Genomic DNA was isolated from R16-18d and the sequence of the 16s rRNA gene was determined to be identical to the sequence from NCTC 8325-4 and RRSA16 as described above.

MICs were determined on microdilution plates according to Wiegand et al. (2008) using CAMHB2 as the growth media. Sodium chloride was added to a final concentration of 2% (w/v) when oxacillin was tested. BSA (0.02% w/v) was added to media when vancomycin, ramoplanin or nisin was tested to prevent peptide adhesion to polystyrene. Doubling times were calculated as described (Cui et al., 2003), with tryptic soy broth (TSB) cultures growing APO866 mw at 37 °C with aeration in the exponential phase [Eqn. (1)], where t1 and t2 are the times of measurement: (1)

Staphylococcus aureus cultures were grown in TSB supplemented with 0.02% BSA (TSB+BSA) at 37 °C with shaking at 200 r.p.m. to OD620 nm≈0.4 and were then treated with an antibiotic. The cultures were then incubated at 37 °C with shaking at 200 r.p.m. Samples were removed periodically for OD measurements and viable counting. Staphylococcus aureus cultures were grown in TSB+BSA at 37 °C with aeration to an OD620 nm of ≈0.7. Samples were removed, pelleted and resuspended in 4% glutaraldehyde. The pellets were washed twice in 0.1 M sodium cacodylate buffer containing 7.5% sucrose and pre-embedded in 1% agar. The samples were washed twice with selleck kinase inhibitor 0.1 M sodium cacodylate buffer containing 7.5% sucrose and postfixed in 1.0% osmium

tetroxide 4-Aminobutyrate aminotransferase in 0.15 M sodium cacodylate buffer. Samples were washed for 10 min twice in 0.11 M veronal acetate buffer. Samples were then dehydrated in an ascending ethanol series and embedded in Epon resin. Sections were cut at 80 nm on a Reichert Ultracut S ultramicrotome and mounted on copper rhodium 200 mesh 3 mm grids. Samples were stained with uranyl acetate for 30 min, rinsed three times in distilled water, stained with Reynold’s lead citrate stain prepared as described by Venable & Coggeshall (1965) for 5 min and rinsed three times in distilled water. Samples were viewed using a Philips/FEI CM12 transmission electron microscope at 80 kV. Cell wall thickness was calculated as described elsewhere (Cui et al., 2000). Twenty radial lines arranged regularly at angles of 18° were placed over the center of images of equatorially cut cells at a final magnification of × 35 000 and the thickness of the cell wall was measured from at least 10 different points. The thickness of the cell walls of 20 cells from each strain was measured. Results are reported as means±SD. The diameter of the 20 cells from each strain was also measured using 20 radial lines arranged regularly at angles of 18° and placed over the center of equatorially cut cells; the results were reported as means±SD. The statistical significance of the data was evaluated using a Student’s t-test.