Immobilized Reporter Phage on Electrospun Polymer Fibers for Improved Capture and Detection of <i>Escherichia coli</i> O157:H7

Abstract

Escherichia coli O157:H7 is a foodborne Shiga-toxin-producing bacterium that leads to millions of cases of illness every year. The development of a portable biosensor that rapidly detects this pathogen can greatly reduce both the time required to identify the source of contamination within the food production chain and the scale of outbreaks. Here we propose a swab for the detection of E. coli O157:H7 made from electrospun poly-3-hydroxybutyrate (PHB) on which the reporter bacteriophage (phage), PP01—engineered to express the bioluminescent protein Nanoluc upon infection of the pathogen—has been immobilized. In the development of the material, the properties of phage-immobilized electrospun porous, nonwoven PHB mats were compared to those of phage-immobilized flat PHB films produced by solvent casting. Dynamics of E. coli infections initiated with the phage-immobilized materials showed the electrospun mats had the highest infectivity, indicative of higher phage surface density (confirmed by microscopy) and activity—two important properties for the sensitivity and response time of biosensors. In sample tests, successful detection of E. coli O157:H7 cells in both milk and Tryptic Soy Broth at concentrations of 105 CFU/mL within 1 h and 101 CFU/mL within 3 h demonstrates the promising potential of the system as a food safety assessment tool.