What is Nitrofurantoin? Nitrofurantoin, sold under the trade name Macrobid among others, is an antibiotic used to treat bladder infections. It is not effective for kidney infections. It is effective against E. Coli, Enterobacter cystitis, Enterococcus, Klebsiella, and Staphylococcus aureus. Nitrofurantoin interferes with the production of bacterial proteins, DNA, and cell walls. Bacteria cannot survive without a cell wall or multiply without DNA.