Visualization of capsular polysaccharide of coagulase negative staphylococci (CNS) associated with vascular prosthetic graft material

Abstract

The coagulase negative staphylococci (CNS) are a ubiquitous group of microorganisms which comprise a major component of the microbial flora of the skin and adjacent glands. Historically, the CNS were viewed as insignificant contaminants with little clinical importance. However, over the last decade these organisms have emerged as important etiologic agents of biomaterial associated infections. Furthermore, many of the Staphylococcus epidermidis strains recovered from catheter or prosthetic infections exhibit the capacity to produced an extracellular capsular polysaccharide (slime) which is viewed as an important factor in biomaterial adherence and persistence. Bacterial capsular material is composed of hydrated polysaccharides and has been visualized by transmission electron microscopy when lysine is added to the fixation protocol. This study reports on the use of a lysine-ruthenium redglutaraldehyde fixation technique for visualizing the polysaccharide capsule on two coagulase negative staphylococcal reference strains, S. epidermidis RP62A (ATCC 35984) and S. hominis SP2 (ATCC 35982).