ACCURATE FLOW CYTOMETRIC MEASUREMENT OF BACTERIA CONCENTRATIONS

Accurate measurements of bacteria concentrations are required in numer ous studies; they raise methodological problems that complicate, for i nstance, the investigations of polymorphonuclear neutrophil functions. We propose a new flow cytometric method of determining bacteria conce ntrations by comparison with a standardized fluorescent latex bead sol ution. Relative counts of beads and bacteria are established in a syst em using both fluorescence and light scatter for the two types of part icles. On the one hand, the latex bead size (0.98 mum in diameter) per mits counting on traditional hematological counters and, on the other, a flow cytometric detection with the same conditions for bacteria. Th e reproducibility of the study of bacteria concentration measurements gave a coefficient of variation of < 5 %.