Potential use of poly-N-acetyl-beta-(1,6)-glucosamine as an antigen for diagnosis of staphylococcal orthopedic-prosthesis-related infections

Staphylococcus epidermidis biofilm assembly and self-dispersion: bacteria and matrix dynamics

Staphylococcus epidermidis, despite being a commensal of human skin and mucosa, is a major nosocomial pathogen implicated in device-associated infections. The dissemination of infection to other body sites is related to biofilm dispersal. This study focused on the dispersion stage of S. epidermidis CIP 444 biofilm, with the assessment of biofilm matrix composition in a time-dependent experiment (7 days extended) with 3 independent repetitions, using confocal laser scanning microcopy (CLSM) in association with ZEN 3.4 blue edition, COMSTAT, and ImageJ software. SYTO-9, propidium iodide (PI), DID'OIL, FITC, and calcofluor white M2R (CFW) were used to stain biofilm components. The results indicated that the biomass of dead cells increased from 15.18 ± 1.81 µm3/µm2 (day 3) to 23.15 ± 6.075 µm3/µm2 (day 4), along with a decrease in alive cells' biomass from 22.75 ± 2.968 µm3/µm2 (day 3) to 18.95 ± 5.713 µm3/µm2 (day 4). When the intensities were measured after marking the biofilm components, in a 24-h-old biofilm, polysaccharide made up the majority of the investigated components (52%), followed by protein (18.9%). Lipids make up just 11.6% of the mature biofilm. Protein makes up the largest portion (48%) of a 4-day-old biofilm, followed by polysaccharides (37.8%) and lipids (7.27%). According to our findings, S. epidermidis CIP 444 dispersion occurred on day 4 of incubation, and new establishment of the biofilm occurred on day 7. Remarkable changes in biofilm composition will pave the way for a new approach to understanding bacterial strategies inside biofilms and finding solutions to their impacts in the medical field.

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.

Immunoreactive pattern of Staphylococcus epidermidis biofilm against human whole saliva

Saliva is essential to interact with microorganisms in the oral cavity. Therefore, the interest in saliva antimicrobial properties is on the rise. Here, we used an immunoproteomic approach, based on protein separation of Staphylococcus epidermidis biofilms by 2DE, followed by Western-blotting, to compare human serum and saliva reactivity profile. A total of 17 proteins were identified by MALDI-TOF/TOF. Serum and saliva presented a distinct pattern of immunoreactive proteins. Our results suggest that saliva seems to have higher propensity to react against S. epidermidis proteins with oxidoreductase activity and proteins involved with L-serine metabolic processes. We show that saliva was a powerful tool for the identification of potential S. epidermidis biofilms proteins.

Staphylococcus epidermidis biofilms induce lower complement activation in neonates as compared with adults

BACKGROUND

Staphylococcus epidermidis (SE) is an important cause of late-onset sepsis in neonates. SE frequently produces a polysaccharide intercellular adhesin (PIA) biofilm, important in the pathogenesis of these infections. Little is known about how the neonatal innate immune system reacts to SE biofilm-associated infections. Our hypothesis was that SE biofilms induce a lower complement activation in neonates as compared with adults.

METHODS

Cord blood from term infants (n = 15) and blood from adults (n = 6) were studied in an ex vivo whole-blood sepsis model. A PIA biofilm-producing strain (SE1457) and its isogenic mutant (M10), producing a non-PIA biofilm, were used.

RESULTS

Both SE biofilms induced stronger complement activation in adult than in cord blood (P ≤ 0.033). We found lower levels of antibodies toward both PIA (P = 0.002) and the whole bacterium (P = 0.001) in cord vs. adult blood. By contrast, the interleukin-8 (IL-8) and IL-6 secretion were higher in cord than in adult blood (P ≤ 0.002). The PIA biofilm induced stronger complement activation than the non-PIA biofilm.

CONCLUSION

We conclude that the neonatal complement system exhibits a maturational deficiency. This may reduce the ability of neonates to combat biofilm-associated SE infections.

A comparative study of antibodies against proteins extracted from staphylococcal biofilm for the diagnosis of orthopedic prosthesis-related infections in an animal model and in humans

Staphylococcus aureus and Staphylococcus epidermidis are the microorganisms most frequently seen in periprosthetic infections (PPI) with the capacity of forming biofilm. To find potential antigens for the diagnosis of PPI, the immunogenicity of protein components in biofilm from a model biofilm-positive strain (S. epidermidis RP62A) was investigated. A guinea pig animal model of PPI was developed and sera were obtained. Sera of patients with PPI and those of controls were also collected. Data generated with an enzyme-linked immunosorbent assay showed that there were significantly higher levels of anti-extracellular protein IgG in sera of infected animals than in controls. We also found significantly higher anti-extracellular protein IgG levels in infected patients, compared to the controls; however, receiver operating characteristic curves did not aid in diagnosing PPI.

