Species Differences in the Clearance of Staphylococcus Aureus Bacteremia

Abstract

Studies on vascular graft infections may be influenced by species differences in bacteria clearance. The present study compares the bloodstream elimination of Staphylococcus aureus (S. aureus,) in dogs and pigs. Four mongrel dogs and four Yorkshire pigs received a 20-min infusion of 10⁶ S. aureus labeled with in-dium-131. Through a catheter placed in the infrarenal aorta, blood samples were removed at intervals for 5 h after infusion. The liver, spleen, and lungs were biopsied at 5 h. Blood and tissue samples were then counted in a gamma counter. The calculated phagocytotic index, k, for dogs was 8.6 × 10⁻⁴, while for pigs it was 1.5 × 10⁻³, indicating significantly faster bacterial clearance in pigs (p =. 009). After 2¹/₂ h, significantly fewer counts were present in pigs at most time points (p >. 05). Organ counts indicated higher counts in the dog liver and spleen and in the lungs of pigs (p >. 0001). This study indicates that S. aureus bacteremia is cleared faster by pigs, primarily by the lungs, compared to dogs, in which liver-spleen clearance predominated. These differences should be considered when the results of graft infection studies are compared.

Key Words:

• Bacterial clearance
• Vascular surgery
• laboratory animals
• swine
• dogs