Mtcc 96

The drug-sensitive strain MTCC 96 (ATCC9144) of S. aureus was procured from the Microbial Type Culture Collection, CSIR-Institute of Microbial Technology Chandigarh, India. Clinical isolates of S. aureus were obtained from Dr. K. N. Prasad (Laboratory of Clinical Microbiology, SGPGIMS, Lucknow, India) (Gupta et al., 2012 (link)). Standard Mueller-Hinton agar and cation-adjusted Mueller-Hinton broth media (MHA and MHB, Hi-Media, Mumbai, India) were used to culture bacteria. Tryptic soy broth (TSB, Hi-Media, Mumbai, India) medium was used for Biofilm assays. Glabridin, antibiotics, phosphate-buffered saline, DMSO, glucose and lysostaphin was procured from Sigma-Aldrich (St. Louis, MO, United States). Crystal Violet used in this study was used from Hi-Media (Mumbai, India). Trypsin Gold, Mass Spectrometry Grade was obtained from Promega (Madison, WI, United States). Taq DNA polymerase master mix, c-DNA synthesis kit and SYBR Green qPCR super mix was purchased from Genetix (Thermo, United States).

The effect of isolated compounds on the morphology of MDR S. aureus strains was observed under scanning electron microscopy (SEM) after the bacterial cells were treated with the isolated compounds (arborine and skimmianine) for 6 h. After the treatment, 1 ml of each test bacterial strain was collected, centrifuged, and washed three times with phosphate buffer saline and incubated for 30 min at 4°C and fixed with 2.5% glutaraldehyde. The MDR S. aureus cells were dehydrated in ethanol, freeze-dried under vacuum condition, coated with an ion sputtering apparatus, and observed through SEM (Hitachi S-3400N). All strains of MDR S. aureus cells that are not exposed to the isolated compounds and a standard reference strain of S. aureus (MTCC 96) [procured from Microbial Type Culture Collection and Gene Bank (MTCC), Institute of Microbial Technology, Chandigarh, India] cells were similarly processed and used as controls (29 (link)).