Epidermidis Biofilm Research Articles

Anti-infective DNase I coatings on polydopamine functionalized titanium surfaces by alternating current electrophoretic deposition

Implant-associated infections (IAIs) can cause serious problems due to the difficult-to-treat nature of the biofilms formed on the implant surface. In mature biofilms, the matrix, which consists of polysaccharides, proteins, lipids and extracellular DNA (eDNA), forms a protective environment for the residing bacteria, shielding them from antibiotics and host defenses. Recently, the indirect prevention of biofilm growth through the degradation of eDNA using an enzyme, such as deoxyribonuclease (DNase) I, has gained attention and is regarded as a promising strategy in the battle against IAIs. In this study, coatings of DNase I were applied on titanium implant materials and their anti-infective properties were investigated. First, the effectiveness of alternating current electrophoretic deposition (AC-EPD) as a novel processing route to apply DNase I on titanium was examined and compared with the commonly applied diffusion methodology (i.e. classic dipping). For the same processing time, the use of AC-EPD in combination with a polydopamine (PDA) coupling chemistry on the titanium electrode surface significantly increased the protein deposition yield as compared to classic dipping, thereby yielding homogeneous coatings with a thickness of 12.8 nm and an average surface roughness, Sa, of ∼20 nm. X-ray photoelectron spectroscopy confirmed the presence of peptide bonds on all DNase-coated substrates. Time-of-flight secondary ion mass spectrometry detected a more dense DNase I layer in the case of AC-EPD for electrodes coupled as anode during the high-amplitude half cycle of the AC signal. The enzyme activity, release kinetics, and shelf life of DNase I coatings were monitored in real-time using a quantitative qDNase assay. The activity of DNase I coatings produced using AC-EPD was three time higher than for coatings prepared by classic dipping. For both deposition methods, a high initial burst release was observed within the first 2 h, while some activity was still retained at the surface after 7 days. This can be explained by the stable attachment of a small fraction of DNase to the surface through covalent bonding to the PDA layer, while superimposing DNase deposits were only loosely bound and therefore released rapidly upon immersion in the medium. Interestingly, coatings prepared with AC-EPD exhibited a prolonged, gradual release of DNase activity. The AC-EPD DNase coatings significantly reduced biofilm formation of both Staphylococcus epidermidis and Pseudomonas aeruginosa up to 20 h, whereas DNase coatings prepared by short classic dipping only reduce S. epidermidis biofilm formation, and this to a lesser extent as compared to AC-EPD DNase coatings. Overall, this study indicates that AC-EPD allows to rapidly concentrate DNase I on PDA-functionalized titanium, while maintaining the enzyme activity and anti-infective ability. This highlights the potential of AC-EPD as a time-efficient coating strategy (as opposed to the much slower dip-coating methodologies) for bioactive molecules in a wide variety of biomedical applications.

Moxifloxacin Liposomes: Effect of Liposome Preparation Method on Physicochemical Properties and Antimicrobial Activity against Staphylococcus epidermidis.

The aim of this study was the development of optimal sustained-release moxifloxacin (MOX)-loaded liposomes as intraocular therapeutics of endophthalmitis. Two methods were compared for the preparation of MOX liposomes; the dehydration–rehydration (DRV) method and the active loading method (AL). Numerous lipid-membrane compositions were studied to determine the potential effect on MOX loading and retention in liposomes. MOX and phospholipid contents were measured by HPLC and a colorimetric assay for phospholipids, respectively. Vesicle size distribution and surface charge were measured by DLS, and morphology was evaluated by cryo-TEM. The AL method conferred liposomes with higher MOX encapsulation compared to the DRV method for all the lipid compositions used. Cryo-TEM showed that both liposome types had round vesicular structure and size around 100–150 nm, while a granular texture was evident in the entrapped aqueous compartments of most AL liposomes, but substantially less in DRV liposomes; X-ray diffraction analysis demonstrated slight crystallinity in AL liposomes, especially the ones with highest MOX encapsulation. AL liposomes retained MOX for significantly longer time periods compared to DRVs. Lipid composition did not affect MOX release from DRV liposomes but significantly altered drug loading/release in AL liposomes. Interestingly, AL liposomes demonstrated substantially higher antimicrobial potential towards S. epidermidis growth and biofilm susceptibility compared to corresponding DRV liposomes, indicating the importance of MOX retention in liposomes on their activity. In conclusion, the liposome preparation method/type determines the rate of MOX release from liposomes and modulates their antimicrobial potential, a finding that deserves further in vitro and in vivo exploitation.

