Coloured transmission electron micrograph (TEM) of a human neutrophil (red) containing ingested a Klebsiella pneumoniae bacterium (purple). 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. Neutrophils have several roles in the bodys immune response, one being phagocytosis (ingestion) of foreign material such as this bacterium.