Application of bacteriophages for detection of foodborne pathogens

Abstract

Bacterial contamination of food products presents a challenge for the food industry and poses a high risk for the consumer. Despite increasing awareness and improved hygiene measures, foodborne pathogens remain a threat for public health, and novel methods for detection of these organisms are needed. Bacteriophages represent ideal tools for diagnostic assays because of their high target cell specificity, inherent signal-amplifying properties, easy and inexpensive production, and robustness. Every stage of the phage lytic multiplication cycle, from the initial recognition of the host cell to the final lysis event, may be harnessed in several ways for the purpose of bacterial detection. Besides intact phage particles, phage-derived affinity molecules such as cell wall binding domains and receptor binding proteins can serve for this purpose. This review provides an overview of existing phage-based technologies for detection of foodborne pathogens, and highlights the most recent developments in this field, with particular emphasis on phage-based biosensors.

Keywords: bacterial detection; biosensor; cell wall binding domain; diagnostics; foodborne pathogens; phage amplification; receptor binding protein; reporter phage.

Figure 1. Phage Amplification Assay using unmodified phage for detection of target cells (modified from ref. 9). 1) Target cells in a mixed bacterial culture are specifically recognized and infected by the phage; 2) extracellular phage particles are inactivated by addition of a virucide; 3) phage progeny liberated from target cells infect added helper cells, resulting in signal amplification; 4) countable plaques on an agar plate correspond to initial number of target cells in the sample.

Figure 2. Mixed culture of Listeria cells of different serovar groups labeled with differently-colored fluorescent reporter-CBD fusion proteins and visualized by fluorescence microscopy.

Figure 3. Composition of a bacteriophage-based biosensor for detection of bacterial pathogens (modified from ref. 12). The various recognition elements (phage, RBP, CBD) can be attached to the sensor surface by physical adsorption, covalent binding, or affinity tags.