Optical scatter patterns facilitate rapid differentiation of E nterobacteriaceae on CHROMagar TM O rientation medium

Summary E nterobacteriaceae family comprised pathogens and commensals and has a significant impact on food safety and public health. E nterobacteriaceae is often enumerated and presumptively identified on chromogenic media, such as CHROMagar TM O rientation medium based on colony profile; however, classification is highly arbitrary, and some could not be differentiated due to similar chromogen production. Here, we investigated the ability of the laser optical sensor, BARDOT (bacterial rapid detection using optical scattering technology) for rapid screening and differentiation of colonies of the major bacterial genera from E nterobacteriaceae on CHROMagar TM O rientation. A total of 36 strains representing 12 genera and 15 species were used to generate colony scatter image library that comprised 1683 scatter images. This library was used to differentiate mixed cultures of E nterobacteriaceae family – K lebsiella pneumoniae , E nterobacter spp., C itrobacter freundii and S erratia marcescens ( KECS group); P roteus mirabilis , M organella morganii and P rovidencia rettgeri ( PMP group); and non‐ E nterobacteriaceae family: P seudomonas aeruginosa , A cinetobacter spp. and S taphylococcus aureus ( PAS group) – and data show high accuracy (83–100%) for intra‐group classification of colonies in 10–22 h or even before visible production of chromogens. BARDOT successfully differentiated the major genera, including the ones that do not produce visually distinguishable chromogens on CHROMagar TM O rientation, providing a label‐free, real‐time on‐plate colony screening tool for E nterobacteriaceae .