug-resistant pathogens. In our previous study, we showed that the pyrancoumarin derivative 2-amino-4-(2,6-dichlorophenyl)-3-cyano-5-oxo-4H, 5H- pyrano [3,2c] chromene (LP4C) can destroy the biofilm of methicillin-resistant S. aureus (MRSA) in vitro and in vivo. Here, we further explored the possible mechanism of LP4C as a potential anti-biofilm drug. We found that LP4C inhibits the expression of enzymes involved in the de novo pyrimidine pathway and attenuates the virulence of MRSA USA300 strain without affecting the agr or luxS quorum sensing system. The molecular docking results indicated that LP4C forms interactions with the key amino acid residues of pyrR protein, which functions as the important regulator of bacterial pyrimidine synthesis. These findings reveal that pyrancoumarin derivative LP4C inhibits MRSA biofilm formation and targeting pyrimidine de novo synthesis pathway.

Geraniol inhibits biofilm formation of methicillin-resistant Staphylococcus aureus and increase the therapeutic effect of vancomycin in vivo

Methicillin-resistant Staphylococcus aureus (MRSA) is among the common drug resistant bacteria, which has gained worldwide attention due to its high drug resistance and infection rates. Biofilms produced by S. aureus are known to increase antibiotic resistance, making the treatment of S. aureus infections even more challenging. Hence, inhibition of biofilm formation has become an alternative strategy for controlling persistent infections. In this study, we evaluated the efficacy of geraniol as a treatment for MRSA biofilm infection. The results of crystal violet staining indicated that 256 μg/mL concentration of geraniol inhibited USA300 biofilm formation by 86.13% and removed mature biofilms by 49.87%. Geraniol exerted its anti-biofilm effect by influencing the major components of the MRSA biofilm structure. We found that geraniol inhibited the synthesis of major virulence factors, including staphyloxanthin and autolysins. The colony count revealed that geraniol inhibited staphyloxanthin and sensitized USA300 cells to hydrogen peroxide. Interestingly, geraniol not only reduced the release of extracellular nucleic acids (eDNA) but also inhibited cell autolysis. Real-time polymerase chain reaction data revealed the downregulation of genes involved in biofilm formation, which verified the results of the phenotypic analysis. Geraniol increased the effect of vancomycin in eliminating USA300 biofilms in a mouse infection model. Our findings revealed that geraniol effectively inhibits biofilm formation in vitro. Furthermore, in combination with vancomycin, geraniol can reduce the biofilm adhesion to the implant in mice. This suggests the potential of geraniol as an anti-MRSA biofilm drug and can provide a solution for the clinical treatment of biofilm infection.

Streptococcus mutans PrsA mediates AtlA secretion contributing to extracellular DNA release and biofilm formation in the pathogenesis of infective endocarditis

The role of secretion chaperone-regulated virulence proteins in the pathogenesis of infective endocarditis (IE) induced by viridans streptococci such as Streptococcus mutans is unclear. In this study, we investigated the contribution of the foldase protein PrsA, a putative parvulin-type peptidyl-prolyl isomerase, to the pathogenesis of S. mutans-induced IE. We found that a prsA-deficient strain had reduced virulence in terms of formation of vegetation on damaged heart valves, as well as reduced autolysis activity, eDNA release and biofilm formation capacity. The secretion and surface exposure of AtlA in vitro was reduced in the prsA-deficient mutant strain, and complementation of recombinant AtlA in the culture medium restored a wild type biofilm phenotype of the prsA-deficient mutant strain. This result suggests that secretion and surface localization of AtlA is regulated by PrsA during biofilm formation. Together, these results demonstrate that S. mutans PrsA could regulate AtlA-mediated eDNA release to contribute to biofilm formation in the pathogenesis of IE.

