Paper Title
Phagocytosis Of S. Epidermidis Biofilm By Neutrophil: A Comparative Study Of Planktonic And Biofilm Killing

Abstract
- Staphylococcus epidermidisis is an opportunistic pathogen and common gram positive micro-flora of human skin which causes infection in its biofilm mode of growth. The S. epidermidis strains are often gain resistance to common antibiotics in its biofilm life style. The interaction of biofilm residing S. epidermidis with human immune response particularly with polymorphonuclear neutrophil (PMN), a cell of innate immunity system which non-specifically eradicates the bacterial infection by the process of phagocytosis and killing, is poorly understood. In the present study the quantitative assay for the measurement of phagocytosis and killing of S. epidermidis by Human PMN was carried out. The autologous serum was isolated by centrifugation from human blood and S. epidermidis was opsonised with the isolated autologous serum. Human PMN was isolated from whole venous blood by using PolymorprepTM and re-suspended in HBSS buffer followed by incubation at 370C with autologous serum. PMN and opsonised S. epidermidis was co-incubated for different time periods of 5-40 min. The phagocytic activity of PMN was accessed by quantifying the PMN intracellular bacterial count by CFU counting assay in manitol salt agar plate. After differential centrifugation extracellular and intracellular bacteria was quantified. The data showed that Intracellular bacterial count was highest at 5 minutes and then start decreasing in time dependent manner with the reduction in extracellular bacterial count. Key words- PMN, Biofilm, Opsonisation, Phagocytosis.