MazEF Homologue Has a Minor Role in Staphylococcus epidermidis 1457 Virulence Potential.

Staphylococcus epidermidis biofilm cells are characterized by increased antimicrobial tolerance and improved ability to evade host immune system defenses. These features are, in part, due to the presence of viable but non-culturable (VBNC) cells. A previous study identified genes potentially involved in VBNC cells formation in S. epidermidis biofilms, among which SERP1682/1681 raised special interest due to their putative role as a toxin–antitoxin system of the mazEF family. Herein, we constructed an S. epidermidis mutant lacking the mazEF genes homologues and determined their role in (i) VBNC state induction during biofilm formation, (ii) antimicrobial susceptibility, (iii) survival in human blood and plasma, and (iv) activation of immune cells. Our results revealed that mazEF homologue did not affect the proportion of VBNC cells in S. epidermidis 1457, refuting the previous hypothesis that mazEF homologue could be linked with the emergence of VBNC cells in S. epidermidis biofilms. Additionally, mazEF homologue did not seem to influence key virulence factors on this strain, since its deletion did not significantly affect the mutant biofilm formation capacity, antimicrobial tolerance or the response by immune cells. Surprisingly, our data suggest that mazEF does not behave as a toxin–antitoxin system in S. epidermidis strain 1457, since no decrease in the viability and culturability of bacteria was found when only the mazF toxin homologue was being expressed.

Involvement of the Iron-Regulated Loci hts and fhuC in Biofilm Formation and Survival of Staphylococcus epidermidis within the Host.

ABSTRACTStaphylococcus epidermidis is a major nosocomial pathogen with a remarkable ability to persist on indwelling medical devices through biofilm formation. Nevertheless, it remains intriguing how this process is efficiently achieved under the host’s harsh conditions, where the availability of nutrients, such as essential metals, is scarce. Following our previous identification of two iron-regulated loci putatively involved in iron transport, hts and fhuC, we assessed here their individual contribution to both bacterial physiology and interaction with host immune cells. Single deletions of the hts and fhuC loci led to marked changes in the cell iron content, which were partly detrimental for planktonic growth and strongly affected biofilm formation under iron-restricted conditions. Deletion of each of these two loci did not lead to major changes in S. epidermidis survival within human macrophages or in an ex vivo human blood model of bloodstream infection. However, the lack of either hts or fhuC loci significantly impaired bacterial survival in vivo in a murine model of bacteremia. Collectively, this study establishes, for the first time, the pivotal role of the iron-regulated loci hts and fhuC in S. epidermidis biofilm formation and survival within the host, providing relevant information for the development of new targeted therapeutics against this pathogen.IMPORTANCE Staphylococcus epidermidis is one of the most important nosocomial pathogens and a major cause of central line-associated bloodstream infections. Once in the bloodstream, this bacterium must surpass severe iron restriction in order to survive and establish infection. Surprisingly, very little is known about the iron acquisition mechanisms in this species. This study represents the first report on the involvement of the S. epidermidis iron-regulated loci hts and fhuC in biofilm formation under host relevant conditions and, most importantly, in survival within the host. Ultimately, these findings highlight iron acquisition and these loci in particular, as potential targets for future therapeutic strategies against biofilm-associated S. epidermidis infections.

Molecular docking and simulation of IcaC protein as O-succinyltransferase function in staphylococcus epidermidis biofilm formation.

