Bactericidal Capacity of Neutrophils in Rabbits with Experimental Acute and Chronic Abscesses

Bacteria persist within abscesses despite the presence of neutrophils, and patients with abscesses have high rates of subsequent infections. A model was developed to study neutrophil function in rabbits with Staphylococcus aureus abscesses. Blood neutrophils from rabbits with 2-week-old (chronic) abscesses had diminished bactericidal capacity and decreased superoxide production compared with rabbits with 24-h (acute) abscesses. Rabbits with chronic abscesses did not produce serum opsonic factors that enhanced bacterial killing. A bactericidal assay performed with chronic abscess fluid in the suspending medium revealed inhibition of neutrophil killing. The inhibition could be replicated with a neutrophil lysate but not by an S. aureus supernatant. Rabbits with chronic abscesses have diminished blood neutrophil bactericidal capacity and superoxide formation, and the abscess fluid milieu is inhibitory to neutrophil function.