I Am 84...female... Had UTI But Allergic To Almost All

I am 84...female... had UTI but allergic to almost all antibiotics. Doc ordered cranberry capsules and lots of water which has helped.... I have also begun eating more meat .... stool is now NOT BLACK but much darker brown than usually was when I was just eating peanut butter and chicken. Would change in diet and the cranberry capsules cause this change?