Intercellular adhesion (IcaADBC) operon is necessary for PNAG (Polyβ-1,6-N-acetyl-D-glucosamine) biosynthesis of biofilm formation in Staphylococcus epidermidis. IcaC protein has a wide range of functions in terms of growth phase variation, migration, transposon insertion, PNAG modification, biofilm formation. Unusual TTTA signature motifs were identified from nucleotide sequence. Asparagine-linked glycosylation consensus motifs were identified at position 169 and 240. S. epidermidis was a close evolutionary association with S. haemolyticus and other Staphylococcus spp. Due to the non-availability of crystal structure, protein threading procedure was selected for constructing a full length IcaC three-dimensional structure. QMEANBrane structure quality assessment with model scores −100000 range within predicted integral membrane structure. IcaC motif constitutes 18 transmembrane helix, 37 helix-helix interaction, 8 beta turn, 2 gamma turn. Binding free energy was calculated with their succinate ligand docking form hydrogen bond with critical amino acids showed ΔG score −2.574 ​kJ/mol using Schrödinger. Serine (Ser96), Glutamic acid (Glu99), Tryptophan (Trp191) were active site amino acids form the catalytic core required for O-succinyltransferase function. Molecular dynamics simulation (MDS) was performed to evaluate the stability of IcaC protein and IcaC-Succinate binding complexes with the active site amino acids throughout trajectories captured with time scale 100 ns simulation period using GROMACS 4.5.

A quinoline alkaloid potentially modulates the amyloidogenic structural transitions of the biofilm scaffolding small basic protein

Bacterial biofilm formation by communities of opportunistic bacterial pathogens like Staphylococcus epidermidis is regarded as the primary virulence mechanism facilitating the spread of detrimental nosocomial and implant-associated infections. An 18-kDa small basic protein (Sbp) and its amyloid fibrils account for strengthening the biofilm architecture and scaffolding the S. epidermidis biofilm matrix. Our study reports systematic analysis of the amyloidogenic structural transitions of Sbp and predicts the amyloid core of the protein which may trigger misfolding and aggregation. Herein, we report the novel amyloid inhibitory potential of Camptothecin, a quinoline alkaloid which binds stably to Sbp monomers and redirects the formation of unstructured regions further destabilizing the protein. Molecular dynamics simulations reveal that Camptothecin averts β-sheet transitions, interrupts with electrostatic interactions and disrupts the intermolecular hydrophobic associations between the exposed hydrophobic amyloidogenic regions of Sbp. Collectively, our study puts forward the first report detailing the heteromolecular associations and amyloid modulatory effects of Camptothecin which may serve as a structural scaffold for the tailored designing of novel drugs targeting the S. epidermidis biofilm matrix. Communicated by Ramaswamy H. Sarma

Biofilm Propensity of Staphylococcus Aureus Skin Isolates Is Associated With Increased Atopic Dermatitis Severity and Barrier Dysfunction in the MPAACH Pediatric Cohort

