Neuropathologic changes associated with systemic bacterial infection in 28 dogs.

Although systemic bacterial infection (SBI) is a common cause of sepsis and death in dogs, the neuropathology of canine SBI has been poorly characterized. Here we describe the neuropathologic features of SBI in a retrospective series of 28 dogs. The mean age of affected dogs was 5.5 y, and there was no sex or breed predisposition. Gross lesions in the brain were reported in 13 cases (46%) and consisted mainly of leptomeningeal hemorrhages in 10 of these cases (77%). Associated extraneural lesions included suppurative mitral valve endocarditis (12 cases; 43%) and pneumonia (10 cases; 36%). The main neurohistologic findings were neutrophilic (suppurative) and/or fibrinous meningoencephalitis with hemorrhage, vasculitis, thrombosis, and neuronal necrosis. Intralesional bacteria were observed in neutrophils or macrophages in 10 cases (77%). The putative primary site of infection was determined in 16 cases (57%) and consisted of pneumonia (6 cases; 38%), pyelonephritis (4 cases; 25%), and skin lesions (3 cases; 19%). Bacterial culture of fresh or frozen tissue samples yielded bacterial growth in 26 cases (93%), including Streptococcus canis (6 cases; 23%), Escherichia coli (4 cases; 15%), and Staphylococcus intermedius (3 cases; 12%).