Antimicrobial peptide-based array for Escherichia coli and Salmonella screening

Numerous bacteria, plants, and higher organisms produce antimicrobial peptides (AMPs) as part of their innate immune system, providing a chemical defense mechanism against microbial invasion. Many AMPs exert their antimicrobial activity by binding to components of the microbe's surface and disrupting the membrane. The goal of this study was to incorporate AMPs into screening assays for detection of pathogenic species. Surface-immobilized AMPs such as polymyxins B and E could be used to detect Salmonella typhimurium and Escherichia coli O157:H7 in two assay formats: direct and sandwich. Both types of assay confirmed that the peptides were immobilized in active form and could bind cells in a concentration-dependent manner. Cell binding to the AMPs was peptide-density dependent. This method for monitoring pathogen binding was extended to include other cationic AMPs such as cecropin A, magainin I and parasin. Detection limits (LODs) for E. coli O157:H7 and S. typhimurium obtained with AMPs during sandwich assays were in the ranges of 5 × 104 to 5 × 105 and 1 × 105 to 5 × 106 cells mL−1, respectively. The different AMPs showed significantly different affinities for the two bacterial species; the potential for classification of pathogens based on different binding patterns to AMPs is discussed.