Wall teichoic acid substitution with glucose governs phage susceptibility of Staphylococcus epidermidis

The species- and clone-specific susceptibility of Staphylococcus cells for bacteriophages is governed by the structures and glycosylation patterns of wall teichoic acid (WTA) glycopolymers. The glycosylation-dependent phage-WTA interactions in the opportunistic pathogen Staphylococcus epidermidis and in other coagulase-negative staphylococci (CoNS) have remained unknown. We report a new S. epidermidis WTA glycosyltransferase TagE whose deletion confers resistance to siphoviruses such as ΦE72 but enables binding of otherwise unbound podoviruses. S. epidermidis glycerolphosphate WTA was found to be modified with glucose in a tagE-dependent manner. TagE is encoded together with the enzymes PgcA and GtaB providing uridine diphosphate-activated glucose. ΦE72 transduced several other CoNS species encoding TagE homologs, suggesting that WTA glycosylation via TagE is a frequent trait among CoNS that permits interspecies horizontal gene transfer. Our study unravels a crucial mechanism of phage-Staphylococcus interaction and horizontal gene transfer, and it will help in the design of anti-staphylococcal phage therapies.IMPORTANCEPhages are highly specific for certain bacterial hosts, and some can transduce DNA even across species boundaries. How phages recognize cognate host cells remains incompletely understood. Phages infecting members of the genus Staphylococcus bind to wall teichoic acid (WTA) glycopolymers with highly variable structures and glycosylation patterns. How WTA is glycosylated in the opportunistic pathogen Staphylococcus epidermidis and in other coagulase-negative staphylococci (CoNS) species has remained unknown. We describe that S. epidermidis glycosylates its WTA backbone with glucose, and we identify a cluster of three genes responsible for glucose activation and transfer to WTA. Their inactivation strongly alters phage susceptibility patterns, yielding resistance to siphoviruses but susceptibility to podoviruses. Many different CoNS species with related glycosylation genes can exchange DNA via siphovirus ΦE72, suggesting that glucose-modified WTA is crucial for interspecies horizontal gene transfer. Our finding will help to develop antibacterial phage therapies and unravel routes of genetic exchange.

Staphylococcus epidermidis bacteriocin A37 kills natural competitors with a unique mechanism of action

Many bacteria produce antimicrobial compounds such as lantibiotics to gain advantage in the competitive natural environments of microbiomes. Epilancins constitute an until now underexplored family of lantibiotics with an unknown ecological role and unresolved mode of action. We discovered production of an epilancin in the nasal isolate Staphylococcus epidermidis A37. Using bioinformatic tools, we found that epilancins are frequently encoded within staphylococcal genomes, highlighting their ecological relevance. We demonstrate that production of epilancin A37 contributes to Staphylococcus epidermidis competition specifically against natural corynebacterial competitors. Combining microbiological approaches with quantitative in vivo and in vitro fluorescence microscopy and cryo-electron tomography, we show that A37 enters the corynebacterial cytoplasm through a partially transmembrane-potential-driven uptake without impairing the cell membrane function. Upon intracellular aggregation, A37 induces the formation of intracellular membrane vesicles, which are heavily loaded with the compound and are essential for the antibacterial activity of the epilancin. Our work sheds light on the ecological role of epilancins for staphylococci mediated by a mode of action previously unknown for lantibiotics.

Commensal production of a broad-spectrum and short-lived antimicrobial peptide polyene eliminates nasal Staphylococcus aureus

Antagonistic bacterial interactions often rely on antimicrobial bacteriocins, which attack only a narrow range of target bacteria. However, antimicrobials with broader activity may be advantageous. Here we identify an antimicrobial called epifadin, which is produced by nasal Staphylococcus epidermidis IVK83. It has an unprecedented architecture consisting of a non-ribosomally synthesized peptide, a polyketide component and a terminal modified amino acid moiety. Epifadin combines a wide antimicrobial target spectrum with a short life span of only a few hours. It is highly unstable under in vivo-like conditions, potentially as a means to limit collateral damage of bacterial mutualists. However, Staphylococcus aureus is eliminated by epifadin-producing S. epidermidis during co-cultivation in vitro and in vivo, indicating that epifadin-producing commensals could help prevent nasal S. aureus carriage. These insights into a microbiome-derived, previously unknown antimicrobial compound class suggest that limiting the half-life of an antimicrobial may help to balance its beneficial and detrimental activities.

Electrogenic Staphylococcus epidermidis colonizes nasal cavities and alleviates IL-6 progression induced by the SARS2-CoV nucleocapsid protein

AIM

Certain probiotic bacteria have been shown to possess an immunomodulatory effect and a protective effect on influenza infections. Using the Staphylococcus epidermidis K1 colonized mice model, we assessed the effect of nasal administration of glycerol or flavin mononucleotide (FMN) on the production of interleukin (IL)-6 mediated by the severe acute respiratory syndrome coronavirus 2 (SARS2-CoV) nucleocapsid protein (NPP).

METHODS AND RESULTS

FMN, one of the key electron donors for the generation of electricity facilitated by S. epidermidis ATCC 12228, was detected in the glycerol fermentation medium. Compared to the S. epidermidis ATCC 12228, the S. epidermidis K1 isolate showed significant expression of the electron transfer genes, including pyruvate dehydrogenase (pdh), riboflavin kinase (rk), 1,4-dihydroxy-2-naphthoate octaprenyltransferase (menA), and type II NADH quinone oxidoreductase (ndh2). Institute of cancer research (ICR) mice were intranasally administered with S. epidermidis K1 with or without pretreatment with riboflavin kinase inhibitors, then nasally treated with glycerol or FMN before inoculating the NPP. Furthermore, J774A.1 macrophages were exposed to NPP serum and then treated with NPP of SARS2-CoV. The IL-6 levels in the bronchoalveolar lavage fluid (BALF) of mice and macrophages were quantified using a mouse IL-6 enzyme-linked immunosorbent assay kit.

CONCLUSIONS

Here, we report that nasal administration of NPP strongly elevates IL-6 levels in both BALF and J774A.1 macrophages. It is worth noting that NPP-neutralizing antibodies can decrease IL-6 levels in macrophages. The nasal administration of glycerol or FMN to S. epidermidis K1-colonized mice results in a reduction of NPP-induced IL-6 production.

Staphylococcal Periscope proteins Aap, SasG, and Pls project noncanonical legume-like lectin adhesin domains from the bacterial surface

Staphylococcus aureus and Staphylococcus epidermidis are frequently associated with medical device infections that involve establishment of a bacterial biofilm on the device surface. Staphylococcal surface proteins Aap, SasG, and Pls are members of the Periscope Protein class and have been implicated in biofilm formation and host colonization; they comprise a repetitive region ("B region") and an N-terminal host colonization domain within the "A region," predicted to be a lectin domain. Repetitive E-G5 domains (as found in Aap, SasG, and Pls) form elongated "stalks" that would vary in length with repeat number, resulting in projection of the N-terminal A domain variable distances from the bacterial cell surface. Here, we present the structures of the lectin domains within A regions of SasG, Aap, and Pls and a structure of the Aap lectin domain attached to contiguous E-G5 repeats, suggesting the lectin domains will sit at the tip of the variable length rod. We demonstrate that these isolated domains (Aap, SasG) are sufficient to bind to human host desquamated nasal epithelial cells. Previously, proteolytic cleavage or a deletion within the A domain had been reported to induce biofilm formation; the structures suggest a potential link between these observations. Intriguingly, while the Aap, SasG, and Pls lectin domains bind a metal ion, they lack the nonproline cis peptide bond thought to be key for carbohydrate binding by the lectin fold. This suggestion of noncanonical ligand binding should be a key consideration when investigating the host cell interactions of these bacterial surface proteins.

