Phagocytosis in Staphylococcus aureus bacteriaemia in dogs

Staphylococcus aureus is the leading pathogenic cause of nosocomial infections, especially in bacteriaemia and sepsis. Phagocytosis is known to be an essential factor of innate immunity. The aim of this study was to evaluate phagocytic activity of leucocytes in experimental bacteriaemia. Bacteriaemia was induced in six adult male mongrel dogs (experimental group) by intravenous injection of Staphylococcus aureus isolate (1.2x109 cells/ml). Phagocytic activity was evaluated before infection (0 h.), and on the 2nd, 6th, 24th, 48th hour, and on the 7th, 14th and 21st day after infection. Six control animals were tested in the same dynamics. Phagocytic activity was evaluated by using the Nitrotetrazolium blue reduction (NBT) test, and the immune fluorescence method (Samnaliev et al., 1995) for detection of phagocytic index and percentage of phagocyting leucocytes (FITC marked Staphylococcus aureus were used). Percentage of phagocyting leucocytes showed an increase in experimental animals, compared to control animals, on the 24th h. Production of reactive oxygen species, evaluated by NBT, showed changes within experimental group as follows: an increase on the 24th h. compared to the 2nd h., 6th h., and the 14th day after infection; and an increase on 48th h., compared to the 2nd h. and 14th day. Comparison of reactive oxygen species production between groups, revealed an increase in the experimental group, as compared to the control group, on the 24th h. and on the 48th h. In conclusion cell elements of innate immunity are mostly activated on the first two days after inducing Staphylococcus aureus bacteriaemia in dogs