Small-Molecule-Induced Activation of Cellular Respiration Inhibits Biofilm Formation and Triggers Metabolic Remodeling in Staphylococcus aureus

Staphylococcus aureus, a major pathogen of community-acquired and nosocomial-associated infections, forms biofilms consisting of extracellular matrix-embedded cell aggregates. S. aureus biofilm formation on implanted medical devices can cause local and systemic infections due to the dispersion of cells from the biofilms. Usually, conventional antibiotic treatments are not effective against biofilm-related infections, and there is no effective treatment other than removing the contaminated devices. Therefore, the development of new therapeutic agents to combat biofilm-related infections is urgently needed. We conducted high-throughput screening of S. aureus biofilm inhibitors and obtained a small compound, JBD1. JBD1 strongly inhibits biofilm formation of S. aureus, including methicillin-resistant strains. In addition, JBD1 activated the respiratory activity of S. aureus cells and increased the sensitivity to aminoglycosides. Furthermore, it was shown that the metabolic profile of S. aureus was significantly altered in the presence of JBD1 and that metabolic remodeling was induced. Surprisingly, these JBD1-induced phenotypes were blocked by adding an excess amount of the electron carrier menaquinone to suppress respiratory activation. These results indicate that JBD1 induces biofilm inhibition and metabolic remodeling through respiratory activation. This study demonstrates that compounds that enhance the respiratory activity of S. aureus may be potential leads in the development of therapeutic agents for chronic S. aureus-biofilm-related infections.

Targeting the Achilles' Heel of Multidrug-Resistant Staphylococcus aureus by the Endocannabinoid Anandamide

Antibiotic-resistant Staphylococcus aureus is a major health issue that requires new therapeutic approaches. Accumulating data suggest that it is possible to sensitize these bacteria to antibiotics by combining them with inhibitors targeting efflux pumps, the low-affinity penicillin-binding protein PBP2a, cell wall teichoic acid, or the cell division protein FtsZ. We have previously shown that the endocannabinoid Anandamide (N-arachidonoylethanolamine; AEA) could sensitize drug-resistant S. aureus to a variety of antibiotics, among others, through growth arrest and inhibition of drug efflux. Here, we looked at biochemical alterations caused by AEA. We observed that AEA increased the intracellular drug concentration of a fluorescent penicillin and augmented its binding to membrane proteins with concomitant altered membrane distribution of these proteins. AEA also prevented the secretion of exopolysaccharides (EPS) and reduced the cell wall teichoic acid content, both processes known to require transporter proteins. Notably, AEA was found to inhibit membrane ATPase activity that is necessary for transmembrane transport. AEA did not affect the membrane GTPase activity, and the GTPase cell division protein FtsZ formed the Z-ring of the divisome normally in the presence of AEA. Rather, AEA caused a reduction in murein hydrolase activities involved in daughter cell separation. Altogether, this study shows that AEA affects several biochemical processes that culminate in the sensitization of the drug-resistant bacteria to antibiotics.

Mechanical and microbiological testing concept for activatable anti-infective biopolymer implant coatings

An anti-infective bilayer implant coating with selectively activatable properties was developed to prevent biofilm formation and to support the treatment of periprosthetic infection as a local adjunct to current treatment concepts. In a first step, Ti6Al4V discs were coated with a permanent layer of Poly(l-lactide) (PLLA) including silver ions. The PLLA could be optionally released by the application of extracorporeal shock waves. In a second step, a resorbable layer of triglyceride (TAG) with incorporated antibiotics was applied. The second layer is designed for resorption within weeks. Prior to approval and clinical application, a comprehensive evaluation process to determine mechanical/physical and microbiological properties is obligate. To date, none of the existing test standards covers both drug-releasing and activatable coatings for orthopedic implants. Therefore, a comprehensive test concept was developed to characterize the new coating in a pilot series. The coatings were homogeneously applied on the Ti6Al4V substrate, resulting in an adhesion strength sufficient for non-articulating surfaces for PLLA. Proof of the extracorporeal shockwave activation of PLLA was demonstrated both mechanically and microbiologically, with a simultaneous increase of biocompatibility compared to standard electroplated silver coating. Wettability was significantly reduced for both layers in comparison to the Ti6Al4V substrate. Thus, potentially inhibiting biofilm formation. Furthermore, the TAG coating promoted cell proliferation and bacterial eradication. In conclusion, the testing concept is applicable for similar biopolymer coating systems. Furthermore, the extracorporeal activation could represent a completely new supportive approach for the treatment of periprosthetic joint infections.

