Host Response to Staphylococcus epidermidis Colonization and Infections

Computer-aided identification of lead compounds as Staphylococcal epidermidis FtsZ inhibitors using molecular docking, virtual screening, DFT analysis, and molecular dynamic simulation

In an effort to face the multiple drug-resistant bacteria, various approaches have been discovered to design potent compounds and search new targets through computational design tools. With an aim to identify selective inhibitors against filamentous temperature-sensitive mutant Z (FtsZ), a library of Phase database compounds have been virtually screened. High-throughput virtual screening of compounds against Staphylococcal epidermidis FtsZ protein (4M8I) was performed using three sequential docking modes like high-throughput virtual screening, Glide standard precision, followed by Glide extra precision. Four top-ranked compounds were selected from molecular mechanics-generalized Born surface area (MM-GBSA) binding energy with better predicted free binding energies of - 89.309, - 54.382, - 53.667, and - 52.133 kcal/mol, respectively. It is also showed that the contribution of van der Waals and electrostatic solvation energy terms are playing a major part to make the hit molecule (T6288784) binding to S. epidermidis FtsZ protein. The result of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and energy gap analysis predicts the molecular reactivity and stability of hit molecules. Subsequently, Lipinski's rule of five and properties of absorption, distribution, metabolism, and excretion (ADME) were to calculate their bioavailability. The average binding energy - 9.67 kcal/mol of the best proposed hit molecule (T6288784) was found with half-maximal inhibitory concentration (IC50) value to be 75.53 nM. A 15-ns molecular dynamics simulation study revealed the stable conformation of hit molecule. On a wide-range research discipline, in silico studies of our proposed compound confirm promising results and can be successfully used towards the development of novel FtsZ inhibitor with better binding affinity. Graphical Abstract.

Differential Expression of TFF1 and TFF3 in Patients Suffering from Chronic Rhinosinusitis with Nasal Polyposis

Trefoil family factor (TFF) proteins contribute to antimicrobial defense and the maintenance of sinonasal epithelial barrier integrity. Dysregulation of TFF expression may be involved in the development of chronic inflammation and tissue remodeling characteristically found in chronic rhinosinusitis with nasal polyposis (CRSwNP). Expressions of TFF1 and TFF3 were determined in specimens of middle nasal turbinate (MNT-0), bulla ethmoidalis (BE), and nasal polyps (NP) from CRSwNP patients (n = 29) and inferior nasal turbinate from a group of control patients (underwent nasal septoplasty, n = 25). An additional MNT sample was collected 6 months after functional endoscopic sinus surgery (FESS, MNT-6). TFF1 mRNA levels were significantly reduced in all specimens by approximately three- to five-fold, while TFF3 was increased in MNT-0, as compared with controls. Six months after surgery their levels were reversed to control values. CRSwNP patients with S. epidermidis isolated from sinus swabs showed upregulation of TFF3 in MNT and NP as compared with patients with sterile swabs. Target gene regulation was not affected by the presence of type 2 inflammation in patients with confirmed allergy. Results of this study imply participation of TFFs genes in the development of CRSwNP.

Staphylococcus aureus and the Cutaneous Microbiota Biofilms in the Pathogenesis of Atopic Dermatitis

Biofilm is the dominant mode of growth of the skin microbiota, which promotes adhesion and persistence in the cutaneous microenvironment, thus contributing to the epidermal barrier function and local immune modulation. In turn, the local immune microenvironment plays a part in shaping the skin microbiota composition. Atopic dermatitis (AD) is an immune disorder characterized by a marked dysbiosis, with a sharp decline of microbial diversity. During AD flares biofilm-growing Staphylococcus aureus emerges as the major colonizer in the skin lesions, in strict association with disease severity. The chronic production of inflammatory cytokines in the skin of AD individuals concurs at supporting S. aureus biofilm overgrowth at the expense of other microbial commensals, subverting the composition of the healthy skin microbiome. The close relationship between the host and microbial biofilm resident in the skin has profound implications on human health, making skin microbiota an attractive target for the therapeutic management of different skin disorders.

