What Causes Klebsiella Pneumoniae Infection?

I HAVE BEEN BEING TREATED FOR E.faecium WITH CUBICIN FOR OVER A WEEK AND THE CULTURE CAME BACK TODAY SHOWING THAT IT IS GONE BUT I NOW HAVE TWO OTHER BACTERIAS!!!! KLEBSELLA PNEUMONIAE AND CITROBACTER FARMERI WHICH THEY WANT TO TREAT WITH ROCEPHIN. NOW I KNOW I GOT THE E.faecium FROM MY HOSPITAL SURGICAL VISIT IN JANUARY BUT WHY DO I NOW HAVE TWO NEW ONES??????