An immunochemical strategy based on peptidoglycan synthetic peptide epitopes to diagnose Staphylococcus aureus infections

• Antibodies towards a specific S. aureus peptidogycan epitope have been developed.
• The developed ELISA is able to detect S. aureus down to 104 CFU mL−1 in 2.5 h.
• Deglycosylation of the peptidoglycan increases the limit of detection of the assay.
• The assay is able to detect specifically S. aureus in respiratory samples.

The characteristic pentaglycyl cross-bridge of the Staphylococcus aureus peptidoglycan (PG) cell wall component is an attractive epitope to raise specific antibodies against this microorganism. Based on this approach, we report here for the first time a competitive ELISA able to detect S. aureus down to 104 CFU mL−1, without pre-enrichment on cell culture. The antibodies were raised against peptide-protein bioconjugates prepared by covalently coupling peptide haptens (PSau6 and PSau8) designed and synthesized taking into consideration the complex tridimensional structure in the PG polymer. Deglycosylation of the PG under acidic conditions has found to increase assay detectability. Assay performance has been evaluated in clinical samples such as bronchoalveolar lavage (BAL) and bronchoalveolar endotracheal aspirates (BAS) showing promising results for further implementation of this immunoassay as a daily routine diagnostic tool. Cross-reactivity studies have demonstrated that the immunoassay is specific for S. aureus.

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