Back to Basics: Could the Preoperative Skin Antiseptic Agent Help Prevent Biofilm-Related Capsular Contracture?

BACKGROUND

Capsular contracture (CC) has remained an unresolved issue throughout history. Strong evidence focuses on bacterial biofilm as its main source. A literature review revealed that more than 90% of bacteria found in capsules and implants removed from patients with Baker grade III-IV CC belong to the resident skin microbiome (Staphylococcus epidermidis, predominant microorganism). The use of an adequate preoperative skin antiseptic may be a critical step to minimize implant contamination and help prevent biofilm-related CC.

OBJECTIVES

The authors sought to compare the effect of 2 different antiseptic skin preparations: povidone-iodine (PVP-I) vs chlorhexidine gluconate (CHG) on CC proportions after primary breast augmentation through a periareolar approach.

METHODS

In June of 2014, The Society for Healthcare Epidemiology of America proposed to use CHG for preoperative skin preparation in the absence of alcohol-containing antiseptic agents as strategy to prevent surgical site infection. The clinical safety committee of a surgical center in Colombia decided to change PVP-I to CHG for surgical site preparation thereafter. The medical records of 63 patients who underwent to primary breast augmentation through a periareolar approach during 2014 were reviewed. In the first 6 months PVP-I was used in 32 patients, and later CHG was employed in 31 patients.

RESULTS

Pearson's chi-squared test to compare CC proportions between subgroups showed a statistically significant difference. The CC proportion was higher for patients who had antisepsis with PVP-I. CC was absent when CHG was employed.

CONCLUSIONS

CHG as preoperative skin antiseptic for primary breast augmentation surgery was more effective than PVP-I to help prevent biofilm-related CC.

LEVEL OF EVIDENCE: 3

Association between biofilm formation, structure and antibiotic resistance in Staphylococcus epidermidis isolated from neonatal septicemia in southwest Iran

Background: Staphylococcus epidermidis has emerged as the pathogen from neonatal septicemia. Antibiotic resistance and the capability of biofilm formation make these infections much harder to treat. Hence, the aim of this study was to investigate the association between biofilm formation, structure and antibiotic resistance in S. epidermidis isolated from neonatal septicemia. Methods: Overall, 65 S. epidermidis isolates were recovered from blood cultures of neonatal septicemia. Antibiotic resistance pattern and the biofilm production were determined using phenotypic methods. The presence of ica operon, the bhp, the aap genes and SCCmec types were screened using PCR. Results: Most S.epidermidis isolates were resistant to erythromycin, while all isolates were sensitive to linezolid and vancomycin. Fifty-three percent of S.epidermidis isolates were resistant to methicillin. SCCmec types II was found commonly among methicillin-resistant S. epidermidis (MRSE) strains. The biofilm formation was observed in 65% of S.epidermidis isolates and the majority have polysaccharide matrix. icaA and icaD genes were found in 40% and 19% of isolates. Twenty-three isolates (62%) produced dissolvable polysaccharide intercellular adhesion (PIA)-dependent biofilms in SM after growth in TSB with NaCl and 14 (37%) isolates produced dissolvable protein-dependent biofilms in PK after growth in TSB with glucose. Three isolates (62%) produced dissolvable polysaccharide intercellular adhesion. Conclusion: Our data indicate the high rates of antibiotic resistance and the capability of biofilm formation among S. epidermidis isolates. Hence, the transmission of these strains can cause an increased risk of serious nosocomial infections.

An underestimated pathogen: Staphylococcus epidermidis induces pro-inflammatory responses in human alveolar epithelial cells

OBJECTIVES

Conventionally regarded as a harmless skin commensal, Staphylococcus epidermidis accounts for the majority of neonatal late-onset sepsis and is shown to be associated with neonatal inflammatory morbidities, especially bronchopulmonary dysplasia. This study addressed the pro-inflammatory capacity of different S. epidermidis strains on human alveolar epithelial cells.

