Simultaneous flow cytometric measurement of Streptococcus suis phagocytosis by polymorphonuclear and mononuclear blood leukocytes.

A simple flow cytometric method was used to study simultaneously the phagocytosis of Streptococcus suis serotype 2 by polymorphonuclear and mononuclear blood leukocytes from swine and humans. Using this method with a bacteria-to-leukocytes ratio of 10:1 and after 60 min of incubation, 80.2 +/- 2.8% of swine granulocytes and 77.0 +/- 2.8% of swine monocytes were shown to contain FITC-labelled S. suis serotype 2 strain 735. Using the same strain, FITC-labelled bacteria were found in 95.5 +/- 3.2% of human granulocytes and in 92.8 +/- 3.6% of human monocytes. The phagocytosis rates of avirulent and virulent strains of S. suis were not significantly different.