RAPID, AUTOMATED SEPARATION OF SPECIFIC BACTERIA FROM LAKE WATER AND SEWAGE BY FLOW-CYTOMETRY AND CELL SORTING

The use of fluorescence-activated flow cytometric cell sorting to obta in highly enriched populations of viable target bacteria was investiga ted. Preliminary studies employed mixtures of Staphylococcus aureus an d Escherichia coli. Cells of S. aureus, when mixed in different propor tions with E. coli, could be selectively recovered at a purity in exce ss of 90%. This was possible even when S. aureus composed only approxi mately 0.4% of the total cells. Cell sorting was also tested for the a bility to recover E. coli from natural lake water populations and sewa ge. The environmental samples were challenged with fluorescently label led antibodies specific for E. coli prior to cell sorting. Final sampl e purities of greater than 70% were routinely achieved, as determined by CFU. Populations of E. coli released into environmental samples wer e recovered at greater than 90% purity. The use of flow cytometry and cell sorting to detect and recover viable target bacteria present at l evels of less than 1% within an indigenous microflora was also demonst rated.