Evaluation of the Effects of Ag, Cu, ZnO and TiO2 Nanoparticles on the Expression Level of Oxidative Stress-Related Genes and the Activity of Antioxidant Enzymes in Escherichia coli, Bacillus cereus and Staphylococcus epidermidis

Although the molecular response of bacteria exposed to metal nanoparticles (NPs) is intensively studied, many phenomena related to their survival, metal uptake, gene expression and protein production are not fully understood. Therefore, this work aimed to study Ag-NPs, Cu-NPs, ZnO-NPs and TiO₂-NPs-induced alterations in the expression level of selected oxidative stress-related genes in connection with the activity of antioxidant enzymes: catalase (CAT), peroxidase (PER) and superoxide dismutase (SOD) in Escherichia coli, Bacillus cereus and Staphylococcus epidermidis. The methodology used included: the extraction of total RNA and cDNA synthesis, the preparation of primers for selected housekeeping and oxidative stress genes, RT-qPCR reaction and the measurements of CAT, PER and SOD activities. It was established that the treatment of E. coli and S. epidermidis with NPs resulted mainly in the down-regulation of targeted genes, whilst the up-regulation of genes was confirmed in B. cereus. The greatest differences in the relative expression levels of tested genes occurred in B. cereus and S. epidermidis treated with TiO₂-NPs, while in E. coli, they were observed under ZnO-NPs exposure. The changes found were mostly related to the expression of genes encoding proteins with PER and CAT-like activity. Among NPs, ZnO-NPs and Cu-NPs increased the activity of antioxidants in E. coli and B. cereus. In turn, TiO₂-NPs had a major effect on enzymes activity in S. epidermidis. Considering all of the collected results for tested bacteria, it can be emphasised that the impact of NPs on the antioxidant system functioning was dependent on their type and concentration.

Insight into the Antibacterial Activity of Selected Metal Nanoparticles and Alterations within the Antioxidant Defence System in Escherichia coli, Bacillus cereus and Staphylococcus epidermidis

The antimicrobial activity of nanoparticles (NPs) is a desirable feature of various products but can become problematic when NPs are released into different ecosystems, potentially endangering living microorganisms. Although there is an abundance of advanced studies on the toxicity and biological activity of NPs on microorganisms, the information regarding their detailed interactions with microbial cells and the induction of oxidative stress remains incomplete. Therefore, this work aimed to develop accurate oxidation stress profiles of Escherichia coli, Bacillus cereus and Staphylococcus epidermidis strains treated with commercial Ag-NPs, Cu-NPs, ZnO-NPs and TiO2-NPs. The methodology used included the following determinations: toxicological parameters, reactive oxygen species (ROS), antioxidant enzymes and dehydrogenases, reduced glutathione, oxidatively modified proteins and lipid peroxidation. The toxicological studies revealed that E. coli was most sensitive to NPs than B. cereus and S. epidermidis. Moreover, NPs induced the generation of specific ROS in bacterial cells, causing an increase in their concentration, which further resulted in alterations in the activity of the antioxidant defence system and protein oxidation. Significant changes in dehydrogenases activity and elevated lipid peroxidation indicated a negative effect of NPs on bacterial outer layers and respiratory activity. In general, NPs were characterised by very specific nano-bio effects, depending on their physicochemical properties and the species of microorganism.

Short chain fatty acids produced by Cutibacterium acnes inhibit biofilm formation by Staphylococcus epidermidis

Biofilm formation by bacterial pathogens is associated with numerous human diseases and can confer resistance to both antibiotics and host defenses. Many strains of Staphylococcus epidermidis are capable of forming biofilms and are important human pathogens. Since S. epidermidis coexists with abundant Cutibacteria acnes on healthy human skin and does not typically form a biofilm in this environment, we hypothesized that C. acnes may influence biofilm formation of S. epidermidis. Culture supernatants from C. acnes and other species of Cutibacteria inhibited S. epidermidis but did not inhibit biofilms by Pseudomonas aeruginosa or Bacillus subtilis, and inhibited biofilms by S. aureus to a lesser extent. Biofilm inhibitory activity exhibited chemical properties of short chain fatty acids known to be produced from C. acnes. The addition of the pure short chain fatty acids propionic, isobutyric or isovaleric acid to S. epidermidis inhibited biofilm formation and, similarly to C. acnes supernatant, reduced polysaccharide synthesis by S. epidermidis. Both short chain fatty acids and C. acnes culture supernatant also increased sensitivity of S. epidermidis to antibiotic killing under biofilm-forming conditions. These observations suggest the presence of C. acnes in a diverse microbial community with S. epidermidis can be beneficial to the host and demonstrates that short chain fatty acids may be useful to limit formation of a biofilm by S. epidermidis.

Detection of the agr System and Resistance to Antimicrobials in Biofilm-Producing S. epidermidis

The ability of Staphylococcus epidermidis to produce virulence factors, such as biofilm, added to its increased resistance to antimicrobials can cause infections that are difficult to treat. Many staphylococcal virulence factors are under the control of the accessory gene regulator (agr). The objective of this study was to establish the agr locus and susceptibility of biofilm-producing S. epidermidis specimens to antimicrobial agents, through PCR reactions, reverse transcription polymerase chain reaction (RT-PCR), and the determination of minimum inhibitory concentration (MIC), and to analyze the clonal profile of 300 strains isolated from blood culture specimens from inpatients at a University Hospital in Brazil, over a 20-year period by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) techniques. The ica operon expression was shown in 83.6% strains, bhp gene in 11.5%, and aap gene in 32.8%. Oxacillin resistance was detected in 90.1%, while 4.9% showed tigecycline resistance, and intermediate resistance to quinupristin/dalfopristin was identified in 0.4%. Clonal profile determination showed 11 clusters, with the ST2 type determined as the major cluster. The S. epidermidis biofilm producer demonstrated a predominance of agr I locus, oxacillin resistance, and SCCmec III as well as the potential dissemination of pathogenic clones in hospital settings over long periods.

Psoriasis and Antimicrobial Peptides

Psoriasis is a systemic inflammatory disease caused by crosstalk between various cells such as T cells, neutrophils, dendritic cells, and keratinocytes. Antimicrobial peptides (AMPs) such as β-defensin, S100, and cathelicidin are secreted from these cells and activate the innate immune system through various mechanisms to induce inflammation, thus participating in the pathogenesis of psoriasis. In particular, these antimicrobial peptides enhance the binding of damage-associated molecular patterns such as self-DNA and self-RNA to their receptors and promote the secretion of interferon from activated plasmacytoid dendritic cells and keratinocytes to promote inflammation in psoriasis. Neutrophil extracellular traps (NETs), complexes of self-DNA and proteins including LL-37 released from neutrophils in psoriatic skin, induce Th17. Activated myeloid dendritic cells secrete a mass of inflammatory cytokines such as IL-12 and IL-23 in psoriasis, which is indispensable for the proliferation and survival of T cells that produce IL-17. AMPs enhance the production of some of Th17 and Th1 cytokines and modulate receptors and cellular signaling in psoriasis. Inflammation induced by DAMPs, including self-DNA and RNA released due to microinjuries or scratches, and the enhanced recognition of DAMPs by AMPs, may be involved in the mechanism underlying the Köbner phenomenon in psoriasis.

IgY Targeting Bacterial Quorum-Sensing Molecules in Implant-Associated Infections

Background: Implant-associated infections are still a major complication in the field of orthopedics. Bacteria can form biofilms on implant surfaces, making them more difficult to detect and treat. Since standard antibiotic therapy is often impaired in biofilm infections, particular interest is directed towards finding treatment alternatives. Biofilm-formation is a well-organized process during which bacteria communicate via quorum-sensing molecules (QSM). The aim of this study was to inhibit bacterial communication by directing avian IgY against specific QSM. Methods: Chicken were immunized against the following QSM: (1) AtlE, a member of the autolysin family which mediates attachment to a surface in Staphylococcus epidermidis; (2) GroEL, the bacterial heat shock protein; (3) PIA (polysaccharide intercellular adhesion), which is essential for cell–cell adhesion in biofilms. Staphylococcus epidermidis biofilms were grown and inhibition of biofilm-formation by IgYs was evaluated. Additionally, human osteoblasts were cultivated and biocompatibility of IgYs was tested. Results: We were able to demonstrate that all IgYs reduced biofilm-formation, also without prior immunization. Therefore, the response was probably not specific with regard to the QSM. Osteoblasts were activated by all IgYs which was demonstrated by microscopy and an increased release of IL-8. Conclusions: In conclusion, avian IgY inhibits biofilm-formation, though the underlying mechanism is not yet clear. However, adverse effects on local tissue cells (osteoblasts) were also observed.

Phenylpiperazine 5,5-Dimethylhydantoin Derivatives as First Synthetic Inhibitors of Msr(A) Efflux Pump in Staphylococcus epidermidis

Herein, 15 phenylpiperazine 3-benzyl-5,5-dimethylhydantoin derivatives (1-15) were screened for modulatory activity towards Msr(A) efflux pump present in S. epidermidis bacteria. Synthesis, crystallographic analysis, biological studies in vitro and structure-activity relationship (SAR) analysis were performed. The efflux pump inhibitory (EPI) potency was determined by employing ethidium bromide accumulation assay in both Msr(A) efflux pump overexpressed (K/14/1345) and deficient (ATCC 12228) S. epidermidis strains. The series of compounds was also evaluated for the capacity to reduce the resistance of K/14/1345 strain to erythromycin, a known substrate of Msr(A). The study identified five strong modulators for Msr(A) in S. epidermidis. The 2,4-dichlorobenzyl-hydantoin derivative 9 was found as the most potent EPI, inhibiting the efflux activity in K/14/1345 at a concentration as low as 15.63 µM. Crystallography-supported SAR analysis indicated structural properties that may be responsible for the activity found. This study identified the first synthetic compounds able to inhibit Msr(A) efflux pump transporter in S. epidermidis. Thus, the hydantoin-derived molecules found can be an attractive group in search for antibiotic adjuvants acting via Msr(A) transporter.

