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	Please give me a concise synopsis of GISA, easy for students to remember.
	The description below is pretty concise & simple. I am not sure what level student this explanation will be provided. I hope it helps. GISA stands for glycopeptide intermediate Staphylococcus aureus. The glycopeptides antimicrobial agents are vancomycin and teicoplanin. Since only vancomycin is used in the United States GISA is often referred to as VISA. The S. aureus isolates become GISA or VISA after prolonged exposure to vancomycin during therapy. VISA isolates have a thickened cell wall, which is predicted to be the mechanism of reduced susceptibility to vancomycin. Vancomycin is a cell wall active antimicrobial agent and it is hypothesized that the tickened cell wall may either increase the number of vancomycin-binding targets so that higher concentrations of vancomycin would be needed for antimicrobial activity or the thickened cell wall may obscure the vancomycin target which would also limit the antimicrobial activity. The cellular changes that result in the thickened cell wall are not well understood.

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