Atopic dermatitis (AD) patients are commonly colonized with Staphylococcus aureus, and staphylococcal biofilms have been described in adult AD lesions. The commensal Staphylococcus epidermidis can antagonize S aureus, but its role in AD is unclear. These investigators sought to characterize S aureus and S epidermidis colonization and biofilm propensity and determine their association with AD severity, barrier function, and epidermal gene expression in an early-life cohort of children with AD.The Mechanisms of Progression of Atopic Dermatitis to Asthma in Children (MPAACH) cohort consists of children aged 1 to 2 years in the greater Cincinnati, Ohio area with either physician-diagnosed AD or a positive parental response to all 3 questions on the Children’s Eczema Questionnaire.A total of 500 children are being enrolled. The current study was focused on the first 400 MPAACH participants. Demographic, environmental, asthma trigger, and personal and family allergy and asthma history data were compiled. AD severity was documented with the Scoring of Atopic Dermatitis scale. Topical medications were withheld the night before the visit. The biofilm propensity of staphylococcal isolates was assessed by crystal violet assays. Gene expression of filaggrin and antimicrobial alarmins S100A8 and S100A9 were measured in keratinocyte RNA extracted from skin tape strips. Staphylococcal biofilms were visualized with scanning electron microscopy.Among the entire 400 children, 26.5% had positive cultures for S aureus, whereas 71% were positive for S epidermidis. A total of 62% of staphylococcal isolates formed moderate or strong biofilms, whereas 68% of those co-colonized with both staphylococcal species exhibited strains that formed cooperative mixed-species biofilms. Scanning electron microscopy verified presence of biofilms. S aureus strains showing higher relative biofilm propensity compared with S epidermidis were associated with increased AD severity and increased lesional and nonlesional transepidermal water loss. Biofilm propensity was associated with decreased FLG expression, which otherwise encodes filaggrin, a structural protein essential to prevent water loss.Collectively, these data suggest that, although S. aureus colonization is associated with increased AD severity, it is the ability of S. aureus to form strong biofilms and the balance between biofilm-forming S. aureus and S epidermidis strains that are particularly important factors affecting AD severity and barrier dysfunction.Biofilms are important in many complex disease processes, and atopic dermatitis appears to be no exception. Whether through genetic (eg, allergy and filaggrin mutations), environmental, or other factors, the altered skin barrier predisposes to S aureus colonization. This jibes with the common clinical observation that acute AD flares are often responsive to a course of both systemic and topical antistaphylococcal therapy while aggressively employing moisturizing measures.

Fighting Staphylococcus epidermidis Biofilm-Associated Infections: Can Iron Be the Key to Success?

Staphylococcus epidermidis is one of the most important commensal microorganisms of human skin and mucosae. However, this bacterial species is also the cause of severe infections in immunocompromised patients, specially associated with the utilization of indwelling medical devices, that often serve as a scaffold for biofilm formation. S. epidermidis strains are often multidrug resistant and its association with biofilm formation makes these infections hard to treat. Their remarkable ability to form biofilms is widely regarded as its major pathogenic determinant. Although a significant amount of knowledge on its biofilm formation mechanisms has been achieved, we still do not understand how the species survives when exposed to the host harsh environment during invasion. A previous RNA-seq study highlighted that iron-metabolism associated genes were the most up-regulated bacterial genes upon contact with human blood, which suggested that iron acquisition plays an important role in S. epidermidis biofilm development and escape from the host innate immune system. In this perspective article, we review the available literature on the role of iron metabolism on S. epidermidis pathogenesis and propose that exploiting its dependence on iron could be pursued as a viable therapeutic alternative.

N-Acetyl-l-cysteine-Loaded Nanosystems as a Promising Therapeutic Approach Toward the Eradication of Pseudomonas aeruginosa Biofilms.

Bacterial biofilms are a major health concern, mainly due to their contribution to increased bacterial resistance to well-known antibiotics. The conventional treatment of biofilms represents a challenge, and frequently, eradication is not achieved with long-lasting administration of antibiotics. In this context, the present work proposes an innovative therapeutic approach that is focused on the encapsulation of N-acetyl-l-cysteine (NAC) into lipid nanoparticles (LNPs) functionalized with d-amino acids to target and disrupt bacterial biofilms. The optimized formulations presented a mean hydrodynamic diameter around 200 nm, a low polydispersity index, and a high loading capacity. These formulations were stable under storage conditions up to 6 months. In vitro biocompatibility studies showed a low cytotoxicity effect in fibroblasts and a low hemolytic activity in human red blood cells. Nevertheless, unloaded LNPs showed a higher hemolytic potential than NAC-loaded LNPs, which suggests a safer profile of the latter. The in vitro antibiofilm efficacy of the developed formulations was tested against Staphylococcus epidermidis (Gram-positive) and Pseudomonas aeruginosa (Gram-negative) mature biofilms. The results showed that the NAC-loaded LNPs were ineffective against S. epidermidis biofilms, while a significant reduction of biofilm biomass and bacterial viability in P. aeruginosa biofilms were observed. In a more complex therapeutic approach, the LNPs were further combined with moxifloxacin, revealing a beneficial effect between the LNPs and the antibiotic against P. aeruginosa biofilms. Both alone and in combination with moxifloxacin, unloaded and NAC-loaded LNPs functionalized with d-amino acids showed a great potential to reduce bacterial viability, with no significant differences in the presence or absence of NAC. However, the presence of NAC in NAC-loaded functionalized LNPs shows a safer profile than the unloaded LNPs, which is beneficial for an in vivo application. Overall, the developed formulations present a potential therapeutic approach against P. aeruginosa biofilms, alone or in combination with antibiotics.

