The antibiotics will kill all the bad bacteria that might cause infection, also all the good bacteria that your body needs to function, particularly for digestion. Be sure to take probiotics to restock the beneficial bacteria in your gut. Live culture buttermilk is also good as is any fermented food like sauerkraut.
My husband had hip replacement about 2 months ago. The medications they gave him totally screwed up his system. He had indigestion so bad, that it felt like a heart attack. It has taken weeks to get him back in some form of good health, still working on it.