Over the years, this polysaccharide has been referred to as a PS/A by this research group. Later, Christensen et al. (1990) described a slime-associated antigen (SAA) isolated from the same strain and having a similar function. SAA was claimed to be different from PS/A. However, Baldassari et al. (1996) suggested that SAA and a hexosamine-containing polysaccharide intercellular adhesin (PIA) of S. epidermidis strains RP62A and 1457, Selleckchem RXDX-106 described at that time by Mack et al. (1994), could be the same antigenic molecule. Mack et al. (1996) were the first to elucidate the chemical structure of PNAG (called, according to its biological properties, PIA). Using a combination

of analytical methods and nuclear magnetic resonance (NMR), PIA was identified as a linear β(1,6)-linked N-acetylglucosaminoglycan containing c. 130 N-acetylglucosamine (GlcNAc) residues, partially substituted with O-succinyl groups, partially de-N-acetylated and apparently phosphorylated (Mack et al., 1996). The genes encoding PNAG biosynthesis are

organized in the icaADBC (intercellular adhesion) operon, which consists of four ORFs (Heilmann et al., 1996; Gerke et al., 1998) with a transcriptional repressor gene, icaR, located upstream and transcribed in the opposite orientation (Conlon et al., 2002). The ica locus was later found in a number of S. aureus strains, and its presence was related to the ability to form a biofilm in vitro (Cramton et al., 1999). A recombinant Saracatinib strain of Staphylococcus carnosus (pCN27), containing icaABC of S. epidermidis RP62A, unlike the parent S. carnosus strain, which is biofilm-negative, was adherent to glass and revealed the ability to form intercellular aggregates as well as to produce PNAG (Heilmann et al., 1996). McKenney et al. (1998) subsequently demonstrated that the recombinant S. carnosus (pCN27) antigen was identical to PS/A and ‘chemically related’, but distinct from PIA in molecular size, solubility, and substitution of the majority of the amino groups of the glucosamine residues with succinate. This polymer,

named poly-N-succinyl-β-(1,6)-glucosamine (PNSG), was suggested as a potential vaccine candidate against staphylococcal infections (McKenney et al., 1999, 2000). However, Meloxicam subsequent studies carried out by the same group showed that the presence of the N-succinyl substitution was an analytical artefact (Joyce et al., 2003). These authors used a ‘PS/A overproducing strain’S. aureus MN8m, and the corresponding polysaccharide was named SAE (S. aureus exopolysaccharide). Detailed NMR studies, in combination with the chemical modifications, allowed a complete assignment of NMR spectra of SAE. According to Joyce et al. (2003), the main differences between SAE and PIA were phosphorylation (absence of a phosphate substitution in SAE) and molecular mass [>300 kDa for SAE and ∼30 kDa for PIA (Mack et al.