Low-molecular weight chitosan enhances antibacterial effect of antibiotics and permeabilizes cytoplasmic membrane of Staphylococcus epidermidis biofilm cells.

This study evaluated the effect of low-molecular weight chitosan on Staphylococcus epidermidis, a common colonizer of joint implants and other prosthetic devices. We have also attempted to elucidate its mechanism of action. Chitosan was found to be effective against both the planktonic and biofilm cells (MIC80 35-40mg/L; MBIC80 40-150mg/L), in contrast to the antibiotics erythromycin and tetracycline with no antibiofilm activity (MBIC80 not found). In combination, chitosan had an additive effect with antibiotics on suspension growth of S. epidermidis (FICi 0.7-1.0), and the combinatory action caused a complete inhibition of biofilm metabolic activity in some cases. In addition, chitosan caused rapid cellular damage and enhanced antihaemolytic activity of tetracycline in combination towards S. epidermidis biofilm cells. Chitosan efficiently inhibited S. epidermidis growth acting via cell membrane damage, yet the extent of antimicrobial and antibiofilm activities was quite strain-specific. It was proved to be a very efficient antimicrobial agent worth further examination as a potent candidate in pharmaceutical research. Apart from antimicrobial activity, it also acted as antivirulence enhancing agent which is a very promising strategy for alternative infectious diseases treatment.

Novel Nitro-Heteroaromatic Antimicrobial Agents for the Control and Eradication of Biofilm-Forming Bacteria

The synthesis and biological activity of several novel nitrothiazole, nitrobenzothiazole, and nitrofuran containing antimicrobial agents for the eradication of biofilm-forming Gram-negative and Gram-positive pathogens is described. Nitazoxanide (NTZ), nitrofurantoin, and furazolidone are commercial antimicrobials which were used as models to show how structural modification improved activity toward planktonic bacteria via minimum inhibitory concentration (MIC) assays and biofilms via minimum biofilm eradication concentration (MBEC) assays. Structure–activity relationship (SAR) studies illustrate the ways in which improvements have been made to the aforementioned antimicrobial agents. It is of particular interest in this regard that the introduction of a chloro substituent at the 5-position of NTZ (analog 1b) resulted in marked activity enhancement, as did the replacement of the 2-acetoxy substituent in the latter compound with a basic amine group (analog 7b). It is also of importance that analog 4a, which is a simple methacrylamide, displayed noteworthy activity against S. epidermidis biofilms. These lead compounds identified to have high activity towards biofilms provide promise as starting points in future pro-drug studies.

EFFECT OF Staphylococcus epidermidis ON Pseudomonas aeruginosa BIOFILM IN MIXED-SPECIES CULTURE

Staphylococcus epidermidis and Pseudomonas aeruginosa, are clinically relevant pathogens that often produce biofilms. To investigate the co-survivability of S. epidermidis and P. aeruginosa in mixed cultures biofilm and planktonic form, it is important to understand more about the interspecies interaction of both species. The interspecies interaction was analyzed using streak and drop agar plate assay, cell viability assay (CFU), spectrophotometry-based method, and microscopic analysis. The findings suggest that both cells and supernatant of P. aeruginosa inhibit the planktonic growth of S. epidermidis. The cell viability result shows that PAO1 biofilm cells were decreased by 88%, and SE biofilm cells were increased by 75% concerning their control. Opposite to the P. aeruginosa, the S. epidermidis biofilm and EPS matrix were found to increase in mixed culture biofilm, which was further confirmed by microscopic analysis. In contrast, differential agar media result shows that the reduction in the biofilm (CFU/ml) of P. aeruginosa is independent of S. epidermidis cells concentration. Finally, the effect of the supernatant on biofilm was investigated, and it found that S. epidermidis biofilm was enhanced while P. aeruginosa biofilm was reduced in the presence of partner bacterial supernatant, which indicated that S. epidermidis in biofilm mode could hinder the biofilm formation of P. aeruginosa. The outcomes show that the culture supernatant of S. epidermidis can be used to prevent P. aeruginosa associated biofilm infections.

