Commensal bacteria

Commensal bacteria are bacteria which are normally present on the skin or mucous membranes which usually don't cause disease, but can cause disease in compromised humans. They're often implicated in nosocomial infections.

These bacteria are usually part of the normal microflora, and they contribute to the body's defence against intruders. These bacteria co-evolved with humans and are usually beneficial, but can, under certain conditions, overcome the body's defences and cause disease.

Some examples of commensal bacteria include:

• Staphylococcus epidermidis and other staphylococci (not aureus)
• Propionibacterium
• Corynebacterium