Only 12 strains of 66 corresponded to the ‘classical’ B+P+I+ type. The prevalent type was B−, P−, I+, and it included 24 CoNS of the 66 studied strains. Despite the presence of ica genes in several species, no PNAG was detected in vitro. The inactivation of the ica operon could be attributed to several factors such as the insertion of the IS256 element (Ziebuhr et al., 1999), the action of the IcaR repressor (Conlon et al., Ivacaftor 2002), and post-transcriptional regulation (Knobloch
et al., 2002). Factually, the maximum transcription of icaADBC can be obtained with a persistence of PNAG and a biofilm-negative phenotype (Dobinsky et al., 2003). The reason for the absence of biofilm production Idasanutlin order despite the presence on the entire ica operon remains
unclear. Similar results were obtained in the ica operon expression studies on 10 strains of S. epidermidis (seven biofilm-positive and three biofilm-negative strains) (Cafiso et al., 2004). Because the strains were isolated from patients with infected implanted devices, PNAG and biofilm may be formed in vivo, but not in vitro. The two types of strains B+, P−, I+ (eight of 66 CoNS strains) and B+, P−, I− (two Staphylococcus lugdunensis of 66 strains) are very interesting, because they imply a possibility that different CoNS species could form a biofilm in vitro not containing PNAG. Selected biofilm-positive strains of this collection were then used for a detailed chemical analysis of their EPS. Having established the reliable method of analysis of the extracellular matrix of a staphylococcal biofilm (Sadovskaya et al., 2005), our group investigated the chemical composition of carbohydrate-containing polymers of a number of biofilm-positive staphylococcal
strains associated with the infections of orthopaedic implants (Kogan et al., 2006; Sadovskaya et al., 2006). Of the 15 biofilm-producing clinical staphylococcal strains studied, three produced high amounts of PNAG in vitro. The production of PNAG by one of them, S. epidermidis 5 (CIP 109562), was higher than that of the model strain S. epidermidis Montelukast Sodium RP62A, and therefore, this strain may be considered as a PNAG overproducer (Fig. 2a and b). Three strains (two S. epidermidis and one S. lugdunensis) were found to produce a small, but detectable amount of PNAG (Fig. 2c). Nine other strains (six S. epidermidis and one of each S. aureus, Staphylococcus warneri, and S. lugdunensis) did not produce in vitro PNAG in an amount that could be detected using direct chemical methods (Fig. 2d). While the presence of trace amounts of PNAG cannot be excluded, we suggested that biofilms of these strains contain mainly TA and protein components, which could be easily isolated from their extracellular extracts.