Soybeans agroindustrial residues as Staphylococcus epidermidis and S. aureus biofilm inhibitors

The reuse of agroindustrial waste has been the subject of several studies since they present rich chemical composition and their disposal generates costs to industries and harmful potential to the environment. Compounds present in soybean residues may have a potential antibiofilm activity, a property still very little explored in this raw material. The seek for active compounds against biofilms, has been extremely important, since they represent a challenge in clinical and industrial environments. Thus, this study aimed to evaluate the potential antibiofilm and antimicrobial activities of extracts obtained from soybeans processing residues against Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. Antibacterial and antibiofilm activities of two crude extracts were evaluated using absorbance (620 nm), colony-forming units (CFU) counting, and the crystal violet method, respectively. The safety of these compounds was assessed using the alternative model Caenorhabditis elegans. The extract obtained from fragments of the grain and stalks (E1) had its chemical characterization investigated and was submitted fractionation by ultrafiltration. The proteomic and metabolomic analysis of an active fraction was performed using liquid chromatography and mass spectrometry. E1 (4 mg/mL) inhibited 75 % of the S. epidermidis biofilm formation with no inhibition of bacterial growth. Antibiofilm activity of E1 was lost when it was submitted to a heat treatment, while the enzymatic treatment with proteinase K led to a loss of 30 % in the activity of the extract, suggesting that the antibiofilm molecules may be of protein origin. When submitted to the ultrafiltration process, the antibiofilm activity was observed mainly when two fractions (fraction> 50 kDa (R50) and fraction <10 kDa (F10′)) were combined, suggesting that the biological activity is dependent on the combination of the active molecules. The metabolomic analysis of F10′ indicated the presence of flavonoids, lipids, peptides, organic compounds and nucleosides while in the proteomic analysis of R50 a total of 19 proteins were identified. The extract E1 and the active fraction (R50+F10′) showed low toxicity in C. elegans. This work shows that soybeans agroindustrial residues may be a potential source of molecules with activity against bacterial biofilms.

Antimicrobial, antibiofilm, antioxidant, anticancer, and phytochemical composition of the seed extract of Pongamia pinnata.

Ethyl acetate seed extract of Pongamia pinnata displayed the highest antimicrobial potential against all test pathogens and Staphylococcus epidermidis was reported as the most sensitive strain with MIC/MBC 1.56/3.12mgml-1. It inhibited S. epidermidis biofilm 97.43% at MIC and LM as well as FE-SEM micrographs displayed extensive disintegration in biofilm. It showed the highest TPC (1.23 ± 0.04g GAE g-1), TFC (0.95 ± 0.05g CE g-1), and antioxidant activity with IC50 18.47 ± 0.33μgml-1. MTT assay displayed concentration-dependent strong cytotoxicity on K562 cells on the treatment of ethyl acetate extract with an IC50 value of 84.41μgml-1. On the other hand, it showed minute cytotoxicity on normal PBMCs with an IC50 value of 410.14μgml-1. GC-MS analysis revealed that Hexadecanoic acid (35.97%); 2-(1,3-Benzodioxol-5-yl)furo[2,3-h]chromen-4-one (Pongaglabrone) (22.82%); 2,2-Dimethylindane-1,3-dione- (13.05%) were the three major components in ethyl acetate extract. The present investigation showcases ethyl acetate extract as a potent antimicrobial, antibiofilm, antioxidant, and anticancer agent that opens a new avenue for its phytochemicals as a therapeutic agent.

