Opsonophagocytosis of Staphylococcus aureus by diabetics' sera and monocytes

The ingestion and the intracellular killing of Staphylococcus aureus by monocytes from patients with noninsulin-dependent diabetes mellitus (NIDDM) under good control (mean 2-h postprandial blood glucose less than 150 mg/dl in the past 6 months) or under poor control (mean 2-h postprandial blood glucose greater than 200 mg/dl in the past 6 months) were investigated. The ingestion was expressed as a phagocytic index which was a percentage of the total bacteria added in the reaction mixtures, while the intracellular killing was expressed as the percentage of ingested bacteria which were destroyed. The phagocytic index (mean +/- S.E.) of healthy subjects (HS), diabetics under good control (DGC) and diabetics under poor control (DPC) were 45.1 +/- 3.5, 38.2 +/- 2.2, and 32.1 +/- 3.4%, respectively. This showed that monocytes from diabetics ingested S. aureus more poorly than did those from HS (p less than 0.001) and monocytes from DPC ingested more poorly than did those from DGC (p less than 0.001). There was no difference in intracellular killing between HS and DGC, but a marked difference was noted between DGC and DPC. Specific antibodies (IgG) as demonstrated by indirect immunofluorescence assay had little effect on ingestion but could enhance complement activation and then increase ingestion whether the serum was from HS, DGC, or DPC. On the other hand, the significant effect of complement activity in the presence of specific antibodies on intracellular killing was only observed on HS and DGC, suggesting that antibody-dependent complement activation could be a crucial mechanism for efficient intracellular killing.(ABSTRACT TRUNCATED AT 250 WORDS)