METHODS

A549 cell monolayers were stimulated by live bacteria of S. epidermidis RP62A strain (biofilm-positive) and ATCC 12228 strain (biofilm-negative) at a multiplicity of infection ratio of 10 for 24 h. LPS (100 ng/ml) and Pam3CSK4 (1 µg/ml) were used for comparisons. Cell viability was measured by MTT method. The mRNA and protein expression of inflammatory mediators and toll-like receptor (TLR)-2 were assessed using RT-PCR, immunoassays and immunofluorescence.

RESULTS

Both S. epidermidis strains induced expression of tumor necrosis factor (TNF)-α, IL-1β, interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1, interferon γ-induced protein 10 (IP-10) and intercellular adhesion molecule (ICAM)-1, but not IL-10. The stimulatory effect of RP62A exceeded that of LPS (p < 0.05). RP62A strain showed a trend towards higher induction of pro-inflammatory mediators than ATCC 12228 strain. The co-stimulation with RP62A strain decreased cell viability compared to control and TLR agonists (p < 0.05). RP62A but not ATCC 12228 stimulated mRNA and protein expression of TLR2.

CONCLUSIONS

S. epidermidis drives pro-inflammatory responses in lung epithelial cells in vitro. The pro-inflammatory capacity of S. epidermidis may differ between strains. Biofilm-positive S. epidermidis strain seems to induce more potent pulmonary pro-inflammation than biofilm-negative S. epidermidis strain.

Evaluation of blood culture epidemiology and efficiency in a large European teaching hospital

Background

Blood cultures remain the gold standard for detecting bacteremia despite their limitations. The current practice of blood culture collection is still inefficient with low yields. Limited focus has been given to the association between timing of specimen collection at different time points during admission and their yield.

Methods

We carried out a retrospective observational study by analyzing all 3,890 sets of cultures collected from the 1,962 admitted patients over the seven-month period of this study. We compared the blood culture yield between the early group (≤24 hours after admission) and the late group (> 24 hours of admission). We also investigated the effect of prehospital oral antibiotics and pre-analytical time on the first cultures in the emergency department. Epidemiology and efficiency of blood cultures were studied for each medical specialty.

Results

In total, 3,349(86.1%) blood cultures were negative and 541(13.9%) were positive for one or more microorganisms. After correcting for contamination, the overall yield was 290 (7.5%). The early group (n = 1,490) yielded significantly more true-positive cultures (10.1% versus 5.8%, P<0.001) than the late group (n = 2,400). The emergency department had a significantly higher yield than general wards, 11.2% versus 5.7% (p<0.001). Prehospital oral antibiotic use and pre-analytical time did not affect the yield of first cultures at the emergency department (p = 0.735 and 0.816 respectively). The number of tests needed to obtain one true-positive culture varied between departments, ranging from 7 to 45.

Conclusion

This study showed that blood cultures are inefficient in detecting bacteremia. Cultures collected during 24 hours after admission yielded more positive results than those collected later. Significant variations in blood culture epidemiology and efficiency per specialty suggest that guidelines should be reevaluated. Future studies should aim at improving blood culture yield, implementing educational programs to reduce contamination and cost-effective application of modern molecular diagnostic technologies.

[The inhibition of accessory gene regulator C specific binding peptides on biofilm formation of Staphylococcus epidermidis on the surface of polyvinyl chloride in vitro]

Objective

To investigate the effect of accessory gene regulator C (agr C) specific binding peptides (named N1) on the biofilm formation of Staphylococcus epidermidis on the surface of polyvinyl chloride (PVC) materials in vitro.

Methods

Firstly, the two strains (ATCC35984, ATCC12228) were cultured with N1 at concentrations of 100, 200, 400, 800, and 1 600 μg/mL, respectively. The control group was cultured with agrC specific binding unrelated peptides (named N0) at the same concentrations and the absorbance ( A) value was measured after 24 hours to determine the optimal bacteriostatic concentration of N1. The two strains were cultured with N1 and N0 of the optimal concentration, respectively. The A values were measured at 6, 12, 18, 24, 30, and 48 hours to observe the effect of N1 on the biofilm formation ability of Staphylococcus epidermidis. On this basis, the surface structure of the biofilm on the surface of PVC material was observed by scanning electron microscopy after 6, 12, 18, 24, and 30 hours of incubation with PVC material sheet. The thickness of the biofilm was observed by laser confocal microscopy after 6, 12, 18, and 24 hours of incubation with ATCC35984 strain.

