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The effects of extracellular slime from Staphylococcus epidermidis on phagocytic ingestion and killing
J Rodgers1, F Phillips, C Olliff
1Department of Pharmacy, University of Brighton, UK.
Abstract:
Extracellular slime (Ecs) from three strains of Staphylococcus epidermidis was prepared and added to fresh suspensions of polymorphonuclear neutrophils. Phagocytic ingestion and killing of opsonised and unopsonised S. epidermidis strains was assessed over time using slide preparations stained by the Gram's method and microbiological culture. Both phagocytic ingestion and killing were inhibited. Investigation as to one possible mechanism of action of Ecs on phagocytes was performed using 1 mu polystyrene spheres which were incubated overnight with Ecs. It was found that the surface tension was altered with Ecs making the beads more hydrophilic, a factor which may interfere with the phagocytic response to infection.
Insights
Extracellular slime from Staphylococcus epidermidis inhibits neutrophil phagocytosis and killing of bacteria. This slime alters surface tension, potentially interfering with the immune response to infection.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Staphylococcus epidermidis is a common cause of opportunistic infections.
- Extracellular slime (Ecs) produced by S. epidermidis may play a role in immune evasion.
- Polymorphonuclear neutrophils (PMNs) are critical immune cells for combating bacterial infections.
Purpose of the Study:
- To investigate the effect of S. epidermidis extracellular slime on neutrophil phagocytosis and killing.
- To explore a potential mechanism by which Ecs interferes with the phagocytic process.
Main Methods:
- Preparation of extracellular slime from three S. epidermidis strains.
- Incubation of slime with polymorphonuclear neutrophils and opsonised/unopsonised S. epidermidis.
- Assessment of phagocytic ingestion and killing using Gram staining and microbiological cultures.
- Analysis of surface tension changes on polystyrene beads incubated with Ecs.
Main Results:
- Extracellular slime significantly inhibited both the ingestion and killing of S. epidermidis by neutrophils.
- Incubation with Ecs altered the surface tension of polystyrene beads, making them more hydrophilic.
- This change in surface hydrophilicity is a potential mechanism for Ecs-mediated inhibition of phagocytosis.
Conclusions:
- Extracellular slime of Staphylococcus epidermidis actively inhibits key functions of polymorphonuclear neutrophils.
- The alteration of surface properties by Ecs may be a crucial mechanism for S. epidermidis immune evasion.
- Understanding this interaction is vital for developing strategies against S. epidermidis infections.