ABSTRACT
Since its development in the 1970s as a commercially available technology for cell analysis, flow cytometry (FC) has held significant potential as a tool for microbiologists. In the intervening 20 years, however, analysis of bacteria has lagged far behind the advances made in the analysis of eukaryotic cells by immunologists and cell biologists: of over 23,000 Medline references to FC, only 571 also referenced bacteria. There are two major reasons for this discrepancy. The optical configurations of most commercially available flow cytometers are optimized for analysis of intact cells in the size range of eukaryotic cells, especially lymphocytes, rather than for analysis of small cells such as bacteria. Second, there is a lack of well-characterized, specific molecular probes for bacterial analysis; the almost universal use of FC in immunology is driven by the availability of fluorochrome-labeled probes for specific molecules. Our laboratory became involved in analysis of bacteria by FC as a result of developing methods to measure uptake and survival of facultative intracellular bacteria by phagocytic cells (Raybourne and Bun-
ning, 1994). As part of these studies, it was necessary to analyze fluorochrome-labeled bacteria by FC. This led to firsthand experience with the above problems and an interest in investigating the practicality of FC as a method for detection and isolation of pathogenic bacteria in an applied setting such as food microbiology.