Understanding How Staphylococcal Autolysin Domains Interact With Polystyrene Surfaces.

Biofilms, when formed on medical devices, can cause malfunctions and reduce the efficiency of these devices, thus complicating treatments and serving as a source of infection. The autolysin protein of Staphylococcus epidermidis contributes to its biofilm forming ability, especially on polystyrene surfaces. R2ab and amidase are autolysin protein domains thought to have high affinity to polystyrene surfaces, and they are involved in initial bacterial attachment in S. epidermidis biofilm formation. However, the structural details of R2ab and amidase binding to surfaces are poorly understood. In this study, we have investigated how R2ab and amidase influence biofilm formation on polystyrene surfaces. We have also studied how these proteins interact with polystyrene nanoparticles (PSNPs) using biophysical techniques. Pretreating polystyrene plates with R2ab and amidase domains inhibits biofilm growth relative to a control protein, indicating that these domains bind tightly to polystyrene surfaces and can block bacterial attachment. Correspondingly, we find that both domains interact strongly with anionic, carboxylate-functionalized as well as neutral, non-functionalized PSNPs, suggesting a similar binding interaction for nanoparticles and macroscopic surfaces. Both anionic and neutral PSNPs induce changes to the secondary structure of both R2ab and amidase as monitored by circular dichroism (CD) spectroscopy. These changes are very similar, though not identical, for both types of PSNPs, suggesting that carboxylate functionalization is only a small perturbation for R2ab and amidase binding. This structural change is also seen in limited proteolysis experiments, which exhibit substantial differences for both proteins when in the presence of carboxylate PSNPs. Overall, our results demonstrate that the R2ab and amidase domains strongly favor adsorption to polystyrene surfaces, and that surface adsorption destabilizes the secondary structure of these domains. Bacterial attachment to polystyrene surfaces during the initial phases of biofilm formation, therefore, may be mediated by aromatic residues, since these residues are known to drive adsorption to PSNPs. Together, these experiments can be used to develop new strategies for biofilm eradication, ensuring the proper long-lived functioning of medical devices.

Novel Peptides Targeting the β-Clamp Rapidly Kill Planktonic and Biofilm Staphylococcus epidermidis Both in vitro and in vivo.

Antimicrobial resistance is an increasing threat to global health and challenges the way we treat infections. Peptides containing the PCNA interacting motif APIM (APIM-peptides) were recently shown to bind to the bacterial PCNA homolog, the beta (β)-clamp, and to have both antibacterial and anti-mutagenic activities. In this study we explore the antibacterial effects of these peptides on Staphylococcus epidermidis, a bacterial species commonly found in prosthetic joint infections (PJI). Drug-resistant bacterial isolates from PJIs often lead to difficult-to-treat chronic infections. We show that APIM-peptides have a rapid bactericidal effect which when used at sublethal levels also increase the efficacy of gentamicin. In addition, APIM-peptides reduce development and eliminate already existing S. epidermidis biofilm. To study the potential use of APIM-peptides to prevent PJI, we used an in vivo bone graft model in rats where APIM-peptide, gentamicin, or a combination of the two was added to cement. The bone grafts containing cement with the combination was more effective than cement containing only gentamicin, which is the current standard of care. In summary, these results suggest that APIM-peptides can be a promising new drug candidate for anti-infective implant materials to use in the fight against resistant bacteria and chronic PJI.

Atrial Natriuretic Peptide Affects Skin Commensal Staphylococcus epidermidis and Cutibacterium acnes Dual-Species Biofilms.

