Brain microabscesses in a porcine model of Staphylococcus aureus sepsis

Abstract

Background: Sepsis caused by Staphylococcus aureus often leads to brain microabscesses in humans. Animal models of haematogenous brain abscesses would be useful to study this condition in detail. Recently, we developed a model of S. aureus sepsis in pigs and here we report that brain microabscesses develop in pigs with such induced S. aureus sepsis.Twelve pigs were divided into three groups. Nine pigs received an intravenous inoculation of S. aureus once at time 0 h (group 1) or twice at time 0 h and 12 h (groups 2 and 3). In each group the fourth pig served as control. The pigs were euthanized at time 12 h (Group 1), 24 h (Group 2) and 48 h (Group 3) after the first inoculation. The brains were collected and examined histopathologically.

Results: All inoculated pigs developed sepsis and seven out of nine pigs developed brain microabscesses. The microabscesses contained S. aureus and were located in the prosencephalon and mesencephalon. Chorioditis and meningitis occurred from 12 h after inoculation.

Conclusions: Pigs with experimental S. aureus sepsis often develop brain microabscesses. The porcine brain pathology mirrors the findings in human sepsis patients. We therefore suggest the pig as a useful animal model of the development of brain microabscesses caused by S. aureus sepsis.

Figure 1

Focal brain microabscess. The abscess consists of a necrotic centre surrounded by a rim of neutrophils and edema. Pig No. 2. Haematoxylin and eosin. Bar = 100 μm.

Figure 2

Focal brain microabscess with Staphylococcus aureus. This staining shows presence of S. aureus antigen in the centre of a microabscess. Pig No. 2; same abscess as in Figure 1. Immunohistochemical staining for S. aureus antigen. Bar = 100 μm.

Figure 3

Suppurative choroiditis. Infiltration with neutrophils in the stroma of the choroid villi. Pig No. 5. Haematoxylin and eosin. Bar = 50 μm.