PEG-8 Laurate Fermentation of Staphylococcus epidermidis Reduces the Required Dose of Clindamycin Against Cutibacterium acnes

The probiotic activity of skin Staphylococcus epidermidis (S. epidermidis) bacteria can elicit diverse biological functions via the fermentation of various carbon sources. Here, we found that polyethylene glycol (PEG)-8 Laurate, a carbon-rich molecule, can selectively induce the fermentation of S. epidermidis, not Cutibacterium acnes (C. acnes), a bacterium associated with acne vulgaris. The PEG-8 Laurate fermentation of S. epidermidis remarkably diminished the growth of C. acnes and the C. acnes-induced production of pro-inflammatory macrophage-inflammatory protein 2 (MIP-2) cytokines in mice. Fermentation media enhanced the anti-C. acnes activity of a low dose (0.1%) clindamycin, a prescription antibiotic commonly used to treat acne vulgaris, in terms of the suppression of C. acnes colonization and MIP-2 production. Furthermore, PEG-8 Laurate fermentation of S. epidermidis boosted the activity of 0.1% clindamycin to reduce the sizes of C. acnes colonies. Our results demonstrated, for the first time, that the PEG-8 Laurate fermentation of S. epidermidis displayed the adjuvant effect on promoting the efficacy of low-dose clindamycin against C. acnes. Targeting C. acnes by lowering the required doses of antibiotics may avoid the risk of creating drug-resistant C. acnes and maintain the bacterial homeostasis in the skin microbiome, leading to a novel modality for the antibiotic treatment of acne vulgaris.

Simultaneous measurement of hydrogen carbonate and acetate anions using biologically active receptor based on azo derivatives of naphthalene

A novel receptor based on azo-derivatives of 1-naphthylamine (2-((E)-((4-chloro-3-(trifluoromethyl)phenyl)imino)methyl)-4-((E)-naphthalene-1-yldiazenyl)phenol(2) abbreviated CTNP was successfully designed and synthesized. Its sensing properties were studied deeply. Systematic studies of CTNP with HCO₃^- and AcO^- anions in DMSO disclosed that there is hydrogen-bonding between CTNP and incoming anions. Significant changes in the visible region of the spectrum, as well as a drastic color change of CTNP from pale yellow to red, observed due to interaction as mentioned earlier. The stoichiometry of [CTNP: HCO₃^- or AcO^-] complexes and association constants determined through Job's method and Benesi-Hildebrand (B-H) plot, respectively. Taking into account the analysis results, CTNP performs the selective recognition of sub-millimolar concentrations of HCO₃^- and AcO^- efficiently. The antifungal activity of the receptor was tested against Aspergillus brasiliensis and Aspergillus niger. CTNP exhibited excellent antifungal activity against both strains. CTNP also represented antibacterial activity against Gram-positive bacteria: Staphylococcus epidermidis. It was cleared that designed receptor can be applied under physiological conditions for a long duration.

Staphylococcus epidermidis Contributes to Healthy Maturation of the Nasal Microbiome by Stimulating Antimicrobial Peptide Production

The composition of the human microbiome profoundly impacts human well-being. However, the mechanisms underlying microbiome maturation are poorly understood. The nasal microbiome is of particular importance as a source of many respiratory infections. Here, we performed a large sequencing and culture-based analysis of the human nasal microbiota from different age groups. We observed a significant decline of pathogenic bacteria before adulthood, with an increase of the commensal Staphylococcus epidermidis. In seniors, this effect was partially reversed. In vitro, many S. epidermidis isolates stimulated nasal epithelia to produce antimicrobial peptides, killing pathogenic competitors, while S. epidermidis itself proved highly resistant owing to its exceptional capacity to form biofilms. Furthermore, S. epidermidis isolates with high antimicrobial peptide-inducing and biofilm-forming capacities outcompeted pathogenic bacteria during nasal colonization in vivo. Our study identifies a pivotal role of S. epidermidis in healthy maturation of the nasal microbiome, which is achieved at least in part by symbiotic cooperation with innate host defense.

Structural insights into the role of the N-terminus in the activation and function of extracellular serine protease from Staphylococcus epidermidis

Extracellular serine protease (Esp) from Staphylococcus epidermidis is a glutamyl endopeptidase that inhibits the growth and formation of S. aureus biofilms. Previously, crystal structures of the matured and active Esp have been determined. Interestingly, many of the staphylococcal glutamyl endopeptidase zymogens, including V8 from Staphylococcus aureus and Esp from S. epidermidis, contain unusually long pro-peptide segments; however, their function is not known. With the aim of elucidating the function of these pro-peptide segments, crystal structures of the Esp zymogen (Pro-Esp) and its variants were determined. It was observed that the N-terminus of the Pro-Esp crystal structure is flexible and is not associated with the main body of the enzyme, unlike in the known active Esp structure. In addition, the loops that border the putative substrate-binding pocket of Pro-Esp are flexible and disordered; the structural components that are responsible for enzyme specificity and efficiency in serine proteases are disordered in Pro-Esp. However, the N-terminal locked Pro-Esp variants exhibit a rigid substrate-binding pocket similar to the active Esp structure and regain activity. These structural studies highlight the role of the N-terminus in stabilizing the structural components responsible for the activity and specificity of staphylococcal glutamyl endopeptidases.

Regulation of cyclic oligoadenylate synthesis by the Staphylococcus epidermidis Cas10-Csm complex

CRISPR-Cas systems are a class of adaptive immune systems in prokaryotes that use small CRISPR RNAs (crRNAs) in conjunction with CRISPR-associated (Cas) nucleases to recognize and degrade foreign nucleic acids. Recent studies have revealed that Type III CRISPR-Cas systems synthesize second messenger molecules previously unknown to exist in prokaryotes, cyclic oligoadenylates (cOA). These molecules activate the Csm6 nuclease to promote RNA degradation and may also coordinate additional cellular responses to foreign nucleic acids. Although cOA production has been reconstituted and characterized for a few bacterial and archaeal Type III systems, cOA generation and its regulation have not been explored for the Staphylococcus epidermidis Type III-A CRISPR-Cas system, a longstanding model for CRISPR-Cas function. Here, we demonstrate that this system performs Mg²⁺-dependent synthesis of 3-6 nt cOA. We show that activation of cOA synthesis is perturbed by single nucleotide mismatches between the crRNA and target RNA at discrete positions, and that synthesis is antagonized by Csm3-mediated target RNA cleavage. Altogether, our results establish the requirements for cOA production in a model Type III CRISPR-Cas system and suggest a natural mechanism to dampen immunity once the foreign RNA is destroyed.

Role of Phenol-Soluble Modulins in Staphylococcus epidermidis Biofilm Formation and Infection of Indwelling Medical Devices

Phenol-soluble modulins (PSMs) are amphipathic, alpha-helical peptides that are secreted by staphylococci in high amounts in a quorum-sensing-controlled fashion. Studies performed predominantly in Staphylococcus aureus showed that PSMs structure biofilms, which results in reduced biofilm mass, while it has also been reported that S. aureus PSMs stabilize biofilms due to amyloid formation. We here analyzed the roles of PSMs in in vitro and in vivo biofilms of Staphylococcus epidermidis, the leading cause of indwelling device-associated biofilm infection. We produced isogenic deletion mutants for every S. epidermidis psm locus and a sequential deletion mutant in which production of all PSMs was abolished. In vitro analysis substantiated the role of all PSMs in biofilm structuring. PSM-dependent biofilm expansion was not observed, in accordance with our finding that no S. epidermidis PSM produced amyloids. In a mouse model of indwelling device-associated infection, the total psm deletion mutant had a significant defect in dissemination. Notably, the total psm mutant produced a significantly more substantial biofilm on the implanted catheter than the wild-type strain. Our study, which for the first time directly quantified the impact of PSMs on biofilm expansion on an implanted device, shows that the in vivo biofilm infection phenotype in S. epidermidis is in accordance with the PSM biofilm structuring and detachment model, which has important implications for the potential therapeutic application of quorum-sensing blockers.

