How does vancomycin affect the gut microbiome? thank you?

Vancomycin taken by mouth gives significant concentration to kill bacteria like Clostridium difficile which causes enterocolitis(small intestine and large intestine inflammation),some times other bacteriae like staphylococcus aureus causing enterocolitis. Injection form of vancomycin doesn't get enough concentration in the gut to kill the bacteriae.

Vancomycin given orally is one of the antibiotics which works to rid the body of unwanted organisms in the gut such as clostridioides dificile. It does not affect the gut at all if given intravenously. See you’re treating doctor or a gastroenterologist if you have persistent bowel symptoms. Good luck.