Conclusions This is the first study providing concrete data that 20-kDaPS is a unique polysaccharide molecule discrete from PIA. 20-kDaPS exhibits antiphagocytic properties that may be shown to play a role in pathogenicity. Further work is in progress to establish a role in conjugate vaccine development. Methods Bacterial strains Two reference S. epidermidis strains, ATCC35983 (RP12) and ATCC35984 (RP62A) were used in the present study. Staurosporine Biofilm-producing, PIA-positive S. epidermidis strains 1457, 9142, 8400, and isogenic biofilm-negative,
PIA-negative transposon mutants 1457-M10, M22, M23, M24 and 8400-M10 with Tn917 insertion in the icaADBC operon have been described. In mutants 1457-M10 and M24, Tn917 inserted in icaA whereas in M22 and M23 the transposon inserted in icaC[6, 7, 31, 42, 63]. The transposon was oriented in the same transcriptional AZD1152 clinical trial direction as the icaADBC operon in all mutants except for M24 in which the transposon inserted in the opposite direction. Also, biofilm-negative, PIA-negative
S. epidermidis strains 5179 and 1585 as well as biofilm-positive, Compound C datasheet PIA-negative variant 5179-R1 were used [7, 64, 65] (see also Table 3). Table 3 S. epidermidis reference and clinical strains used in the present study S. epidermidis strains 1457 biofilm+PIA+ ica + 20-kDaPS+ Mack et al., 1992 1457-M10 biofilm-PIA- icaA::Tn917 20-kDaPS+ Mack et al., 1994 M22 biofilm-PIA- icaC::Tn917 20-kDaPS+ Mack et al., 2000 M23 biofilm-PIA- icaC::Tn917 20-kDaPS+ Mack et al., 2000 M24 biofilm-PIA- icaA::Tn917 next 20-kDaPS+ Mack et al., 2000 8400 biofilm+PIA+ ica + 20-kDaPS+ Mack et al., 1992 8400-M10 biofilm-PIA- icaA::Tn917
20-kDaPS+ Mack et al., 1999 9142 biofilm+PIA+ ica + 20-kDaPS+ Mack et al., 1992 5179 biofilm-PIA- icaA::IS257 20-kDaPS+ Mack et al., 1992 5179R1 biofilm+PIA- icaA::IS257 aap + 20-kDaPS+ Rohde et al., 2005 1585 biofilm-PIA- ica- 20-kDaPS- Rohde et al., 2005 ATCC35983 (RP12) biofilm+PIA+ ica + 20-kDaPS+ Reference strain ATCC35984(RP62A) biofilm+PIA+ ica + 20-kDaPS+ Reference strain 1477 biofilm+PIA+ ica + 20-kDaPS+ Clinical strain. 1522 biofilm-PIA- ica- 20-kDaPS+ Clinical strain 1510 biofilm+PIA- ica + 20-kDaPS- Clinical strain 1505 biofilm-PIA- ica- 20-kDaPS- Clinical strain Seventy-five clinical CoNS isolates from blood cultures and central venous catheter tips collected in the Clinical Laboratory of General University Hospital of Patras, Greece, were used in the present study (50 S. epidermidis, 12 S. haemolyticus, 9 S. hominis, 1 S. cohnii, 1 S. xylosus, 1 S. capitis, 1 S. lugdunensis). Clinical strains were identified at the species level (API Staph ID 32 cards and automated VITEK system, BioMerieux) and tested for the presence of icaA icaD1 icaD2 icaC by PCR [66–68]. Ability of clinical strains for biofilm formation was assessed quantitatively on microtiter plates, as previously described [7, 69, 70].