Results

The optimal bacteriostatic concentration of N1 was 800 μg/mL. ATCC 12228 strain did not form obvious biofilm after being cultured with N1 and N0. When ATCC35984 strain was cultured with N1 and N0 for 12 hours, the difference in biofilm formation ability between groups N1 and N0 was statistically significant ( P<0.05), but there was no significant difference at 6, 18, 24, 30, and 48 hours ( P>0.05). Scanning electron microscopy examination showed that mature biofilm structure was observed in ATCC35984 strain and was not observed in ATCC12228 strain. Laser confocal microscopy observation showed that the number of bacteria in the group N1 was significantly lower than that in the group N0 at 12 hours, and the most of bacteria were dead bacteria. There was no significant difference in the number of bacteria at 6, 18, and 24 hours, and the most of them were live bacteria. The biofilm thickness of group N1 was significantly lower than that of group N0 at 12 and 18 hours ( P<0.05).

Conclusion

The intensity of N1 inhibiting the formation of Staphylococcus epidermidis biofilm is dose-dependent. During the aggregation period, N1 can inhibit the biofilm formation by hindering the bacterial growth and aggregation. The inhibition effect on mature biofilm is not obvious.

Differential involvement of glycans in the binding of Staphylococcus epidermidis and Corynebacterium spp. to human sweat

Sweat is a secretory fluid that can be a source of unpleasant body odour due to interaction of resident bacteria with sweat components. Identification of glycoproteins in sweat suggests that protein-conjugated glycans may act as binding epitopes for bacteria, as found in other secretory fluids such as human milk, tears and saliva which help to protect epithelial surfaces from infection. We conducted proteomic and glycomic analysis of sweat to reveal an abundance of glycoproteins, predominantly carrying bi-antennary sialylated N-glycans with or without fucose. A fluorescent plate assay was used to determine whether glycans on sweat proteins provide binding epitopes for odour-producing skin commensals Staphylococcus epidermidis and Corynebacterium. Sialic acid and fucose were found to be important binding epitopes for S. epidermidis 3-22-BD-6, a strain recently isolated from human sweat, whereas fucose (but not sialic acid) contributed to the binding of Type strain S. epidermidis ATCC 12228. In contrast, our results indicate that sweat N-glycans do not provide binding epitopes for Corynebacterium. Synthetic sugar mimics of Lewis blood group antigens were investigated as potential inhibitors of the binding of S. epidermidis 3-22-BD-6 to sweat. Pre-incubation of the bacterium with LeB, LeX, LeY and sLeX (pentaose) resulted in a significant reduction in sweat protein adhesion indicating that terminal fucose is a key binding epitope, particularly when linked to a Type 2 chain (Galβ1-4GlcNAc) configuration (LeY). Our results form an impetus for future studies seeking to elucidate the role of glycans in sweat associated malodour, with possible implications for cosmetic and medical fields.

Interactions between Host Immunity and Skin-Colonizing Staphylococci: No Two Siblings Are Alike

As the outermost layer of the body, the skin harbors innumerable and varied microorganisms. These microorganisms interact with the host, and these interactions contribute to host immunity. One of the most abundant genera of skin commensals is Staphylococcus. Bacteria belonging to this genus are some of the most influential commensals that reside on the skin. For example, colonization by Staphylococcus aureus, a well-known pathogen, increases inflammatory responses within the skin. Conversely, colonization by Staphylococcus epidermis, a coagulase-negative staphylococcal species that are prevalent throughout the skin, can be innocuous or beneficial. Thus, manipulating the abundance of these two bacterial species likely alters the skin microbiome and modulates the cutaneous immune response, with potential implications for various inflammation-associated skin diseases. Importantly, before researchers can begin manipulating the skin microbiome to prevent and treat disease, they must first fully understand how these two species can modulate the cutaneous immune response. In this review, we discuss the nature of the interactions between these two bacterial species and immune cells within the skin, discussing their immunogenicity within the context of skin disorders.

