Studies on phagocytosis in fish. I. In vitro uptake and killing of living Staphylococcus aureus by peripheral leucocytes of carp (Cyprinus carpio)

The clearance and uptake of Staphylococcus aureus were studied in vitro in whole blood of immunized and non immunized carp. Bacterial numbers were determined by: (1) counting viable cells in agar plates; (2) counting radioactivity of ¹⁴C labelled bacteria. Similar results were obtained by these two methods. Neither the bacterial growth nor the ingestion of bacteria into the cells seem to be influenced by immunization. In both immunized and non immunized groups the number of intracellular bacteria increased rapidly during the first 120 minutes, then progressed at a slow rate during the next 60 minutes, after which there was a rapid decrease in the number of bacteria only in the immune blood. It is concluded that the phagocytic cells of immune blood are more effective in activating or killing bacteria.