Flow cytometric analysis of microorganisms

Abstract

This chapter discusses experimental approaches used to study individual microbial cells using flow cytometry and key factors that may impact these studies, including instrument setup, instrument operation, and sample preparation. It discusses the flow cytometric applications to the field of medical and food microbiology. Several approaches discussed include generic detection of microorganisms, specific identification of target organisms, cell viability determinations, and Gram staining. Experimental approaches to identifying microorganisms in liquid samples using flow cytometry include light scatter profiles, DNA content, immunoassays, neural nets, and rRNA probes, with varying degrees of success. Fluorescent dyes have been successfully used as indicators of cell viability in fluorescence microscopy and flow cytometry. Using these dyes, live and dead cells within a heterogeneous sample population can be identified and counted within a few minutes. Traditional methods employed to detect and enumerate bacteria (such as growth on laboratory media) require time (24 to 48 hr) and may underestimate the number of viable bacteria. Therefore, direct methods for the assessment of microbial viability are of increasing importance.