A Derivative of Butyric Acid, the Fermentation Metabolite of Staphylococcus epidermidis, Inhibits the Growth of a Staphylococcus aureus Strain Isolated from Atopic Dermatitis Patients

The microbiome is a rich source of metabolites for the development of novel drugs. Butyric acid, for example, is a short-chain fatty acid fermentation metabolite of the skin probiotic bacterium Staphylococcus epidermidis (S. epidermidis). Glycerol fermentation of S. epidermidis resulted in the production of butyric acid and effectively hindered the growth of a Staphylococcus aureus (S. aureus) strain isolated from skin lesions of patients with atopic dermatitis (AD) in vitro and in vivo. This approach, however, is unlikely to be therapeutically useful since butyric acid is malodorous and requires a high concentration in the mM range for growth suppression of AD S. aureus. A derivative of butyric acid, BA–NH–NH–BA, was synthesized by conjugation of two butyric acids to both ends of an –NH–O–NH– linker. BA–NH–NH–BA significantly lowered the concentration of butyric acid required to inhibit the growth of AD S. aureus. Like butyric acid, BA–NH–NH–BA functioned as a histone deacetylase (HDAC) inhibitor by inducing the acetylation of Histone H3 lysine 9 (AcH3K9) in human keratinocytes. Furthermore, BA–NH–NH–BA ameliorated AD S. aureus-induced production of pro-inflammatory interleukin (IL)-6 and remarkably reduced the colonization of AD S. aureus in mouse skin. These results describe a novel derivative of a skin microbiome fermentation metabolite that exhibits anti-inflammatory and S. aureus bactericidal activity.

The small non-coding RNA RsaE influences extracellular matrix composition in Staphylococcus epidermidis biofilm communities

RsaE is a conserved small regulatory RNA (sRNA) which was previously reported to represent a riboregulator of central carbon flow and other metabolic pathways in Staphylococcus aureus and Bacillus subtilis. Here we show that RsaE contributes to extracellular (e)DNA release and biofilm-matrix switching towards polysaccharide intercellular adhesin (PIA) production in a hypervariable Staphylococcus epidermidis isolate. Transcriptome analysis through differential RNA sequencing (dRNA-seq) in combination with confocal laser scanning microscopy (CLSM) and reporter gene fusions demonstrate that S. epidermidis protein- and PIA-biofilm matrix producers differ with respect to RsaE and metabolic gene expression. RsaE is spatiotemporally expressed within S. epidermidis PIA-mediated biofilms, and its overexpression triggers a PIA biofilm phenotype as well as eDNA release in an S. epidermidis protein biofilm matrix-producing strain background. dRNA-seq and Northern blot analyses revealed RsaE to exist as a major full-length 100-nt transcript and a minor processed species lacking approximately 20 nucleotides at the 5'-end. RsaE processing results in expansion of the mRNA target spectrum. Thus, full-length RsaE interacts with S. epidermidis antiholin-encoding lrgA mRNA, facilitating bacterial lysis and eDNA release. Processed RsaE, however, interacts with the 5'-UTR of icaR and sucCD mRNAs, encoding the icaADBC biofilm operon repressor IcaR and succinyl-CoA synthetase of the tricarboxylic acid (TCA) cycle, respectively. RsaE augments PIA-mediated biofilm matrix production, most likely through activation of icaADBC operon expression via repression of icaR as well as by TCA cycle inhibition and re-programming of staphylococcal central carbon metabolism towards PIA precursor synthesis. Additionally, RsaE supports biofilm formation by mediating the release of eDNA as stabilizing biofilm matrix component. As RsaE itself is heterogeneously expressed within biofilms, we consider this sRNA to function as a factor favoring phenotypic heterogeneity and supporting division of labor in S. epidermidis biofilm communities.

Bacterial biofilms are highly organized structures which functionally emulate multicellular organisms, last but not least through heterogeneous gene expression patterns displayed by biofilm subpopulations. Here we analyzed the functions of the non-coding RNA RsaE in Staphylococcus epidermidis biofilm communities. RsaE exerted unexpected influences on S. epidermidis biofilm matrix composition by triggering localized eDNA release and facilitating PIA expression. RsaE accomplishes these effects by targeting mRNAs involved in bacterial lysis control, icaADBC expression and TCA cycle activity, with RsaE undergoing processing to exploit its full target potential. Interestingly, RsaE interaction with lysis-engaged lrgA mRNA is specific for S. epidermidis lrgA, but does not occur with lrgA mRNA from S. aureus, suggesting species-specific differences in staphylococcal lysis control. We speculate that RsaE-mediated bacterial lysis might represent a form of bacterial altruism contributing to biofilm structuring by providing nutrients to neighboring bacterial cells as well as by releasing eDNA as stabilizing biofilm matrix component. Due to its heterogeneous expression, we consider RsaE as a supporting factor that facilitates population diversity. Together, the data give insight into an unanticipated role of sRNAs as players in S. epidermidis biofilm organization.

Intraphagolysosomal conditions predispose to Staphylococcus epidermidis small colony variants persistence in macrophages

Staphylococcus epidermidis small colony variants can survive inside macrophages and their survival has been proposed as a pivotal process in the pathogenesis of biomaterial associated infections. In the present study the intracellular location of clinical isolates of SCV and parental wild type strains inside macrophages was determined. Furthermore, the effect of IFN-γ and rapamycin on the level of SCV/WT as well as lysosomes colocalisation and iNOS induction in THP-activated macrophages in response to WT and SCV strains of Staphylococcus epidermidis were examined. It was demonstrated that SCV strain of S. epidermidis can survive and persist inside macrophages and its intracellular survival is supported by the induction of phagosomal acidification. The ability to reduce the high proportion of LysoTracker positive SCV containing phagosomes was exclusively found when IFN-γ was used. The findings suggest that IFN-γ mediates SCV killing via two distinct mechanisms, phagosome alkalisation and an increased iNOS synthesis, so the cytokine may control S. epidermidis WT and SCV infection in macrophages. Staphylococcus epidermidis SCV is a less potent stimulus of iNOS than the WT strain and the feature may help SCV to persist in hostile environment of macrophages. Rapamycin treatment did not influence the iNOS synthesis but reduced the percentage of both bacterial strains within acidic organelles. However, the percentage of SCV within LysoTracker positive organelles, even though reduced comparing to non-primed cells, was higher than in the WT strain indicating that Staphylococcus epidermidis possesses unique metabolic features allowing SCV to survive within macrophages.

Staphylococcus epidermidis small basic protein (Sbp) forms amyloid fibrils, consistent with its function as a scaffolding protein in biofilms

Biofilms are communities of microbes embedded in a microbial extracellular matrix. Their formation is considered the main virulence mechanism enabling the opportunistic bacterial pathogen Staphylococcus epidermidis to cause devastating nosocomial, implant-associated infections. Biofilms often contain proteins, and an 18-kDa protein called small basic protein (Sbp) recently was discovered in the S. epidermidis biofilm matrix and may serve as a scaffolding protein in both polysaccharide intercellular adhesin (PIA)-dependent and accumulation-associated protein (Aap)-dependent biofilm formations. In Aap-mediated biofilm formation, Sbp colocalizes with Domain-B of Aap, implying that Sbp directly interacts with Aap's Domain-B. However, the structure of Sbp and its interaction with Aap, as well as the molecular mechanism underlying Sbp's roles in biofilm formation, are incompletely understood. In this work, we used small-angle X-ray scattering (SAXS), NMR, analytical size-exclusion chromatography, and isothermal titration calorimetry analyses to determine the Sbp structure and characterize its interaction with Aap's Domain-B. We found that Sbp is monomeric and partially folded in solution, and, unexpectedly, we observed no direct interactions between Sbp and Aap Domain-B. Instead, we noted that Sbp forms amyloid fibrils both in vitro and in vivo Atomic force, transmission electron, and confocal fluorescence microscopy methods confirmed the formation of Sbp amyloid fibrils and revealed their morphology. Taken together, the Sbp amyloid fibril structures identified here may account for Sbp's role as a scaffolding protein in the S. epidermidis biofilm matrix.

