Coloured scanning electron micrograph (SEM) of a neutrophil (white blood cell, blue) interacting with Klebsiella pneumoniae bacteria (orange). Klebsiella is commonly found in human intestines and under normal conditions does not cause any harm. It can cause severe opportunistic infections however, especially in people receiving certain hospital treatments. These infections include pneumonia, meningitis, blood infections and infections of surgical wounds. It is resistant to multiple drugs, but infections can be treated with certain antibiotics.