The first evidence of the atrial natriuretic peptide (ANP) effect on mono-species and dual-species biofilms of skin commensals Cutibacterium acnes and Staphylococcus epidermidis was obtained in different model systems. Elucidation of the mechanism of action of hormones on the microbial communities of human skin is an important physiological and medical aspect. Under anaerobic conditions, ANP at a concentration of 6.5 × 10−10 M inhibits the growth of S. epidermidis biofilms and stimulates the growth of C. acnes biofilms, and a lesser effect has been demonstrated on planktonic cultures. In biofilms, ANP stimulates aggregation in C. acnes and aggregate dispersion of S. epidermidis, while in S. epidermidis, ANP also stimulates the metabolic activity of cells. Analysis of dual-species biofilms has shown the dominance of S. epidermidis, while ANP increases the ratio of C. acnes biomass in the community. ANP decreases the growth rate of S. epidermidis biofilms and increases that of C. acnes. The effect of ANP is not dependent on the surface type and probably affects other targets in microbial cells. Thus, the potential regulatory effect of human ANP on skin microbe dual-species communities has been shown, and its potential has been demonstrated to change microbiota homeostasis on the skin.

Identification of Eltrombopag as a Repurposing Drug Against Staphylococcus epidermidis and its Biofilms.

Staphylococcus epidermidis is a common cause of nosocomial infections, and readily adheres to medical apparatus to form biofilms consisting of highly resistant persister cells. Owing to the refractory infections caused by S. epidermidis biofilms and persisters in immunosuppressed patients, it is crucial to develop new antimicrobials. In the present study, we analyzed the antimicrobial effects of the thrombopoietin receptor agonist eltrombopag (EP) against S. epidermidis planktonic cells, biofilms, and persister cells. EP was significantly toxic to S. epidermidis with the minimal inhibitory concentration of 8μg/ml, and effectively inhibited the biofilms and persisters in a strain-dependent manner. In addition, EP was only mildly toxic to mammalian cells after 12 to 24h treatment. It also partially synergized with vancomycin against S. epidermidis, which enhanced its antimicrobial effects and reduced its toxicity to mammalian cells. Taken together, EP is a potential antibiotic for treating refractory infections caused by S. epidermidis.

Inhibitory Effects of &lt;i&gt;Escherichia coli&lt;/i&gt; on the Formation and Development of &lt;i&gt;Staphylococcus epidermidis&lt;/i&gt; Biofilm

In the present study, we examined whether a commensal gut bacterium Escherichia coli might prevent the formation and development of the biofilm of Staphylococcus epidermidis, a nosocomial extraintestinal pathogen but not a gut microorganism. When co-cultured with S. epidermidis, E. coli strain ATCC 35218, a non-pathogenic strain, was found to be dominant in the biofilm formed on the surface of wells of a microtiter plate. In addition, E. coli significantly incorporated and grew in a niche preoccupied by S. epidermidis biofilm. Two other E. coli strains (strain K-12 and B) also showed to interfere the biofilm formation by S. epidermidis. In contrast, S. epidermidis could not grow in a niche preoccupied by E. coli biofilm. These results suggest that, through inhibition of the formation and development of the biofilm, E. coli may eliminate S. epidermidis from the gastrointestinal tract.

Titanium-Tantalum Alloy Surface Modification by Hydroxyapatite Layer on TiO2 Nanotubes: Effect on Microbial Activity

Abstract One of the major health security challenges of the 21st century is the occurrence of microbial infections and bacterial complications that could affect 10 million people by 2050. On the biomaterial field, implant metallic currently replaces partial or total body parts and can fail to be integrated into the body due to infections. This study performs two combined surface modifications on Ti-30Ta alloy, in order to obtain an infection-resistance and osseointegration surface on metallic implants to be tested within bacterial biofilm. The Group 1 investigated surface modifications by the anodization process in the electrolyte glycerol + NH4F 0.25% at 30V- 9 hours and annealed in 530°C (5°C/min). The Group 2 underwent the same process as Group 1 and, additionally, the samples were immersed in 0.3 M CaCl2 and 0.5 M Na2HPO4 solutions for hydroxyapatite growth. The substrate was characterized using scanning electron microscopy (SEM), X-ray diffractometer (XRD) and dynamic contact angle. S. epidermidis bacterial adhesion and biofilm formation. The results indicated that the Group 1 shows a higher antimicrobial activity, hydrophilic behavior and potential to be used for metallic implant applications. The Group 2 with the hydroxyapatite film coating did not have an improvement in the antimicrobial response.