
Staphylococcus aureus (S. aureus) can colonize the upper respiratory tract of around one quarter of the human population. As an opportunistic bacteria S. aureus usually does not harm its host. If the host is healthy and the bacteria obtain sufficient nutrients, the bacteria remain quiet and are kept under control by the immune system. They may, however, become active in response to infections by another pathogen or illness weakening the host immune system.