Spatiotemporal mapping of oxygen in a microbially-impacted packed bed using 19F Nuclear magnetic resonance oximetry

¹⁹F magnetic resonance has been used in the medical field for quantifying oxygenation in blood, tissues, and tumors. The ¹⁹F NMR oximetry technique exploits the affinity of molecular oxygen for liquid fluorocarbon phases, and the resulting linear dependence of ¹⁹F spin-lattice relaxation rate R₁ on local oxygen concentration. Bacterial biofilms, aggregates of bacteria encased in a self-secreted matrix of extracellular polymers, are important in environmental, industrial, and clinical settings and oxygen gradients represent a critical determinant of biofilm function. However, measurement of oxygen distribution in biofilms and biofouled porous media is difficult. Here the ability of ¹⁹F NMR oximetry to accurately track oxygen profile development in microbial impacted packed bed systems without impacting oxygen transport is demonstrated. Time-stable and inert fluorocarbon containing particles are designed which act as oxygen reporters in porous media systems. Particles are generated by emulsifying and entrapping perfluorooctylbromide (PFOB) into alginate gel, resulting in oxygen-sensing alginate beads that are then used as the solid matrix of the packed bed. ¹⁹F oxygenation maps, when combined with ¹H velocity maps, allow for insight into the interplay between fluid dynamics and oxygen transport phenomena in these complex biofouled systems. Spatial maps of oxygen consumption rate constants are calculated. The growth characteristics of two bacteria, a non-biofilm forming Escherichia coli and Staphylococcus epidermidis, a strong biofilm-former, are used to demonstrate the novel data provided by the method.

Monitoring metabolic reactions in Staphylococcus epidermidis exposed to silicon nitride using in situ time-lapse Raman spectroscopy

Staphylococcus epidermidis (S. epidermidis) is one of the leading nosocomial pathogens, particularly associated with periprosthetic infections of biomedical implants. Silicon nitride (Si3N4), a nonoxide biomaterial widely used in spinal implants, has shown bacteriostatic effects against both gram-positive and gram-negative bacteria; however, the physicochemical interactions between Si3N4 and bacteria yet remain conspicuously unexplored. In situ time-lapse Raman spectroscopic experiments were conducted by exposing S. epidermidis for 12, 24, and 48 h to Si3N4 substrates to understand the evolution of bacterial metabolism and to elucidate the ceramics antimicrobial behavior. The Raman probe captured an initial metabolic response of the bacteria to the adverse chemistry of the Si3N4 surface, which included peroxidation of membrane phospholipids and protein structural modifications to adjust for survivorship. However, beyond 24 h of exposure, the Raman signals representing DNA, lipids, proteins, and carbohydrates showed clear fingerprints of bacterial lysis. Bands related to biofilm formation completely disappeared or underwent drastically reduced intensity. Bacterial lysis was confirmed by conventional fluorescence microscopy methods. Spectroscopic experiments suggested that a pH change at the Si3N4's surface induced variations in the membrane structure and D-alanylation of teichoic acids in its peptidoglycan layer. Concurrent stimulation of peptidoglycan hydrolase (i.e., an enzyme involved with autolysis) ultimately led to membrane degradation and cellular death. An additional finding was that modulating the Si3N4 surface by increasing the population of amine groups improved the efficiency of the substrate against S. epidermidis, thus suggesting that optimization of the near-surface (alkaline) conditions may be a viable approach to bacterial reduction.

A Glance at the Role of Exotoxins in Opportunistic Bacterial Infections

The production and the mechanism of action of exotoxins from Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa are presented. The attack to the immune host's defenses is the main virulence factor of opportunistic bacteria in implant infections, favoring the invasion and colonization of compromised periprosthesis tissues.

Identification of Staphylococcal Quorum Sensing Inhibitors by Quantification of õ-Hemolysin with High Performance Liquid Chromatography

Quorum sensing plays a major role in regulation of virulence factor production by staphylococci. Chemical inhibitors that block this process and prevent the production of exotoxins and exoenzymes could have medical utility for infection prophylaxis and therapy. Here, we describe a high performance liquid chromatography method amenable to medium throughput screening for staphylococcal quorum sensing inhibitors by quantification of õ-hemolysin, a direct protein output of this system.

A Precision Microbiome Approach Using Sucrose for Selective Augmentation of Staphylococcus epidermidis Fermentation against Propionibacterium acnes

Acne dysbiosis happens when there is a microbial imbalance of the over-growth of Propionibacterium acnes (P. acnes) in the acne microbiome. In our previous study, we demonstrated that Staphylococcus epidermidis (S. epidermidis, a probiotic skin bacterium) can exploit glycerol fermentation to produce short-chain fatty acids (SCFAs) which have antimicrobial activities to suppress the growth of P. acnes. Unlike glycerol, sucrose is chosen here as a selective fermentation initiator (SFI) that can specifically intensify the fermentation activity of S. epidermidis, but not P. acnes. A co-culture of P. acnes and fermenting S. epidermidis in the presence of sucrose significantly led to a reduction in the growth of P. acnes. The reduction was abolished when P. acnes was co-cultured with non-fermenting S. epidermidis. Results from nuclear magnetic resonance (NMR) analysis revealed four SCFAs (acetic acid, butyric acid, lactic acid, and succinic acid) were detectable in the media of S. epidermidis sucrose fermentation. To validate the interference of S. epidermidis sucrose fermentation with P. acnes, mouse ears were injected with both P. acnes and S. epidermidis plus sucrose or phosphate buffered saline (PBS). The level of macrophage-inflammatory protein-2 (MIP-2) and the number of P. acnes in ears injected with two bacteria plus sucrose were considerably lower than those in ears injected with two bacteria plus PBS. Our results demonstrate a precision microbiome approach by using sucrose as a SFI for S. epidermidis, holding future potential as a novel modality to equilibrate dysbiotic acne.

Anti-biofilm potential of phenolic acids: the influence of environmental pH and intrinsic physico-chemical properties

Phenolic acids are a particular group of small phenolic compounds which have exhibited some anti-biofilm activity, although the link between their activity and their intrinsic pH is not clear. Therefore, the present work examined the anti-biofilm activity (inhibition of biomass and metabolic activity) of phenolic acids in relation to the environmental pH, as well as other physico-chemical properties. The results indicate that, while Escherichia coli was not inhibited by the phenolic acids, both methicillin resistant Staphylococcus aureus and methicillin resistant Staphylococcus epidermidis were susceptible to the action of all phenolic acids, with the pH playing a relevant role in the activity: a neutral pH favored MRSE inhibition, while acidic conditions favored MRSA inhibition. Some links between molecular polarity and size were associated only with their potential as metabolic inhibitors, with the overall interactions hinting at a membrane-based mechanism for MRSA and a cytoplasmic effect for MRSE.

Staphylococcus epidermidis adhesion on surface-treated open-cell Ti6Al4V foams

The effect of alkali and nitric acid surface treatments on the adhesion of Staphylococcus epidermidis to the surface of 60% porous open-cell Ti6Al4V foam was investigated. The resultant surface roughness of foam particles was determined from the ground flat surfaces of thin foam specimens. Alkali treatment formed a porous, rough Na2Ti5O11 surface layer on Ti6Al4V particles, while nitric acid treatment increased the number of undulations on foam flat and particle surfaces, leading to the development of finer surface topographical features. Both surface treatments increased the nanometric-scale surface roughness of particles and the number of bacteria adhering to the surface, while the adhesion was found to be significantly higher in alkali-treated foam sample. The significant increase in the number of bacterial attachment on the alkali-treated sample was attributed to the formation of a highly porous and nanorough Na2Ti5O11 surface layer.

Chemical Genetic Analysis and Functional Characterization of Staphylococcal Wall Teichoic Acid 2-Epimerases Reveals Unconventional Antibiotic Drug Targets

Here we describe a chemical biology strategy performed in Staphylococcus aureus and Staphylococcus epidermidis to identify MnaA, a 2-epimerase that we demonstrate interconverts UDP-GlcNAc and UDP-ManNAc to modulate substrate levels of TarO and TarA wall teichoic acid (WTA) biosynthesis enzymes. Genetic inactivation of mnaA results in complete loss of WTA and dramatic in vitro β-lactam hypersensitivity in methicillin-resistant S. aureus (MRSA) and S. epidermidis (MRSE). Likewise, the β-lactam antibiotic imipenem exhibits restored bactericidal activity against mnaA mutants in vitro and concomitant efficacy against 2-epimerase defective strains in a mouse thigh model of MRSA and MRSE infection. Interestingly, whereas MnaA serves as the sole 2-epimerase required for WTA biosynthesis in S. epidermidis, MnaA and Cap5P provide compensatory WTA functional roles in S. aureus. We also demonstrate that MnaA and other enzymes of WTA biosynthesis are required for biofilm formation in MRSA and MRSE. We further determine the 1.9Å crystal structure of S. aureus MnaA and identify critical residues for enzymatic dimerization, stability, and substrate binding. Finally, the natural product antibiotic tunicamycin is shown to physically bind MnaA and Cap5P and inhibit 2-epimerase activity, demonstrating that it inhibits a previously unanticipated step in WTA biosynthesis. In summary, MnaA serves as a new Staphylococcal antibiotic target with cognate inhibitors predicted to possess dual therapeutic benefit: as combination agents to restore β-lactam efficacy against MRSA and MRSE and as non-bioactive prophylactic agents to prevent Staphylococcal biofilm formation.

