The Pathogenesis of Staphylococcus aureus Infection in the Diabetic NOD Mouse

Abstract

Although Staphylococcus aureus is a major pathogen implicated in diabetic foot infections, little is known about the pathogenesis of this disease. A model of S. aureus infection in the hindpaw of nonobese diabetic (NOD) mice was developed. The experimental infection was exacerbated in diabetic mice (blood glucose levels ≥19 mmol/l) compared with nondiabetic mice, and the diabetic animals were unable to clear the infection over a 10-day period. Insulin-mediated control of glycemia in diabetic mice resulted in enhanced clearance of S. aureus from the infected tissue. Diabetic mice showed reduced tissue inflammation in response to bacterial inoculation compared with nondiabetic NOD animals, and this was consistent with the novel finding of significantly decreased tissue levels of the chemokines KC and MIP-2 in diabetic mice. Blood from nondiabetic and diabetic NOD mice killed S. aureus in vitro, whereas the bacteria multiplied in blood from diabetic mice with severe hyperglycemia. The impaired killing of S. aureus by diabetic mice was correlated with a diminished leukocytic respiratory burst in response to S. aureus in blood from diabetic animals. This animal model of hindpaw infection may be useful for the analysis of host defects in innate immunity that contribute to recalcitrant diabetic foot infections.