The effect of Staphylococcus aureus extraction factors on viability of neutrophils and monocytes in vitro

Staphylococcus aureus exoproteins are known to have potent effects on cells of the immune system in human infections and their primary inhibitory effects in vivo on innate immune responses. The objective of this study was to determine the effects of bacterial extractions on viability of neutrophils and monocytes in the healthy and the infected cattle (mastitis). In order to isolate of neutrophils and monocytes, heparinized blood samples were taken from the healthy (n=5) and the infected cattles (n=5). Neutrophil and monocyte isolation was carried out using meglumine and histopaque compounds respectively. Secretory factors from Staphylococcus aureus ATCC23219 were extracted and its concentration assayed by Bradford method and were determined to be 400 μg/ml. The effect of different concentrations of the extract on viability of neutrophils and monocytes was determined by flowcytometery and immunoflorcent respectively. The results showed that in the healthy and the infected cattles, extract containing 800 and 400 μg/ml protein, respectively caused the most death in monocytes and neutrophils. It also seemed that in the infected cattles, monocytes were more sensitive to cell death than the neutrophils. Discussion and The extract of Staphylococcus aureus induces apoptosis and necrosis in both neutrophils and monocytes of both the healthy and the infected cattle but the cells in the cattle with mastitis are more sensitive to apoptosis than in the non- infected cattles. In the case of mastitis due to Staphylococcus aureus, the bacterial extracts effects on monocytes and not the neutrophils. However, determination of bacterial extraction fractions and their effect on immune system cells are strongly recommended.