Figure 7 Induction of capsule production by IPTG in S. aureus Newman-132. CP5 was labelled by immunofluorescence (CY3, green), the cells were stained using DAPI (blue). Cells were grown for 6 h in MH medium at 37°C. a) S. aureus Newman (control) b) S. aureus Newman in the presence of 0.5 mM IPTG; c) S. aureus Newman-132 harbouring pMUTIN4 in the capsule
promoter in the absence of IPTG and d) S. aureus Newman-132 harbouring pMUTIN4 in the capsule promoter after induction with IPTG. As capsule production in SA1450/94 might be impaired by the insertion of IS256 described above, it was attempted to reconstitute CP5 production. In S. aureus Newman insertion of Tn916 into cap5A1 could be repaired by complementation of cap5A1 in selleck trans . Therefore, a similar construct (pCapAre) was introduced into SA1450/94, which increased capsule production compared to the parent strain (Figure 8). However, full capsule production was not achieved and the vancomycin MIC of the MK-8931 chemical structure clone remained unchanged compared to SA1450/94. Figure 8 Capsule production of different S. aureus SA1450/94 clones. CP5 was labelled by immunofluorescence (CY3, green), the cells were stained using DAPI (blue). Cells were grown for 6 hours in BHI medium at 37°C. a) S. aureus SA1450/94 harbouring pCapAre, which has reconstituted capsule production; b) SA1450/94 (control)
and c) SA1450/94 harbouring pCU1 (vector control). Furthermore, a capsule knockout mutant of strain Reynolds had previously
been Vorinostat tested against vancomycin, and no differences in susceptibility to vancomycin were recorded . Population analyses in our laboratory confirmed this result (data not shown). Effect of capsule material on the susceptibility of staphylococci to vancomycin In order to test whether capsule material Resminostat is able to interact with or bind to vancomycin, crude capsular material was prepared from S. aureus 137/93G and S. aureus NCTC 8325 (negative control; as shown in Figure 6 for S. aureus HG001, the strains of this lineage do not produce a capsule unless cap5E is repaired). Cell wall teichoic acid that might contaminate the extracts was removed by periodate oxidation. The material was added to MIC determinations using S. aureus NCTC8325 and S. aureus SG511 as indicator strains in MH medium. There was no significant difference in the MIC values between the extract containing capsular material and the controls for S. aureus SG511, however a small effect (0.7 mg/L increase in the MIC) was visible with S. aureus NCTC8325 and the extract of S. aureus SA137/93G. The test was repeated 8 times with two different preparations of the capsular material; an additional DNase and RNase digest did not influence the result. While we cannot explain this difference, the fact that no increase in the MIC was visible with the more susceptible indicator strain strongly indicated that the type 5 capsular material did not neutralise the effect of vancomycin in this assay.