Lipid S, a novel Staphylococcus epidermidis exocellular antigen with potential for the serodiagnosis of infections

Abstract

We describe the characterisation of a novel glycerophosphoglycolipid (termed lipid S) produced by Staphylococcus epidermidis grown in a chemically defined medium. Lipid S is a short chain length form of the cellular lipoteichoic acid (LTA). It shares common antigenic determinants with LTA, but its chain length of six glycerophosphate units contrasts with 40-42 units in LTA. Lipid S is exocellular and can be recovered from liquid growth medium whereas LTA is associated with the cell wall and membrane. Healthy individuals have low serum levels of IgG against lipid S, but significantly higher titres have been detected in serum from patients with central venous catheter-related sepsis due to coagulase-negative staphylococci and infection of orthopaedic prostheses. An indirect enzyme-linked immunosorbent assay test based on lipid S allows the rapid diagnosis of Gram-positive infection and may have clinical applications in the management of patients with sepsis.

Molecular basis of Staphylococcus epidermidis infections

“…They consist of poly(glycerol phosphate) units, which are substituted at the 2-position of glycerol with alpha-glucose, alpha-glucosamine, D-alanine, or alpha-6-D-alanyl-glucose. Reports on “lipid S”, an alleged pro-inflammatory short-chain form of LTA in S. epidermidis [72], are most likely erroneous and caused by co-purification and misinterpretation of mass spectra originating from a phenol-soluble modulin peptide (PSM-mec) present in MRSE [73]. …”

Rapid serodiagnosis of Staphylococcus aureus surgical site infection following median sternotomy

“…[13][14][15] In brief, the lipid S antigen was prepared from seven pooled strains of CoNS, all isolated from patients with proven staphylococcal infection. Antigen was recovered by gel permeation chromatography (Superose 12) from broth culture.…”

“…We have recently developed a rapid, indirect ELISA incorporating lipid S, a novel exocellular short chain form of lipoteichoic acid probably produced by most strains of staphylococci, for the diagnosis of deep-seated staphylococcal infection. [13][14][15] The ELISA has previously been used to facilitate the diagnosis of central venous catheter related bloodstream infection, 13,14 endocarditis, 16 prosthetic joint infection 17 and pyogenic spondylodiscitis. 18 In this current study, serum antibody levels of anti-lipid S IgG were determined in cardiac surgery patients with clinical and microbiological evidence of S. aureus and CoNS sternal SSI following median sternotomy and compared to patients with no infectious complications following the same type of surgical procedure.…”

The serological diagnosis of staphylococcal infective endocarditis

“…Lipid S is a novel glycolipid antigen, which is released from Gram-positive microorganisms during growth. 13 It is a short chain length form of the cellular lipoteichoic acid found in nearly all pathogenic Gram-positive bacteria.…”