Neutrophil function in gram-negative rod bacteremia. The interaction between phagocytic cells, infecting organisms, and humoral factors.

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Abstract

To assess the phagocytic and bactericidal function of neutrophils in the acute stages of gram-negative rod bacteremia, cells from 30 nonleukopenic patients were studied in a test system utilizing plasma obtained simultaneously with culture-positive blood, the autologous infecting strain, and two laboratory test strains of Staphylococcus aureus and Pseudomonas aeruginosa. Results were compared to those obtained with normal neutrophils and plasma. Patient and control plasma were simultaneously tested with each source of phagocytic cells to localize any abnormalities. Four patients had a defect against their infecting strain, 33% of the inoculum phagocytized and killed versus 80% by controls. In these cases differences were localized to the patients' plasma, as normal plasma tested with patients' cells reversed the defect. Thus, four patients had impaired opsonization when compared to normal controls, but we also observed that 11 of 30 bacteremic isolates, all Escherichia coli, showed absolute or relative resistance to phagocytosis in the patient and control assay system. No intrinsic granulocyte killing abnormalities were noted. There was poor correlation between results obtained with infecting strains compared to laboratory test organisms. We conclude that in patients without evidence of an inherited neutrophil bactericidal disorder, recurrent infection, or treatment with cytotoxic drugs, intrinsic bactericidal defects are uncommon at the onset of gram-negative bacteremia, and impaired opsonization is the most commonly encountered cause of neutrophil dysfunction.

Authors

R J Weinstein, L S Young