Targeting the Holy Triangle of Quorum Sensing, Biofilm Formation, and Antibiotic Resistance in Pathogenic Bacteria

Chronic and recurrent bacterial infections are frequently associated with the formation of biofilms on biotic or abiotic materials that are composed of mono- or multi-species cultures of bacteria/fungi embedded in an extracellular matrix produced by the microorganisms. Biofilm formation is, among others, regulated by quorum sensing (QS) which is an interbacterial communication system usually composed of two-component systems (TCSs) of secreted autoinducer compounds that activate signal transduction pathways through interaction with their respective receptors. Embedded in the biofilms, the bacteria are protected from environmental stress stimuli, and they often show reduced responses to antibiotics, making it difficult to eradicate the bacterial infection. Besides reduced penetration of antibiotics through the intricate structure of the biofilms, the sessile biofilm-embedded bacteria show reduced metabolic activity making them intrinsically less sensitive to antibiotics. Moreover, they frequently express elevated levels of efflux pumps that extrude antibiotics, thereby reducing their intracellular levels. Some efflux pumps are involved in the secretion of QS compounds and biofilm-related materials, besides being important for removing toxic substances from the bacteria. Some efflux pump inhibitors (EPIs) have been shown to both prevent biofilm formation and sensitize the bacteria to antibiotics, suggesting a relationship between these processes. Additionally, QS inhibitors or quenchers may affect antibiotic susceptibility. Thus, targeting elements that regulate QS and biofilm formation might be a promising approach to combat antibiotic-resistant biofilm-related bacterial infections.

Polyethylene terephthalate microplastic fibers increase the release of extracellular antibiotic resistance genes during sewage sludge anaerobic digestion

Microplastic fibers (MFs), as the most frequently detected microplastic shape in sewage sludge, have posed emerging concern for sludge treatment and disposal. However, the effect of MFs on antibiotic resistance genes (ARGs), especially extracellular ARGs (eARGs) during sludge treatment remains far from explicit. Therefore, this study investigated the potential impact of MFs on eARGs during sludge anaerobic digestion (AD), a commonly used sludge treatment method, through long-term operation. The qPCR results showed that both absolute and relative abundances of eARGs increased with the MFs exposure during sludge AD. The average absolute and relative abundances of eight tested eARGs in the AD reactor with the highest MFs dosage (170 items/gTS) were 1.70 and 2.15 times higher than those in the control AD reactor. The metagenomics results further comfirmed the increase of eARGs abundance during sludge anaerobic digestion after MFs exposure and the enhancement did not show significant selectivity. The identification of the potential hosts of eARGs suggested the host numbers of eARGs also increased with MFs exposure, which may suggest enhanced horizonal transformation as a result of increased eARGs. Further exploring the mechansims showed that the genes involved in type IV secretion system was upregulated after MFs exposure, suggesting the active release of eARGs was enhanced with MFs exposure. In contrast, the MFs may not affect the passive release of eARGs as its impact on cell membrance damage was insignificant. The enhanced eARGs in sludge AD process may further accelerate the transport of ARGs in environment, which should be considered during sludge treatment and disposal.

Unravelling the physiological roles of mazEF toxin-antitoxin system on clinical MRSA strain by CRISPR RNA-guided cytidine deaminase

BACKGROUND

Curiosity on toxin-antitoxin modules has increased intensely over recent years as it is ubiquitously present in many bacterial genomes, including pathogens like Methicillin-resistant Staphylococcus aureus (MRSA). Several cellular functions of TA systems have been proposed however, their exact role in cellular physiology remains unresolved.

METHODS

This study aims to find out the impact of the mazEF toxin-antitoxin module on biofilm formation, pathogenesis, and antibiotic resistance in an isolated clinical ST239 MRSA strain, by constructing mazE and mazF mutants using CRISPR-cas9 base-editing plasmid (pnCasSA-BEC). Transcriptome analysis (RNA-seq) was performed for the mazE antitoxin mutant in order to identify the differentially regulated genes. The biofilm formation was also assessed for the mutant strains. Antibiogram profiling was carried out for both the generated mutants followed by murine experiment to determine the pathogenicity of the constructed strains.