Staphylococcus aureus and Staphylococcus epidermidis cause life-threatening infections that are commonly acquired in hospitals as well as the community and remain difficult to treat with current antibiotics. In part, this is due to the emergence of methicillin-resistant S. aureus and S. epidermidis (MRSA and MRSE), which exhibit broad resistance to β-lactams such as penicillin and other members of this important founding class of antibiotics. Compounding this problem, Staphylococci commonly colonize the surface of catheters and other medical devices, forming bacterial communities that are intrinsically resistant to antibiotics. Here we functionally characterize a family of 2-epimerases, named MnaA and Cap5P, that we demonstrate by genetic, biochemical, and X-ray crystallography means are essential for wall teichoic acid biosynthesis and that upon their genetic inactivation render methicillin-resistant Staphylococci unable to form biofilms as well as broadly hypersusceptible to β-lactam antibiotics both in vitro and in a host infection setting. WTA 2-epimerases therefore constitute a novel class of methicillin-resistant Staphylococcal drug targets.

In vitro evaluation of microbial contamination of orthodontic brackets as received from the manufacturer using microbiological and molecular tests

OBJECTIVE

To test the null hypothesis that orthodontic brackets as supplied by manufacturers do not have microbial contamination.

MATERIALS AND METHODS

The sample comprised 140 brackets of four different commercially available brands, used directly from the manufacturer's packaging, divided into 14 groups (n  =  10 brackets each). Of the 140 pieces, 60 were full cases and 80 were replacement brackets. Materials were tested to detect bacterial growth, analyze types of bacteria present (biochemical test), and identify bacteria (molecular test with polymerase chain reaction [PCR]).

RESULTS

In two of 12 groups the brackets showed microbial contamination: group 1, Morelli full case brackets, and group 12, Abzil-3M Unitek replacement brackets. Staphylococcus aureus and Staphylococcus epidermidis were the bacteria identified in groups 1 and 12, respectively (suggested by the biochemical test and confirmed by PCR).

CONCLUSIONS

Brackets of two brands (Morelli and Abzil-3M Unitek) were found to be contaminated by bacteria in the original packages supplied by the manufacturers, which suggests a risk for patient contamination. These data suggest that the manufacturers of these materials should improve the quality control of the packaging used, including sterilization, for the security of patient health.

Effects of polysaccharide intercellular adhesin (PIA) in an ex vivo model of whole blood killing and in prosthetic joint infection (PJI): A role for C5a

BACKGROUND

A major complication of using medical devices is the development of biofilm-associated infection caused by Staphylococcus epidermidis where polysaccharide intercellular adhesin (PIA) is a major mechanism of biofilm accumulation. PIA affects innate and humoral immunity in isolated cells and animal models. Few studies have examined these effects in prosthetic joint infection (PJI).

METHODS

This study used ex vivo whole blood modelling in controls together with matched-serum and staphylococcal isolates from patients with PJI.

RESULTS

Whole blood killing of PIA positive S. epidermidis and its isogenic negative mutant was identical. Differences were unmasked in immunosuppressed whole blood pre-treated with dexamethasone where PIA positive bacteria showed a more resistant phenotype. PIA expression was identified in three unique patterns associated with bacteria and leukocytes, implicating a soluble form of PIA. Purified PIA reduced whole blood killing while increasing C5a levels. In clinically relevant staphylococcal isolates and serum samples from PJI patients; firstly complement C5a was increased 3-fold compared to controls; secondly, the C5a levels were significantly higher in serum from PJI patients whose isolates preferentially formed PIA-associated biofilms.

CONCLUSIONS

These data demonstrate for the first time that the biological effects of PIA are mediated through C5a in patients with PJI.

[Effects of inhibitory peptide of Staphylococcus epidermidis biofilm on adhesion and biofilm formation of this bacterium]

OBJECTIVE

To study the effects of inhibitory peptide of Staphylococcus epidermidis (SE) biofilm (briefly referred to as inhibitory peptide) on adhesion and biofilm formation of SE at early stage.

METHODS

By using peptide synthesizer, the inhibitory peptide was synthesized with purity of 96.8% and relative molecular mass of 874.4. (1) Solution of SE ATCC 35984 (the same below) was cultivated with inhibitory peptide in the final concentrations of 1-256 µg/mL, and the M-H broth without bacteria solution was used as blank control. The MIC of the inhibitory peptide against SE was determined (n=3). (2) Solution of SE was cultivated with trypticase soy broth (TSB) culture solution containing inhibitory peptide in the final concentrations of 16, 32, 64, 128, and 256 µg/mL (set as inhibitory peptide groups in corresponding concentration), and solution of SE being cultivated with TSB culture medium was used as negative control group. Growth of SE was observed every one hour from immediately after cultivation (denoted as absorbance value), and the growth curve of SE during the 24 hours of cultivation was drawn, with 3 samples in each group at each time point. (3) Solution of SE was cultivated with TSB culture solution containing inhibitory peptide in the final concentrations of 16, 32, 64, 128, and 256 µg/mL (set as inhibitory peptide groups in corresponding concentration), and solution of SE being cultivated with TSB culture medium was used as negative control group. Adhesive property of SE was observed after cultivation for 4 hours (denoted as absorbance value, n=10); biofilm formation of SE was observed after cultivation for 20 hours (denoted as absorbance value, n=10). (4) Solution of SE was cultivated with TSB culture solution containing inhibitory peptide in the final concentration of 128 µg/mL (set as 128 µg/mL inhibitory peptide group), and solution of SE being cultivated with TSB culture medium was used as negative control group. Adhesive property of SE and its biofilm formation were observed with confocal laser scanning microscope (CLSM), and the sample numbers were both 3. Data were processed with one-way analysis of variance, LSD test, and Dunnett T3 test.

RESULTS

(1) The MIC of inhibitory peptide against SE exceeded 256 µg/mL. (2) There was no significant difference in the growth curve of SE between inhibitory peptide groups in different concentrations and negative control group. (3) After 4 hours of cultivation, the absorbance values of adhesive property of SE in 256, 128, 64, and 32 µg/mL inhibitory peptide groups were respectively 0.20 ± 0.04, 0.27 ± 0.03, 0.35 ± 0.04, and 0.40 ± 0.04, which were significantly lower than the absorbance value in negative control group (0.53 ± 0.10, P<0.05 or P<0.01); the absorbance value of adhesive property of SE in 16 µg/mL inhibitory peptide group was 0.47 ± 0.09, which was close to the absorbance value in negative control group (P>0.05). After 20 hours of cultivation, the absorbance values of biofilm formation of SE in 256, 128, and 64 µg/mL inhibitory peptide groups were respectively 0.49 ± 0.10, 0.68 ± 0.06, and 0.93 ± 0.13, which were significantly less than the absorbance value in negative control group (1.21 ± 0.18, P<0.05 or P<0.01); the absorbance values of biofilm formation in 32 and 16 µg/mL inhibitory peptide groups were respectively 1.18 ± 0.22 and 1.15 ± 0.26, which were close to the absorbance value in negative control group (with P values above 0.05). (4) CLSM showed that more adhering bacteria and compact structure of biofilm were observed in negative control group, but less adhering bacteria and loose structure of biofilm were observed in 128 µg/mL inhibitory peptide group.

CONCLUSIONS

The inhibitory peptide can inhibit adhesion and biofilm formation of SE at early stage, but its structure still needs to be further modified.

