Pathogenic streptococci produce streptolysin . Streptolysin O binds to cholesterol in membranes. The effect on neutrophils is to cause lysosomal granules to explode, releasing their contents into the cell cytoplasm. Pathogenic staphylococci produce leukocidin , which also acts on the neutrophil membrane and causes discharge of lysosomal granules. Killing Phagocytes After Ingestion .
Some bacteria exert their toxic action on the phagocyte after ingestion has taken place.
They may grow in the phagosome and release substances which can pass through the phagosome membrane and cause discharge of lysosomal granules, or they may grow in the phagolysosome and release toxic substances which pass through the phagolysosome membrane to other target sites in the cell. The foregoing has been a discussion of the most commonly-employed strategies of bacterial defense against phagocytes. Although there are few clear examples, some other antiphagocytic strategies or mechanisms probably exist. For example, a pathogen may have a mechanism to inhibit the production of phagocytes or their release from the bone marrow. A summary of bacterial mechanisms for interference with phagocytes is given in the following Table.