Noninvasive Staphylococcus aureus biofilm determination in chronic rhinosinusitis by detecting the exopolysaccharide matrix component poly-N-acetylglucosamine

BACKGROUND

The role that bacterial biofilms might play in recalcitrant forms of chronic rhinosinusitis (CRS) is increasingly being recognized. However, the detection of bacteria existing in this form, using standard culture, is limited by their unique metabolically inactive properties. All current biofilm diagnostic modalities require invasive mucosal biopsies, which limit their use to the operating theatre.

METHODS

Twenty CRS patients and 5 controls were enrolled in a prospective study to assess the feasibility of noninvasively diagnosing S. aureus biofilms by detecting the biofilm matrix polysaccharide poly-N-acetylglucosamine (PNAG). An immunofluorescence protocol was developed for PNAG detection and compared with both standard microbiological cultures and fluorescence in situ hybridization (FISH).

RESULTS

Thirteen of 20 CRS patients had evidence of S. aureus biofilm formation using FISH. Of these, 12 had detectable PNAG. Interestingly none of the S. aureus FISH-negative patients were PNAG-positive despite the presence of coagulase-negative Staphylococci biofilms, some of which may exhibit PNAG in their pathogenic forms. The development of a noninvasive S. aureus biofilm diagnostic test provides a reliable means to identify a high-risk group of CRS patients who harbor S. aureus biofilms. The ability to be used outside of the perioperative period to assess surgical efficacy, guide management, and evaluate new treatment modalities provides a significant advance in this field of research and clinical practice.

CONCLUSION

This study has confirmed the feasibility of noninvasive detection of S. aureus biofilms with a simple test that produces results comparable to the more invasive methods that are currently relied upon.

Staphylococcus epidermidis polysaccharide intercellular adhesin activates complement

Staphylococcus epidermidis is a frequent cause of nosocomial infections. The central virulence factor of S. epidermidis is biofilm formation. Polysaccharide intercellular adhesin (PIA) constitutes the major biofilm matrix-component. PIA and biofilm have been implicated in S. epidermidis evasion of host immune defence. We examined the effects of S. epidermidis PIA on the inflammatory response with focus on complement activation. We used a human whole-blood ex vivo model of infection and compared the effects of a PIA-positive S. epidermidis strain (SE1457) and its PIA-negative isogenic mutant (M10). The independent effect of purified PIA on complement activation was investigated. In glucose-rich media, the mutant formed a proteinacious DNA-rich biofilm, whereas SE1457 formed a thick PIA-biofilm. In biofilm growth, SE1457 induced a stronger activation of the complement system compared with M10. We verified that purified PIA was independently responsible for a strong activation of the complement system. In contrast, M10 induced higher granulocyte activation by expression of CD11b and higher secretion of cytokines. We conclude that PIA has potent pro-inflammatory properties by activating the complement system. However, in a complex balance of the immune response, the decreased activation of granulocytes and cytokines by a PIA biofilm may limit host eradication of S. epidermidis.

Staphylococcal IgM enzyme-linked immunosorbent assay for diagnosis of periprosthetic joint infections

Delayed orthopedic joint prosthesis infections (DOJP-Is) due to staphylococci frequently result in prosthetic revision. Specific and noninvasive diagnostic tests are unavailable, and DOJP-Is are commonly diagnosed at advanced stages of disease. An enzyme-linked immunosorbent assay (ELISA) was developed to detect serum antibodies against staphylococcal slime polysaccharide antigens. Using a cutoff of 0.35 ELISA units, the test showed a specificity of 95.1% (95% confidence interval [CI], 85.4 to 98.7%) and a sensitivity of 89.7% (71.5 to 97.3%) on a sample of 90 individuals.

Structure, function and contribution of polysaccharide intercellular adhesin (PIA) to Staphylococcus epidermidis biofilm formation and pathogenesis of biomaterial-associated infections

Staphylococcus epidermidis is of major importance in infections associated with indwelling medical devices. The tight pathogenic association is essentially linked to the species ability to form adherent biofilms on artificial surfaces. Aiming at identifying novel targets for vaccination or therapy much effort has been made to unravel the molecular mechanisms leading to S. epidermidis biofilm formation. At present, polysaccharide intercellular adhesin (PIA) is the best studied factor involved in S. epidermidis biofilm accumulation. PIA is a glycan of beta-1,6-linked 2-acetamido-2-deoxy-D-glucopyranosyl residues of which 15 % are non-N-acetylated. PIA-producing S. epidermidis are widespread in clinical strain collections and PIA synthesis has been shown to be essential for S. epidermidis virulence. Moreover, PIA homologues have been identified in many other staphylococcal species, including the major human pathogen Staphylococcus aureus, and also Gram-negative human pathogens, suggesting that it might represent a more general pathogenicity principle in biofilm-related infections. In this review the current knowledge about the structure and biosynthesis of PIA is summarized. Additionally, information on its role in pathogenesis of biomaterial-related and other type of infections and the potential use of PIA and related compounds for prevention of infection is discussed.