Determination of maximal bactericidal activity in human granulocytes

A conventional in vitro test assay was used to determine maximal bactericidal capabilities of human granulocytes. By means of a mathematical model the maximal phagocytosis and killing activity could be calculated for S. aureus and P. aeruginosa serving as test organisms. The evaluation allowed moreover the determination of the optimal bacterial load and also of critical bacterial concentrations leading to a complete depression of observable granulocyte killing functions. In contrast to other studies frozen suspensions of bacteria were used allowing the employment of identical microorganisms within a complete series of experiments. On average one granulocyte was found to ingest a maximum of 17 CFU of S. aureus with 9 CFU killed under optimal ratios of bacteria per granulocyte. For P. aeruginosa the granulocyte function reached peak values of 96 CFU ingested and 62 CFU killed per one granulocyte. The new assay might provide a highly reproducible method for clinical assessment of granulocyte dysfunctions in various diseases.