Identification of axillary Staphylococcus sp. involved in the production of the malodorous thioalcohol 3-methyl-3-sufanylhexan-1-ol

The production of malodour by humans is mediated by bacterial transformation of naturally secreted, non-odorous molecules. Specifically in the underarm (axilla), malodour arises due to biotransformation by the microbiota of dipeptide-conjugated thioalcohols, particularly S-[1-(2-hydroxyethyl)-1-methylbutyl]-(L)-cysteinylglycine (Cys-Gly-3M3SH). This molecule, secreted by the axilla, has a well-established role in malodour when metabolized to free thioalcohol by bacteria. We present Cys-Gly-3M3SH biotransformation data from a library of skin-isolated corynebacteria and staphylococci and report a significant variation in thioalcohol generation across individual bacterial species. Staphylococcus hominis, Staphylococcus haemolyticus and Staphylococcus lugdunensis were particularly efficient Cys-Gly-3M3SH transformers. In contrast, Staphylococcus epidermidis and Corynebacterium tuberculostearicum, both highly prevalent axillary commensals, are low producers of 3M3SH. We also identify significant differences between the ability of several isolates to biotransform Cys-Gly-3M3SH compared to S-benzyl-L-Cys-Gly, a dipeptide-linked version of a commonly used malodour precursor substrate. Finally, using traditional biochemical assays we subsequently establish that Cys-Gly-3M3SH is actively transported into S. hominis, rather than passively diffusing across the membrane. This work significantly enhances our knowledge of Cys-Gly-3M3SH biotransformation by physiologically important bacteria in the axillary microbiota.

18 GHz electromagnetic field induces permeability of Gram-positive cocci

The effect of electromagnetic field (EMF) exposures at the microwave (MW) frequency of 18 GHz, on four cocci, Planococcus maritimus KMM 3738, Staphylococcus aureus CIP 65.8(T), S. aureus ATCC 25923 and S. epidermidis ATCC 14990(T), was investigated. We demonstrate that exposing the bacteria to an EMF induced permeability in the bacterial membranes of all strains studied, as confirmed directly by transmission electron microscopy (TEM), and indirectly via the propidium iodide assay and the uptake of silica nanospheres. The cells remained permeable for at least nine minutes after EMF exposure. It was shown that all strains internalized 23.5 nm nanospheres, whereas the internalization of the 46.3 nm nanospheres differed amongst the bacterial strains (S. epidermidis ATCC 14990(T) ~  0%; Staphylococcus aureus CIP 65.8(T) S. aureus ATCC 25923, ~40%; Planococcus maritimus KMM 3738, ~ 80%). Cell viability experiments indicated that up to 84% of the cells exposed to the EMF remained viable. The morphology of the bacterial cells was not altered, as inferred from the scanning electron micrographs, however traces of leaked cytosolic fluids from the EMF exposed cells could be detected. EMF-induced permeabilization may represent an innovative, alternative cell permeability technique for applications in biomedical engineering, cell drug delivery and gene therapy.

Identification of individual biofilm-forming bacterial cells using Raman tweezers

A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral “Raman fingerprints” obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

Formation of harmful compounds in biotransformation of lilial by microorganisms isolated from human skin

CONTEXT

The biotransformation of lilial results in an acid that is used in the dairy industry, in perfumery, as an intermediate in the manufacture of pharmaceuticals and cosmetics, and as a food additive for enhancing taste.

OBJECTIVE

This study investigates the biotransformation of lilial by Staphylococcus aureus and Staphylococcus epidermidis, two bacterial species isolated from human skin.

MATERIALS AND METHODS

Both species of Staphylococcus were isolated in samples taken from the skin of individuals living in a rural area of Iran. The pH of the culture medium was optimized, and after culturing the microorganisms, the bacteria were added to a flask containing a nutrient broth and incubated for several hours. The flasks of bacteria were combined with lilial, and various biochemical tests and diagnostics were performed, including Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectrophotometry (UV-Vis), and gas chromatography-mass spectroscopy (GC-MS).

RESULTS

The S. aureus produced isobutyric acid (2-methylpropanoic acid) after 72 h (71% of the total products yielded during biotransformation), whereas the S. epidermidis produced terpenoid alcoholic media after 24 h (90% of total products obtained).

DISCUSSION AND CONCLUSION

The results obtained indicate that biotransformation of lilial by S. aureus is more desirable than by S. epidermidis due to the highly efficient production of a single product. Bourgeonal and liliol were two toxic compounds produced during biotransformation, which indicates that the use of lilial in cosmetics can be harmful to the skin.

[Featuring pathogenicity factors in biofilm-forming and no-biofilm forming strains of Staphylococcus epidermidis]

A comparative study of the manifestation of pathogenicity factors: hemolytic, lipase, letsytinase activity and ability to adhere in 20 film-forming and 17 non-film-forming strains of S. epidermidis. Studying pathogenicity factors of the film-forming strains it was found that complete hemolysis and lipase activity shown was by all the film-forming strains of S. epidermidis, letsytinase activity was observed in 80%. Among the non-film-forming strains complete hemolysis and lipase activity were observed in 89% and letsytinase - 71%. Researched non-film-forming and film-forming strains of S. epidermidis showed the ability to adhere to buccal epithelial cells of humans. Found that all the film-forming strains of S. epidermidis were hight level adgesion, the highest IAM was equal to 11,84. It was found that among non-film-forming strains of S. epidermidis were low-, medium- and hight level adgesion. IAM of non-film-forming strains of S. epidermidis is 3 times lower compared to the IAM of the film-forming strains of human epithelial cells and was 3.2.

Effects of temperature on the morphological, polymeric, and mechanical properties of Staphylococcus epidermidis bacterial biofilms

Changes in temperature were found to affect the morphology, cell viability, and mechanical properties of Staphylococcus epidermidis bacterial biofilms. S. epidermidis biofilms are commonly associated with hospital-acquired medical device infections. We observed the effect of heat treatment on three physical properties of the biofilms: the bacterial cell morphology and viability, the polymeric properties of the extracellular polymeric substance (EPS), and the rheological properties of the bulk biofilm. After application of a 1 h heat treatment at 45 °C, cell reproduction had ceased, and at 60 °C, cell viability was significantly reduced. Size exclusion chromatography was used to fractionate the extracellular polymeric substance (EPS) based on size. Chemical analysis of each fraction showed that the relative concentrations of the polysaccharide, protein, and DNA components of the EPS were unchanged by the heat treatment at 45 and 60 °C. The results suggest that the EPS molecular constituents are not significantly degraded by the temperature treatment. However, some aggregation on the scale of 100 nm was found by dynamic light scattering at 60 °C. Finally, relative to control biofilms maintained at 37 °C, we observed an order of magnitude reduction in the biofilm yield stress after 60 °C temperature treatment. No such difference was found for treatment at 45 °C. From these results, we conclude that the yield stress of bacterial biofilms is temperature-sensitive and that this sensitivity is correlated with cell viability. The observed significant decrease in yield stress with temperature suggests a means to weaken the mechanical integrity of S. epidermidis biofilms with applications in areas such as the treatment of biofilm-infected medical devices.

Suppression of microbial metabolic pathways inhibits the generation of the human body odor component diacetyl by Staphylococcus spp

Diacetyl (2,3-butanedione) is a key contributor to unpleasant odors emanating from the axillae, feet, and head regions. To investigate the mechanism of diacetyl generation on human skin, resident skin bacteria were tested for the ability to produce diacetyl via metabolism of the main organic acids contained in human sweat. l-Lactate metabolism by Staphylococcus aureus and Staphylococcus epidermidis produced the highest amounts of diacetyl, as measured by high-performance liquid chromatography. Glycyrrhiza glabra root extract (GGR) and α-tocopheryl-l-ascorbate-2-O-phosphate diester potassium salt (EPC-K1), a phosphate diester of α-tocopherol and ascorbic acid, effectively inhibited diacetyl formation without bactericidal effects. Moreover, a metabolic flux analysis revealed that GGR and EPC-K1 suppressed diacetyl formation by inhibiting extracellular bacterial conversion of l-lactate to pyruvate or by altering intracellular metabolic flow into the citrate cycle, respectively, highlighting fundamentally distinct mechanisms by GGR and EPC-K1 to suppress diacetyl formation. These results provide new insight into diacetyl metabolism by human skin bacteria and identify a regulatory mechanism of diacetyl formation that can facilitate the development of effective deodorant agents.

