Chemiluminescent analysis of Staphylococcus aureus utilizing phe11-protonectin against Gram-positive bacteria

Abstract A novel antimicrobial peptide named as phe 11 -protonectin was designed and synthesized by replacing the eleventh amino acid of protonectin with phenylalanine. Compared with broad-spectrum protonectin, this antimicrobial peptide showed greatly improved selectivity against Gram-positive bacteria. It was adopted to analyze Gram-positive bacteria utilizing its strong binding to cellular membrane. Using Staphylococcus aureus ( S. aureus ) as a model bacterium, a dual-site recognition-based chemiluminescent method was successfully established. Immunoglobulin G (IgG) was adopted as the capture agent for S. aureus , while alkaline phosphatase-conjugated phe 11 -protonectin was adopted as the tracer agent for S. aureus . Thus an enzyme-conjugated sandwich complex of S. aureus was formed, which allowed selective and sensitive analysis of this pathogen. Utilizing the dual-site recognition mechanism, the method showed a wide linear range of 1.0 × 10 3 - 1.0 × 10 7 CFU mL −1 and a low detection limit of 2.9 × 10 2 CFU mL -1 (3σ). The whole detection process can be accomplished within 130 min. It was successfully applied to analyze S. aureus in various sample matrixes including physiological saline injection, human urine and milk. The results demonstrated the application potential of the antimicrobial peptide in bacterial analysis.