RESULTS

For the first time our work showed, that MazF promotes cidA mediated cell death and lysis for biofilm formation without playing any significant role in host virulence as suggested by the murine experiment. Interestingly, the susceptibility to oxacillin, daptomycin and vancomycin was reduced significantly by the activated MazF toxin in the mazE mutant strain.

CONCLUSIONS

Our study reveals that activated MazF toxin leads to resistance to antibiotics like oxacillin, daptomycin and vancomycin. Therefore, in the future, any potential antibacterial drug can be designed to target MazF toxin against the problematic multi-drug resistant bug.

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.

Role of Extracellular DNA in Dalbavancin Activity against Methicillin-Resistant Staphylococcus aureus (MRSA) Biofilms in Patients with Skin and Soft Tissue Infections

Methicillin-resistant Staphylococcus aureus (MRSA) has become the leading cause of skin and soft tissue infections (SSTIs). Biofilm production further complicates patient treatment, contributing to increased bacterial persistence and antibiotic tolerance. The study aimed to explore the efficacy of different antibiotics on biofilm-producing MRSA isolated from patients with SSTI. A total of 32 MRSA strains were collected from patients with SSTI. The MIC and minimal biofilm eradication concentration (MBEC) were measured in planktonic and biofilm growth. The study showed that dalbavancin, linezolid, and vancomycin all inhibited MRSA growth at their EUCAST susceptible breakpoint. Of the MRSA strains, 87.5% (n = 28) were strong biofilm producers (SBPs), while only 12.5% (n = 4) were weak biofilm producers (WBPs). The MBEC90 values for dalbavancin were significantly lower than those of linezolid and vancomycin in all tested strains. We also found that extracellular DNA (eDNA) contributes to the initial microbial attachment and biofilm formation. The amount of eDNA differed among MRSA strains and was significantly higher in those isolates with high dalbavancin and vancomycin tolerance. Exogenously added DNA increased the MBEC90 and protection of biofilm cells from dalbavancin activity. Of note, the relative abundance of eDNA was higher in MRSA biofilms exposed to MBEC90 dalbavancin than in untreated MRSA biofilms and those exposed to sub-MIC90. Overall, dalbavancin was the most active antibiotic against MRSA biofilms at concentrations achievable in the human serum. Moreover, the evidence of a drug-related increase of eDNA and its contribution to antimicrobial drug tolerance reveals novel potential targets for antibiofilm strategies against MRSA. IMPORTANCE Staphylococcus aureus is the most common cause of skin and soft tissue infections (SSTIs) worldwide. In addition, methicillin-resistant S. aureus (MRSA) is increasingly frequent in postoperative infections and responsible for a large number of hospital readmissions and deaths. Biofilm formation by S. aureus is a primary risk factor in SSTIs, due to a higher antibiotic tolerance. Our study showed that the biofilm-forming capacity varied among MRSA strains, although strong biofilm producers were significantly more abundant than weak biofilm producer strains. Notably, dalbavancin demonstrated a potent antibiofilm activity at concentrations achievable in human serum. Nevertheless, dalbavancin activity was affected by an increased concentration of extracellular DNA in the biofilm matrix. This study provides novel insight for designing more targeted therapeutic strategies against MRSA and to prevent or eradicate harmful biofilms.

Identification and profiling of microbial community from industrial sludge

The purpose of this study is to identify microbial communities in pulp and paper industry sludge and their metagenomic profiling on the basis of; phylum, class, order, family, genus and species level. Results revealed that the dominant phyla in 16S rRNA Illumina Miseq analysis inside sludge were Anaerolinea, Pseudomonas, Clostridia, Bacteriodia, Gammaproteobacteria, Spirochetia, Deltaproteobacteria, Spirochaetaceae, Prolixibacteraceae and some unknown microbial strains are also dominant. Metagenomics is a molecular biology-based technology that uses bioinformatics to evaluate huge gene sequences extracted from environmental samples to assess the composition and function of microbiota. The results of metabarcoding of the V3-V4 16S rRNA regions acquired from paired-end Illumina MiSeq sequencing were used to analyze bacterial communities and structure. The present work demonstrates the potential approach to sludge treatment in the open environment via the naturally adapted microorganism, which could be an essential addition to the disposal site. In summary, these investigations indicate that the indigenous microbial community is an acceptable bioresource for remediation or detoxification following secondary treatment. This research aims at understanding the structure of microbial communities and their diversity (%) in highly contaminated sludge to perform in situ bioremediation.