Developing antifouling biointerfaces based on bioinspired zwitterionic dopamine through pH-modulated assembly

The use of synthetic biomaterials as implantable devices typically is accompanied by considerable nonspecific adsorption of proteins, cells, and bacteria. These may eventually induce adverse pathogenic problems in clinical practice, such as thrombosis and biomaterial-associated infection. Thus, an effective surface coating for medical devices has been pursued to repel nonspecific adsorption from surfaces. In this study, we employ an adhesive dopamine molecule conjugated with zwitterionic sulfobetaine moiety (SB-DA), developed based on natural mussels, as a surface ligand for the modification of TiO2. The electrochemical study shows that the SB-DA exhibits fully reversible reduction-oxidation behavior at pH 3, but it is irreversible at pH 8. A contact angle goniometer and X-ray photoelectron spectroscopy were utilized to explore the surface hydration, chemical states, and bonding mechanism of SB-DA. The results indicate that the binding between hydroxyl groups of SB-DA and TiO2 converts from hydrogen bonds to bidentate binding upon the pH transition from pH 3 to 8. In order to examine the antifouling properties of SB-DA thin films, the modified substrates were brought into contact with bovine serum albumin and bacteria solutions. The fouling levels were monitored using a quartz crystal microbalance with dissipation sensor and fluorescence optical microscope. Tests showed that the sample prepared via the pH transition approach provides the best resistance to nonspecific adsorption due to the high coverage and stability of the SB-DA films. These findings support the mechanism of the pH-modulated assembly of SB-DA molecules, and for the first time we demonstrate the antifouling properties of the SB-DA to be comparable with traditional thiol-based zwitterionic self-assemblies. The success of modification with SB-DA opens an avenue for developing a biologically inspired surface chemistry and can have applications over a wide spectrum of bioapplications. The strategy of the pH transition can also be applied to other functional dopamine derivatives.

Influence of poly-N-acetylglucosamine in the extracellular matrix on N-chlorotaurine mediated killing of Staphylococcus epidermidis

N-chlorotaurine (NCT) has recently been shown to have bactericidal activity against bacterial biofilm on metal discs (Coraca-Huber et al., 2014). In a biofilm, Staphylococcus epidermidis polymerizes poly-N-acetylglucosamine (PNAG) to form an extracellular matrix (ECM). Pseudomonas aeruginosa does not express this PNAG and has been shown to be highly susceptible to NCT. We compared the action of NCT on S. epidermidis 1457, a PNAG positive strain (SE1457) and S. epidermidis 1457- M10 an isogenic PNAG negative mutant (SE1457 M10). NCT-mediated killing was more effective and quicker on the PNAG negative strain SE1457 M10. Bacteria hidden in biofilms for prolonged periods of time were generally more susceptible than freshly formed biofilms. The differences in NCT-mediated killing might not be direct effects since NCT did not react with the monomeric N-acetylglucosamine, but might be explained by denser growth in the PNAG-containing biofilm produced by the wild type strain, which results in delayed penetration of NCT. The higher susceptibility of older biofilms to NCTmediated killing could be explained by more pronounced 3D architecture and subsequent larger surface area for interactions with NCT.

Identification of Staphylococcus epidermidis in the clinical microbiology laboratory by molecular methods

Biochemical assays for the phenotypic identification of coagulase-negative staphylococci in the clinical microbiology laboratory have been well described in previous publications (Becker and Von Eiff Manual of Clinical Microbiology, ASM Press, Washington, pp. 308-330, 2011; Kloos and Wolfshohl J Clin Microbiol 16:509-516, 1982). This discussion focuses on identification of Staphylococcus epidermidis through molecular and proteomic methods. Molecular assays have been shown to be more discriminatory between the coagulase-negative staphylococcal species than are phenotypic assays (Zadoks and Watts Vet Microbiol 134:20-28, 2009; Sheraba et al. BMC Res Notes 3:278, 2010; Patteet et al. Eur J Clin Microbiol Infect Dis 31:747-751, 2012). The molecular and proteomic methods that have shown the greatest utilization potential within the clinical laboratory are as follows: PCR amplification and sequencing of discriminatory genes, real-time polymerase chain reaction with species-specific probes in conjunction with a melt-curve analysis, fluorescence in situ hybridization, and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry.

The isolation and analysis of phenol-soluble modulins of Staphylococcus epidermidis

Phenol-soluble modulins (PSMs) are multifunctional peptide toxins produced by many staphylococcal strains. PSMs have received much recent attention, owing to multiple reports underscoring their importance for staphylococcal pathogenesis. Members of the PSM family may be strongly cytolytic to neutrophils and other cell types; promote inflammatory, receptor-mediated responses in several human cell types; and contribute to biofilm structuring and detachment. Here we describe biochemical methods to isolate, purify, and quantitatively analyze Staphylococcus epidermidis PSMs.

Rapid quantitative and qualitative analysis of biofilm production by Staphylococcus epidermidis under static growth conditions

Rapid screening of biofilm forming capacity by Staphylococcus epidermidis is possible using in vitro assays with 96-well plates. This method first developed by Christensen et al. in 1985 is fast and does not require specialized instruments. Thus, laboratories with standard microbiology infrastructure and a 96-well plate reader can easily use this technique to generate data on the biofilm phenotypes of multiple S. epidermidis strains and clinical isolates. Furthermore, this method can be adapted to gain insights into biofilm regulation and the characteristics of biofilms produced by different S. epidermidis isolates. Although this assay is extremely useful for showing whether individual strains are biofilm-positive or biofilm-negative and distinguishing between form weak, moderate or strong biofilm, it is important to acknowledge that the absolute levels of biofilm produced by an individual strain can vary significantly between experiments meaning that strict adherence to the protocol used is of paramount importance. Furthermore, measuring biofilm under static conditions does not generally reflect in vivo conditions in which bacteria are often subjected to shear stresses under flow conditions. Hence, the biofilm characteristics of some strains are dramatically different under flow and static conditions. Nevertheless, rapid measurement of biofilm production under static conditions is a useful tool in the analysis of the S. epidermidis biofilm phenotype.

Growth and preparation of Staphylococcus epidermidis for NMR metabolomic analysis

The "omics" era began with transcriptomics and this progressed into proteomics. While useful, these approaches provide only circumstantial information about carbon flow, metabolic status, redox poise, etc. To more directly address these metabolic concerns, researchers have turned to the emerging field of metabolomics. In our laboratories, we frequently use NMR metabolomics to acquire a snapshot of bacterial metabolomes during stressful or transition events. Irrespective of the "omics" method of choice, the experimental outcome depends on the proper cultivation and preparation of bacterial samples. In addition, the integration of these large datasets requires that these cultivation conditions be clearly defined.

Forces driving the attachment of Staphylococcus epidermidis to fibrinogen-coated surfaces

Cell surface proteins of bacteria play essential roles in mediating the attachment of pathogens to host tissues and, therefore, represent key targets for anti-adhesion therapy. In the opportunistic pathogen Staphylococcus epidermidis , the adhesion protein SdrG mediates attachment of bacteria to the blood plasma protein fibrinogen (Fg) through a binding mechanism that is not yet fully understood. We report the direct measurement of the forces driving the adhesion of S. epidermidis to Fg-coated substrates using single-cell force spectroscopy. We found that the S. epidermidis -Fg adhesion force is of ~150 pN magnitude and that the adhesion strength and adhesion probability strongly increase with the interaction time, suggesting that the adhesion process involves time-dependent conformational changes. Control experiments with mutant bacteria lacking SdrG and substrates coated with the Fg β(6-20) peptide, instead of the full Fg protein, demonstrate that these force signatures originate from the rupture of specific bonds between SdrG and its peptide ligand. Collectively, our results are consistent with a dynamic, multi-step ligand-binding mechanism called "dock, lock, and latch".

Penetration of erythromycin through Staphylococcus epidermidis biofilm

BACKGROUND

The catheter related infection caused by Staphylococcus epidermidis biofilm is increasing and difficult to treat by antimicrobial chemotherapy. The properties of biofilms that give rise to antibiotic resistance are only partially understood. This study aimed to elucidate the penetration of erythromycin through Staphylococcus epidermidis biofilm.

METHODS

The penetration ratio of erythromycin through Staphylococcus epidermidis biofilms of 1457, 1457-msrA, and wild isolate S68 was detected by biofilm penetration model at different time points according to the standard regression curve. The RNA/DNA ratio and the cell density within the biofilms were observed by confocal laser microscope and transmission electromicroscope, respectively.

RESULTS

The penetration ratios of erythromycin through the biofilms of 1457, 1457-msrA, and S68 after cultivation for 36 hours were 0.93, 0.55 and 0.4, respectively. The erythromycin penetration ratio through 1457 biofilm (0.58 after 8 hours) was higher than that through the other two (0.499 and 0.31 after 24 hours). Lower growth rate of the cells in biofilm was shown, with reduction of RNA/DNA proportion observed by confocal laser microscope through acridine orange stain. Compared with the control group observed by transmission electrmicroscope, the cell density of biofilm air face was lower than that of agar face, with more cell debris.

CONCLUSIONS

Erythromycin could penetrate to the Staphylococcus epidermidis biofilm, but could not kill the cells thoroughly. The lower growth rate of the cells within biofilm could help decreasing the erythromycin susceptibility.