Disease-associated genotypes of the commensal skin bacterium Staphylococcus epidermidis

Some of the most common infectious diseases are caused by bacteria that naturally colonise humans asymptomatically. Combating these opportunistic pathogens requires an understanding of the traits that differentiate infecting strains from harmless relatives. Staphylococcus epidermidis is carried asymptomatically on the skin and mucous membranes of virtually all humans but is a major cause of nosocomial infection associated with invasive procedures. Here we address the underlying evolutionary mechanisms of opportunistic pathogenicity by combining pangenome-wide association studies and laboratory microbiology to compare S. epidermidis from bloodstream and wound infections and asymptomatic carriage. We identify 61 genes containing infection-associated genetic elements (k-mers) that correlate with in vitro variation in known pathogenicity traits (biofilm formation, cell toxicity, interleukin-8 production, methicillin resistance). Horizontal gene transfer spreads these elements, allowing divergent clones to cause infection. Finally, Random Forest model prediction of disease status (carriage vs. infection) identifies pathogenicity elements in 415 S. epidermidis isolates with 80% accuracy, demonstrating the potential for identifying risk genotypes pre-operatively.

Coagulase-Negative Staphylococcus Skin and Soft Tissue Infections

Coagulase-negative staphylococcus organisms may be normal flora of human skin, however these bacteria can also be pathogens in skin and soft tissue infections. A summary of skin and soft tissue infections caused by coagulase-negative staphylococcus species is provided in this review. We conducted a search of the PubMed database using the following terms: abscess, auricularis, biofilm, capitis, cellulitis, coagulase, contaminant, cyst, draining, epidermidis, felon, folliculitis, furuncle, haemolyticus, hominis, indolent, infection, lugdunensis, mecA, microbiome, negative, osteomyelitis, paronychia, saprophyticus, skin, simulans, sinus, soft, staphylococcus, systemic, tissue, virulence, virulent, and vulvar. The relevant papers, and their references, generated by the search were reviewed. Skin and soft tissue infections have been observed to be caused by many coagulase-negative staphylococcus organisms: Staphylococcus auricularis, Staphylococcus capitis, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus lugdunensis, Staphylococcus saprophyticus, and Staphylococcus simulans. Coagulase-negative staphylococcus skin infections predominantly present as abscesses and paronychia. They are most common in elderly patients or those individuals who are immunosuppressed, and tend to be broadly susceptible to antibiotic treatment. In conclusion, albeit less common, coagulase-negative staphylococcus organisms can result in skin and soft tissue infections, particularly in older and/or immunocompromised individuals. A review of the literature found that coagulase-negative staphylococcus organisms are most commonly grown in cultures of abscesses and paronychia. Therefore, coagulase-negative staphylococcal organisms should not always be considered as contaminants or normal flora, but rather as causative pathogens. They are usually susceptible to antibiotics used to treat methicillin-sensitive Staphylococcus aureus.

Beyond sepsis: Staphylococcus epidermidis is an underestimated but significant contributor to neonatal morbidity

Staphylococcus epidermidis accounts for the majority of cases of neonatal sepsis. Moreover, it has been demonstrated to be associated with neonatal morbidities, such as bronchopulmonary dysplasia (BPD), white matter injury (WMI), necrotizing enterocolitis (NEC) and retinopathy of prematurity (ROP), which affect short-term and long-term neonatal outcome. Imbalanced inflammation has been considered to be a major underlying mechanism of each entity. Conventionally regarded as a harmless commensal on human skin, S. epidermidis has received less attention than its more virulent relative Staphylococcus aureus. Particularities of neonatal innate immunity and nosocomial environmental factors, however, may contribute to the emergence of S. epidermidis as a significant nosocomial pathogen. Neonatal host response to S. epidermidis sepsis has not been fully elucidated. Evidence is emerging regarding the implication of S. epidermidis sepsis in the pathogenesis of neonatal inflammatory diseases. This review focuses on the interplay among S. epidermidis, neonatal innate immunity and inflammation-driven organ injury.

