Application of flow cytometry to environmental control in marine aquaculture

The application of flow cytometry (FCM) technique for rapid detection of pathogenic bacteria for fish in marine aquaculture was described. To determine the number of viable bacteria cells, a fluorescein diacetate (FDA) was used. The difference in fluorescence scattergram between viable and dead cells was observed. The FCM method provided rapid determination of cell number of viable bacteria. A good correlation was observed between the values determined by the FCM method and the colony counting method in the range of 105–108 cells/ml. One FCM assay could be completed within 1 min. The FCM technique was also applied to rapid detection of pathogenic bacteria (Lactococcus garvieae). An antiserum against L. garvieae was prepared and its immunological property was examined. The detection of L. garvieae in cell suspensions contaminated with Escherichia coli was carried out. One FCM assay could be completed within 2 min and the total assay time including the preparation of bacterial sample was within 3 h.