The structural role of bacterial eDNA in the formation of biofilm streamers

Across diverse habitats, bacteria are mainly found as biofilms, surface-attached communities embedded in a self-secreted matrix of extracellular polymeric substances (EPS), which enhance bacterial recalcitrance to antimicrobial treatment and mechanical stresses. In the presence of flow and geometric constraints such as corners or constrictions, biofilms can take the form of long, suspended filaments (streamers), which bear important consequences in industrial and clinical settings by causing clogging and fouling. The formation of streamers is thought to be driven by the viscoelastic nature of the biofilm matrix. Yet, little is known about the structural composition of streamers and how it affects their mechanical properties. Here, using a microfluidic platform that allows growing and precisely examining biofilm streamers, we show that extracellular DNA (eDNA) constitutes the backbone and is essential for the mechanical stability of Pseudomonas aeruginosa streamers. This finding is supported by the observations that DNA-degrading enzymes prevent the formation of streamers and clear already formed ones and that the antibiotic ciprofloxacin promotes their formation by increasing the release of eDNA. Furthermore, using mutants for the production of the exopolysaccharide Pel, an important component of P. aeruginosa EPS, we reveal an concurring role of Pel in tuning the mechanical properties of the streamers. Taken together, these results highlight the importance of eDNA and of its interplay with Pel in determining the mechanical properties of P. aeruginosa streamers and suggest that targeting the composition of streamers can be an effective approach to control the formation of these biofilm structures.

Experimental Polymorphism Survey in Intergenic Regions of the icaADBCR Locus in Staphylococcus aureus Isolates from Periprosthetic Joint Infections

Staphylococcus aureus is a leading cause of prosthetic joint infections (PJI) characterized by bacterial biofilm formation and recalcitrance to immune-mediated clearance and antibiotics. The molecular events behind PJI infection are yet to be unraveled. In this sense, identification of polymorphisms in bacterial genomes may help to establish associations between sequence variants and the ability of S. aureus to cause PJI. Here, we report an experimental nucleotide-level survey specifically aimed at the intergenic regions (IGRs) of the icaADBCR locus, which is responsible for the synthesis of the biofilm exopolysaccharide PIA/PNAG, in a collection of strains sampled from PJI and wounds. IGRs of the icaADBCR locus were highly conserved and no PJI-specific SNPs were found. Moreover, polymorphisms in these IGRs did not significantly affect transcription of the icaADBC operon under in vitro laboratory conditions. In contrast, an SNP within the icaR coding region, resulting in a V176E change in the transcriptional repressor IcaR, led to a significant increase in icaADBC operon transcription and PIA/PNAG production and a reduction in S. aureus virulence in a Galleria mellonella infection model. In conclusion, SNPs in icaADBCR IGRs of S. aureus isolates from PJI are not associated with icaADBC expression, PIA/PNAG production and adaptation to PJI.

Real time monitoring of Staphylococcus aureus biofilm sensitivity towards antibiotics with isothermal microcalorimetry

Biofilm-associated infections with Staphylococcus aureus are difficult to treat even after administration of antibiotics that according to the standard susceptibility assays are effective. Currently, the assays used in the clinical laboratories to determine the sensitivity of S. aureus towards antibiotics are not representing the behaviour of biofilm-associated S. aureus, since these assays are performed on planktonic bacteria. In research settings, microcalorimetry has been used for antibiotic susceptibility studies. Therefore, in this study we investigated if we can use isothermal microcalorimetry to monitor the response of biofilm towards antibiotic treatment in real-time. We developed a reproducible method to generate biofilm in an isothermal microcalorimeter setup. Using this system, the sensitivity of 5 methicillin-sensitive S. aureus (MSSA) and 5 methicillin-resistant S. aureus (MRSA) strains from different genetic lineages were determined towards: flucloxacillin, cefuroxime, cefotaxime, gentamicin, rifampicin, vancomycin, levofloxacin, clindamycin, erythromycin, linezolid, fusidic acid, co-trimoxazole, and doxycycline. In contrast to conventional assays, our calorimetry-based biofilm susceptibility assay showed that S. aureus biofilms, regardless MSSA or MRSA, can survive the exposure to the maximum serum concentration of all tested antibiotics. The only treatment with a single antibiotic showing a significant reduction in biofilm survival was rifampicin, yet in 20% of the strains, emerging antibiotic resistance was observed. Furthermore, the combination of rifampicin with flucloxacillin, vancomycin or levofloxacin was able to prevent S. aureus biofilm from becoming resistant to rifampicin. Isothermal microcalorimetry allows real-time monitoring of the sensitivity of S. aureus biofilms towards antibiotics in a fast and reliable way.

