September 16, 2013
Sinead M. Ni Chadhain
The questions this paper asks are what effect does Oritavancin activities have on S. aureus in slow growing and biofilm states. What causes microbes to be resistant to some antimicrobial agents? How does Oritavancin work that it has had better results than vancomycin, along with other antimicrobial agents?
The author linked his/her work to previous research by telling us what the drug Oritavancin is and how it works such as, the activity that it exhibits in certain infections that it has already been tested on. They also tell us that Oritavancin has multiple mechanisms of action, what distinguishes it from ...view middle of the document...
In another experiment with MRSA and VRSA with Oritavancin limited growth occurred in nutrient depleted CAMHB over 24H. Vancomycin achieved some killing in stationary phase against MRSA but not VRSA in nutrient depleted CAMHB in 24 h. Daptomycin and rifampin exhibited expect results against MRSA in the stationary phase in 24 h, but no killing in VRSA. The bacteriostatic agent had no effect on cell numbers in either strand in 24 h. The estimated free trough concentrations of Oritavancin reduced cell counts but the estimated free trough concentration of vancomycin and daptomycin had no effect on the cell counts. Oritavancin has an effect of membrane integrity. The rapid bactericidal activity in the exponential phase is parallel with the membrane depolarization and the increased membrane permeability. Fluorescent probes were used to determine if oritavancin showed these same effects in the stationary phase. This showed a breakdown of the membrane potential because of an increase in the fluorescence. The rate of release of dye was less in the stationary phase than during the exponential phase, but there was still some release in the stationary phase. During this experiment, vancomycin had no effect and daptomycin had little effect in the exponential phase, but none in the stationary phase. In another experiment time-kill studies using membrane assay buffers show the same results as the fluorescent experiment. Oritavancin targets the septum of stationary phase MRSA ATCC 43300 cells. Observed septal deformations and a loss of staining of the nascent septal cross wall, and midline in exposed cells with Oritavancin but these effects were not seen with vancomycin. Staining of the midline was absent...