Staphylococcus aureus bacteria dividing, coloured transmission electron micrograph. At lower left is a single bacterium, the bacterium at upper centre is starting to divide, and at lower right a new cell wall has divided the bacterium into two, which will then separate. This bacterium is a normal part of the skin and mucous membrane flora in humans, although it can cause food poisoning in some cases, and can also infect wounds and even cause potentially fatal diseases such as meningitis, pneumonia and septicaemia. Infections can usually be treated with antibiotics, although some strains, such as methicillin-resistant S. aureus (MRSA) are resistant to many antibiotics.