A DNase-mimetic artificial enzyme for the eradication of drug-resistant bacterial biofilm infections

The construction of multifunctional nano-enzymes is a feasible strategy for fighting multi-drug resistant (MDR) bacterial biofilm-associated infections. Extracellular DNA (eDNA) is an important functional part of biofilm formation, including the initial adherence of bacteria to subsequent development and eventual maturation. A nano-enzyme platform of graphene oxide-based nitrilotriacetic acid-cerium(IV) composite (GO-NTA-Ce) against bacterial biofilm infection has been developed. When located at the site of bacteria-associated infection, GO-NTA-Ce could inhibit the biofilm formation and effectively disperse the formed biofilm by degrading the eDNA. In addition to Ce-mediated deoxyribonuclease (DNase)-like activity, near-infrared laser irradiation of GO-NTA-Ce could produce local hyperthermia to kill the bacteria that lost the protection by the biofilm matrix. In addition, graphene is also a new green broad-spectrum antimicrobial material that can exert its antimicrobial effects through physical damage and chemical damage. In short, our GO-NTA-Ce nano-enzyme platform is capable of effectively eradicating drug-resistant bacterial biofilm infections through the triple action of DNase-like enzyme properties, photothermal therapy, and graphene-based antimicrobial activity, and the nano-composite has excellent potential for the treatment of MDR bacterial biofilm infections.

DNase enhances photodynamic therapy against fluconazole-resistant Candida albicans biofilms

OBJECTIVE

This study evaluated the effectiveness of DNase I combined with antimicrobial photodynamic therapy, mediated by Photodithazine^® and light-emitting diode light, against biofilms formed by a fluconazole-resistant Candida albicans strain (ATCC 96901) and two clinical isolates (R14 and R70).

MATERIALS AND METHODS

Biofilms were grown for 48 h and exposed to DNase for 5 min, followed by application of a photosensitizer (P) and light (L), either singly or combined (P+L+, P-L+, P+L-, P-L-, P-L-DNase, P+L+DNase, P+L-DNase, and P-L+DNase; n = 12). Biofilm analysis included quantification of extracellular matrix components (water-soluble and insoluble proteins and polysaccharides, and extracellular DNA), and biomass (total and insoluble), as well as enumeration of colony-forming units. The data were analyzed using three-way analysis of variance with Bonferroni's post-hoc test.

RESULTS

The DNase treatment combined with aPDT showed a reduction of 1.92, 1.65, and 1.29 log₁₀ of cell viability compared with untreated controls for ATCC 96901, R14, and R70 strains, respectively. It also reduced extracellular matrix contents of water-soluble polysaccharides (36.3%) and extracellular DNA (72.3%), as well as insoluble biomass content (43.3%).

CONCLUSION

The three strains showed similar behavior when treated with DNase, and the extracellular matrix components were affected, improving the effectiveness of antimicrobial photodynamic therapy.

