Light‐scattering sensor for real‐time identification of V ibrio parahaemolyticus , V ibrio vulnificus and V ibrio cholerae colonies on solid agar plate

Summary The three most common pathogenic species of V ibrio , V ibrio cholerae , V ibrio parahaemolyticus and V ibrio vulnificus , are of major concerns due to increased incidence of water‐ and seafood‐related outbreaks and illness worldwide. Current methods are lengthy and require biochemical and molecular confirmation. A novel label‐free forward light‐scattering sensor was developed to detect and identify colonies of these three pathogens in real time in the presence of other vibrios in food or water samples. V ibrio colonies grown on agar plates were illuminated by a 635 nm laser beam and scatter‐image signatures were acquired using a CCD (charge‐coupled device) camera in an automated BARDOT ( BA cterial R apid D etection using O ptical light‐scattering T echnology) system. Although a limited number of V ibrio species was tested, each produced a unique light‐scattering signature that is consistent from colony to colony. Subsequently a pattern recognition system analysing the collected light‐scatter information provided classification in 1−2 min with an accuracy of 99%. The light‐scattering signatures were unaffected by subjecting the bacteria to physiological stressors: osmotic imbalance, acid, heat and recovery from a viable but non‐culturable state. Furthermore, employing a standard sample enrichment in alkaline peptone water for 6 h followed by plating on selective thiosulphate citrate bile salts sucrose agar at 30° C for ∼ 12 h, the light‐scattering sensor successfully detected V . cholerae , V . parahaemolyticus and V . vulnificus present in oyster or water samples in 18 h even in the presence of other vibrios or other bacteria, indicating the suitability of the sensor as a powerful screening tool for pathogens on agar plates.