Induced surface proteins of Staphylococcus [corrected] epidermidis adhering to titanium implant substrata

OBJECTIVE

Staphylococcus epidermidis, as a primary colonizer, is strongly associated with infections of (dental) implants (i.e., peri-implantitis), but little is known about the surface proteome of this bacterium. For the identification of bacterial adhesins, this study investigated the surface proteome of S. epidermidis adhering directly to titanium implant substrata.

MATERIALS AND METHODS

S. epidermidis strain ATTC 35984 was cultured either planktonically or on titanium implant specimens. The surface proteomes were isolated by mutanolysin digestion, and proteins were separated by 2D gel electrophoreses to reveal highly expressed proteins only. Protein spots were visualized by silver staining and proteins were identified by mass spectrometry.

RESULTS

Surface proteome analyses of S. epidermidis on titanium identified six expressed proteins. Three proteins were highly expressed on the titanium implants including accumulation-associated protein Q8CQD9. These specific proteins could be potential pathogenicity factors of bacteria in peri-implant biofilms.

CONCLUSION

For the first time, our study identified S. epidermidis surface proteins, which are expressed after adhesion to titanium implant materials.

CLINICAL RELEVANCE

Our study reveals possible candidates for a newly protein-based vaccine against peri-implantitis.

Immune Evasion Mechanisms of Staphylococcus epidermidis Biofilm Infection

The primary virulence factor of the skin commensal and opportunistic pathogen, Staphylococcus epidermidis, is the ability to form biofilms on surfaces of implanted materials. Much of this microorganism’s pathogenic success has been attributed to its ability to evade the innate immune system. The primary defense against S. epidermidis biofilm infection consists of complement activation, recruitment and subsequent killing of the pathogen by effector cells. Among pathogen-derived factors, the biofilm exopolysaccharide polysaccharide intercellular adhesion (PIA), as well as the accumulation-associated protein (Aap), and the extracellular matrix binding protein (Embp) have been shown to modulate effector cell-mediated killing of S. epidermidis. Phenol-soluble modulins (PSMs) constitute the only class of secreted toxins by S. epidermidis, at least one type of which (PSMδ) possesses strong cytolytic properties toward leukocytes. However, through selective production of non-cytolytic subtypes of PSMs, S. epidermidis is able to maintain a low inflammatory infection profile and avoid eradication by the host immune system. Taken together, our emerging understanding of the mechanisms behind immune modulation by S. epidermidis elucidates the microorganism’s success in the initial colonization of device surfaces as well as the maintenance of a chronic and indolent course of biofilm infection.

Pathogenic Mechanisms and Host Interactions in Staphylococcus epidermidis Device-Related Infection

Staphylococcus epidermidis is a permanent member of the normal human microbiota, commonly found on skin and mucous membranes. By adhering to tissue surface moieties of the host via specific adhesins, S. epidermidis is capable of establishing a lifelong commensal relationship with humans that begins early in life. In its role as a commensal organism, S. epidermidis is thought to provide benefits to human host, including out-competing more virulent pathogens. However, largely due to its capacity to form biofilm on implanted foreign bodies, S. epidermidis has emerged as an important opportunistic pathogen in patients receiving medical devices. S. epidermidis causes approximately 20% of all orthopedic device-related infections (ODRIs), increasing up to 50% in late-developing infections. Despite this prevalence, it remains underrepresented in the scientific literature, in particular lagging behind the study of the S. aureus. This review aims to provide an overview of the interactions of S. epidermidis with the human host, both as a commensal and as a pathogen. The mechanisms retained by S. epidermidis that enable colonization of human skin as well as invasive infection, will be described, with a particular focus upon biofilm formation. The host immune responses to these infections are also described, including how S. epidermidis seems to trigger low levels of pro-inflammatory cytokines and high levels of interleukin-10, which may contribute to the sub-acute and persistent nature often associated with these infections. The adaptive immune response to S. epidermidis remains poorly described, and represents an area which may provide significant new discoveries in the coming years.