Naser Abdallah Al Humam
Department of Microbiology, College of Veterinary Medicine, King Faisal University, Al-Ahsa, Saudi Arabia
ABSTRACT
Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are two bacterial pathogens responsible for different infectious diseases in the dromedary camel with different disease outcomes. In other species, different host-pathogen interaction mechanisms have been reported for E. coli and S. aureus. To investigate the modulatory effects of the two pathogen species on the camel innate immune system, the present study used plasma samples collected from E. coli and S. aureus blood cultures for stimulation of camel leukocytes in vitro. Using labeling of cell markers with monoclonal antibodies and flow cytometry, the changes in the expression of several cell markers on monocytes and neutrophilic granulocytes were identified. Plasma from either E. coli or S. aureus blood cultures resulted in a significant decrease in the expression level of CD14 on blood monocytes, the decrease was, however, significantly stronger for plasma from E. coli than S. aureus blood culture. In addition, only plasma from E. coli blood culture was able to reduce the expression of CD14 on stimulated granulocytes. This may represent an immune evasion mechanism of E. coli from the CD14-mediated innate recognition of gram-negative bacteria by camel monocytes and neutrophils. No changes were observed in the expression of CD163, MHCII or CD44 on neutrophils stimulated with plasma from either of the E. coli or S. aureus blood cultures. The different effects of plasma collected from E. coli stimulated blood and S. aureus stimulated blood on monocytes and neutrophils indicates a bacterial-species-specific modulating effect on camel monocytes and neutrophils.
Key words: Camel, bacterial blood culture, blood plasma, Escherichia coli, monocytes, neutrophils, Staphylococcus aureus