Staphylococcus aureus biofilm inhibition by high voltage prick electrostatic field (HVPEF) and the mechanism investigation

The study was to investigate the inhibitory effect and mechanism of high voltage prick electrostatic field (HVPEF) on Staphylococcus aureus biofilms. Results showed that HVPEF effectively inactivated 24-h and 48-h established S. aureus biofilms, and the effect was verified on different food-contact materials. Confocal laser scanning microscopy and scanning electron microscopy analysis suggested that HVPEF disintegrated the established biofilms by killing the embedded bacteria, but it hardly reduced the bacteria adhesion. HVPEF also effectively inhibit the formation of S. aureus biofilms, the effects varied with electric voltage, treatment time and biofilm culture conditions. The direct effect of HVPEF on planktonic S. aureus was a possible mode of biofilm formation inhibition. HVPEF also suppressed biofilm formation by reducing the release of key compositions of extracellular polymeric substance, including extracellular DNA (eDNA), protein and polysaccharide intercellular adhesion (PIA), and regulating the expression of biofilm formation related genes (icaA, ebh, cidA, sarA, icaR and sigB). We propose HVPEF as a novel method to inhibit bacteria biofilm, based on the results, HVPEF has positive effects to prevent biofilm-associated contamination of S. aureus.

Small-Molecule Compound SYG-180-2-2 to Effectively Prevent the Biofilm Formation of Methicillin-Resistant Staphylococcus aureus

The resistance of methicillin-resistant Staphylococcus aureus (MRSA) has augmented due to the abuse of antibiotics, bringing about difficulties in the treatment of infection especially with the formation of biofilm. Thus, it is essential to develop antimicrobials. Here we synthesized a novel small-molecule compound, which we termed SYG-180-2-2 (C₂₁H₁₆N₂OSe), that had antibiofilm activity. The aim of this study was to demonstrate the antibiofilm effect of SYG-180-2-2 against clinical MRSA isolates at a subinhibitory concentration (4 μg/ml). In this study, it was showed that significant suppression in biofilm formation occurred with SYG-180-2-2 treatment, the inhibition ranged between 65.0 and 85.2%. Subsequently, confocal laser scanning microscopy and a bacterial biofilm metabolism activity assay further demonstrated that SYG-180-2-2 could suppress biofilm. Additionally, SYG-180-2-2 reduced bacterial adhesion and polysaccharide intercellular adhesin (PIA) production. It was found that the expression of icaA and other biofilm-related genes were downregulated as evaluated by RT-qPCR. At the same time, icaR and codY were upregulated when biofilms were treated with SYG-180-2-2. Based on the above results, we speculate that SYG-180-2-2 inhibits the formation of biofilm by affecting cell adhesion and the expression of genes related to PIA production. Above all, SYG-180-2-2 had no toxic effects on human normal alveolar epithelial cells BEAS-2B. Collectively, the small-molecule compound SYG-180-2-2 is a safe and effective antibacterial agent for inhibiting MRSA biofilm.

Exosomes as Powerful Engines in Cancer: Isolation, Characterization and Detection Techniques

Exosomes, powerful extracellular nanovesicles released from almost all types of living cells, are considered the communication engines (messengers) that control and reprogram physiological pathways inside target cells within a community or between different communities. The cell-like structure of these extracellular vesicles provides a protective environment for their proteins and DNA/RNA cargos, which serve as biomarkers for many malicious diseases, including infectious diseases and cancers. Cancer-derived exosomes control cancer metastasis, prognosis, and development. In addition to the unique structure of exosomes, their nanometer size and tendency of interacting with cells makes them a viable novel drug delivery solution. In recent years, numerous research efforts have been made to quantify and characterize disease-derived exosomes for diagnosis, monitoring, and therapeutic purposes. This review aims to (1) relate exosome biomarkers to their origins, (2) focus on current isolation and detection methods, (3) discuss and evaluate the proposed technologies deriving from exosome research for cancer treatment, and (4) form a conclusion about the prospects of the current exosome research.

Short-chain fatty acids inhibit the biofilm formation of Streptococcus gordonii through negative regulation of competence-stimulating peptide signaling pathway

