Potential Use of Poly- N -Acetyl-β-(1,6)-Glucosamine as an Antigen for Diagnosis of Staphylococcal Orthopedic-Prosthesis-Related Infections

Abstract

Staphylococcus aureus and coagulase-negative staphylococci are microorganisms most frequently isolated from orthopedic-implant-associated infections. Their capacity to maintain these infections is thought to be related to their ability to form adherent biofilms. Poly-N-acetyl-␤-(1,6)-glucosamine (PNAG) is an important constituent of the extracellular biofilm matrix of staphylococci. In the present study, we explored the possibility of using PNAG as an antigen for detecting antibodies in the blood sera of patients with staphylococcal orthopedic-prosthesis-associated infections. First, we tested the presence of anti-PNAG antibodies in an animal model, in the blood sera of guinea pigs that developed an implant-associated infection caused by biofilm-forming, PNAG-producing strains of Staphylococcus epidermidis. Animals infected with S. epidermidis RP62A showed levels of anti-PNAG immunoglobulin G (IgG) significantly higher than those of the control group. The comparative study of healthy individuals and patients with staphylococcal prosthesis-related infections showed that (i) relatively high levels of anti-PNAG IgG were present in the blood sera of the healthy control group, (ii) the corresponding levels in the infected patients were slightly but not significantly higher, and (iii) only 1 of 10 patients had a level of anti-PNAG IgM significantly higher than that of the control group. In conclusion, the encouraging results obtained in the animal study could not be readily applied for the diagnosis of staphylococcal orthopedic-prosthesis-related infections in humans, and PNAG does not seem to be an appropriate antigen for this purpose. Further studies are necessary to determine whether the developed enzyme-linked immunosorbent assay method could serve as a complementary test in the individual follow-up treatment of such infections caused by PNAG-producing staphylococci.

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

“…High PIA antibody titers have been reported both in patients with SE biofilm prosthesis infections and in healthy controls (26,27). Due to the short incubation time in our experiments, any antibody-dependent complement activation relies on preexisting antibodies.…”

“…However, an association between level of anticoagulase-negative staphylococci antibodies and risk of neonatal coagulase-negative staphylococci sepsis has not been documented (32). PIA antibodies mainly belong to the IgG2 subclass (26,33), which are modest complement activators. Our study showed that there are significantly lower antibody titers both toward the biofilm matrix (PIA) and toward the whole bacterium (S. epidermidis SE1457) in cord blood of term infants as compared with adult blood.…”

“…The classical pathway can be activated through different mechanisms: (i) direct binding of bacterial surface components to the first classic factor, C1q, (ii) binding through C-reactive protein, or (iii) opsonization by antibodies bound to antigens on the bacterial surface, such as PIA (26) or other antigens in the biofilm/on the bacterial surface. High PIA antibody titers have been reported both in patients with SE biofilm prosthesis infections and in healthy controls (26,27).…”

“…The ELISA was performed as previously described (26). Briefly, Microlon 600 plates (Greiner-Bio, Frickenhausen, Germany) were coated with 100 µl highly purified PIA at 1 µg/ml in 40 mmol/l sodium phosphate buffer, incubated overnight at room temperature, and then washed.…”

Staphylococcal IgM Enzyme-Linked Immunosorbent Assay for Diagnosis of Periprosthetic Joint Infections

“…To date, attempts to design new serology diagnostic assays to diagnose bacterial biofilm infections of orthopedic implants early have failed (7,8). This study shows that high anti-SSPA IgM levels may provide for noninvasive detection of the immune response elicited by biofilm colonization on artificial orthopedic implants, improving patient monitoring with respect to infectious complications.…”