Antibacterial Action of Extracellular Mammalian Group IIA Phospholipase A2 against Grossly Clumped Staphylococcus aureus

Abstract

Fibrinogen-dependent interactions of Staphylococcus aureus are believed to contribute to bacterial virulence by promoting bacterial attachment to fibrinogen-coated surfaces and inducing the formation of bacterial clumps that are likely resistant to phagocytosis. Although S. aureus produces several fibrinogen-binding proteins, the cell wall-associated protein clumping factor (encoded by clfA) appears to be most important in bacterial interactions with immobilized or soluble purified fibrinogen. We have compared bacterial clumping in several strains of S. aureus, including isogenic ClfA+ and ClfA− Newman strains, in the presence of purified rabbit fibrinogen, human plasma, and inflammatory fluid and examined the effect of clumping on bacterial sensitivity to mammalian group IIA phospholipase A2 (PLA2). This enzyme is the major extracellular bactericidal agent in inflammatory fluid active against S. aureus. Both ClfA-dependent and ClfA-independent bacterial clumping was observed, depending on the source and fibrinogen content of the biological fluid. In each case, clumping only partially reduced the antibacterial activity of PLA2, suggesting that this extracellular enzyme can substantially penetrate dense bacterial clumps. Bacterial clumps could be dispersed by added proteases, restoring full antibacterial activity to PLA2. Thus, the extracellular mobilization of group IIA PLA2 during inflammation may provide a mechanism by which the host can control the proliferation and survival of S. aureus even after bacterial clumping.

Possible virulence factors of Staphylococcus sciuri

“…Still, it is possible that S. sciuri could agglutinate erythrocytes of sheep or some other animal species, as it was described for Staphylococcus saprophyticus isolates [26]. The ability of S. aureus to initiate colonization by attachment to ¢brinogen-containing substrates, and to clump in the presence of ¢brinogen and thus increase resistance to phagocytosis, is primarily due to the presence of clumping factor [32,33]. S. epidermidis, and most other CoNS do not produce clumping factor [15].…”

“…The ability of S. aureus to initiate colonization by attachment to fibrinogen‐containing substrates, and to clump in the presence of fibrinogen and thus increase resistance to phagocytosis, is primarily due to the presence of clumping factor [32,33]. S. epidermidis , and most other CoNS do not produce clumping factor [15].…”

The fibronectin binding proteins of Staphylococcus aureus are required for adhesion to and invasion of bovine mammary gland cells

“…Clumping of S. aureus mediated by host proteins is considered to be a virulence property [14,15]. Clumping may be of advantage to the bacteria by reducing their susceptibility to host defense mechanisms such as phagocytosis and killing by phospholipase A [16]. Moreover, in vivo aggregates of bacteria were also observed in heavily infected bovine mammary glands [2].…”

The fibronectin binding proteins of Staphylococcus aureus are required for adhesion to and invasion of bovine mammary gland cells

“…Clumping of S. aureus mediated by host proteins is considered to be a virulence property [14,15]. Clumping may be of advantage to the bacteria by reducing their susceptibility to host defense mechanisms such as phagocytosis and killing by phospholipase A [16]. Moreover, in vivo aggregates of bacteria were also observed in heavily infected bovine mammary glands [2].…”