Streptococcus gordonii, a Gram-positive commensal bacterium, is an opportunistic pathogen closely related to initiation and progression of various oral diseases, such as periodontitis and dental caries. Its biofilm formation is linked with the development of such diseases by enhanced resistance against antimicrobial treatment or host immunity. In the present study, we investigated the effect of short-chain fatty acids (SCFAs) on the biofilm formation of S. gordonii. SCFAs, including sodium acetate (NaA), sodium propionate (NaP), and sodium butyrate (NaB), showed an effective inhibitory activity on the biofilm formation of S. gordonii without reduction in bacterial growth. SCFAs suppressed S. gordonii biofilm formation at early time points whereas SCFAs did not affect its preformed biofilm. A quorum-sensing system mediated by competence-stimulating peptide (CSP) is known to regulate biofilm formation of streptococci. Interestingly, SCFAs substantially decreased mRNA expression of comD and comE, which are CSP-sensor and its response regulator responsible for CSP pathway, respectively. Although S. gordonii biofilm formation was enhanced by exogenous synthetic CSP treatment, such effect was not observed in the presence of SCFAs. Collectively, these results suggest that SCFAs have an anti-biofilm activity on S. gordonii through inhibiting comD and comE expression which results in negative regulation of CSP quorum-sensing system. SCFAs could be an effective anti-biofilm agent against S. gordonii for the prevention of oral diseases.

New Perspectives on Old and New Therapies of Staphylococcal Skin Infections: The Role of Biofilm Targeting in Wound Healing

Among the most common complications of both chronic wound and surgical sites are staphylococcal skin infections, which slow down the wound healing process due to various virulence factors, including the ability to produce biofilms. Furthermore, staphylococcal skin infections are often caused by methicillin-resistant Staphylococcus aureus (MRSA) and become a therapeutic challenge. The aim of this narrative review is to collect the latest evidence on old and new anti-staphylococcal therapies, assessing their anti-biofilm properties and their effect on skin wound healing. We considered antibiotics, quorum sensing inhibitors, antimicrobial peptides, topical dressings, and antimicrobial photo-dynamic therapy. According to our review of the literature, targeting of biofilm is an important therapeutic choice in acute and chronic infected skin wounds both to overcome antibiotic resistance and to achieve better wound healing.

Integration of metabolomics and transcriptomics indicates changes in MRSA exposed to terpinen-4-ol

Background

This study investigated the effects of terpinen-4-ol on methicillin-resistant Staphylococcus aureus (MRSA) and its biofilm, and the possible mechanisms governing this effect.

Results

We observed that terpinen-4-ol has good antibacterial activity and inhibits the formation of MRSA biofilm. The MIC and MBC values for terpinen-4-ol against S. aureus were 0.08% ~ 0.32%. And terpinen-4-ol at 0.32% could kill all bacteria and clear all biofilms. Untargeted metabolomic and transcriptomic analyses showed that terpinen-4-ol strongly inhibited DNA and RNA biosynthesis in MRSA at 2 h after treatment by affecting genes and metabolites related to purine and pyrimidine metabolic pathways. Some differential genes which play important roles in DNA synthesis and the production of eDNA from biofilm exposed to terpinen-4-ol was also significantly decreased compared with that of the control.

Conclusions

Terpinen-4-ol has good antibacterial activity and significantly inhibits the formation of MRSA biofilm by inhibiting purine and pyrimidine metabolism.

Combined an acoustic pressure simulation of ultrasonic radiation and experimental studies to evaluate control efficacy of high-intensity ultrasound against Staphylococcus aureus biofilm

This study evaluated efficacy of high-intensity ultrasound (HIU) on controlling or stimulating Staphylococcus aureus biofilm. Acoustic pressure distribution on the surface of glass slide cultivated S. aureus biofilm was first simulated as a standardized parameter to reflect sono-effect. When the power of HIU was 240 W with acoustic pressure of -1.38×105 Pa, a reasonably high clearance rate of S. aureus biofilm was achieved (96.02%). As an all-or-nothing technique, the HIU did not cause sublethal or injury of S. aureus but inactivate the cell directly. A further evaluation of HIU-induced stimulation of biofilm was conducted at a low power level (i.e. 60 W with acoustic pressure of -6.91×104 Pa). The low-power-long-duration HIU treatment promoted the formation of S. aureus biofilm and enhanced its resistance as proved by transcriptional changes of genes in S. aureus, including up-regulations of rbf, sigB, lrgA, icaA, icaD, and down-regulation of icaR. These results indicate that the choose of input power is determined during the HIU-based cleaning and processing. Otherwise, the growth of S. aureus and biofilm formation are stimulated when treats by an insufficiently high power of HIU.