Flow Cytometry for Rapid Determination of Number of Microbial Cells Grown on Fish

Abstract

Application of the flow cytometry (FCM) technique for rapid determination of the total number of microbial cells grown on yellow-fin horse mackerel was described. An ultrasonic treatment was used to remove the cells on seafood samples of yellow-fin horse, Japanese common squid, short-neck, and common octopus. Almost of cells were removed from the samples in 9 min by the treatments. Since seafood products might contain various non-microbial debris particles in addition to microbial cells, propidium iodide was used to discriminate the two groups. A fluorescence histogram distinguished the cells from the particles. The FCM method allowed determination of the number of microbial cells adhering to fish during the preservation period. Cell numbers determined by FCM well paralleled that measured by the raditional colony counting method in the range of 105-109 cells/g. One FCM assay could be completed within 60 s and the total assay time including preparation of the microbial cells was within 30 min.