Direct observations by phase microscopy have demonstrated that small numbers of pathogenic staphylococci survive prolonged periods of time within living human polymorphonuclear leukocytes. Non-pathogenic microorganisms are rapidly destroyed in similar preparations.

Leukocytes in which staphylococci remained viable often appeared less vigorous after ingesting microorganisms, but intracellular survival could not be correlated with obvious leukocyte damage with any consistency.

Both pathogenic and non-pathogenic cocci were seen to divide within living granulocytes during the first few minutes after ingestion. Occasionally pathogenic staphylococci multiplied in dying cells after long periods of intracellular residence.

Phagocytosis of more than one pair of staphylococci by a single leukocyte appeared to act as a stimulus to bacterial destruction. Multiple ingestions of pathogenic staphylococci reduced the incidence of survival of the total microbiol population contained within the cell.

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