ABSTRACT
UNLABELLED: Cronobacter is an emerging food pathogen, especially in infants and neonates, often associated with the ingestion of contaminated Powdered Infant Formula (PIF). Therefore, regulations require the control of the absence of Cronobacter and of Salmonella, another important food pathogen, in these food products. So far, reference and alternative methods take up to several days, and no validated method exists for the simultaneous detection of these two pathogens. In this work, we propose to address this issue by an innovative and easy-to-operate assay, named Plasmonic Immuno-Assay (PlasmIA), and by producing dedicated polyclonal antibodies. Our approach is based on Surface Plasmon Resonance imaging of antibody-arrays and bacterial growth during a standardized enrichment. Such a single-step assay enables the multiplex detection of both Cronobacter and Salmonella, with concentrations smaller than 30 CFU cells in 25 g PIF samples, in less than 1 day. SIGNIFICANCE AND IMPACT OF THE STUDY: Among bacterial pathogens involved in food contamination, Cronobacter and Salmonella are of particular interest. Nevertheless, all detection methods used so far require several days to assess food safety. In the present paper, we describe the first multiplex immuno-assay ever described for fast and specific detection of these two pathogens in food samples. Such advances were made possible by combining the advantages of protein microarrays with on-biochip culture of contaminated food samples and an easy-to-operate optical detection. By doing so, we managed to detect both viable Cronobacter and Salmonella occurring during the enrichment phase.
