Many thanks for posting your query here at healthcaremagic.
Many healthy people carry this bacteria - Staphylococcus Aureus
. It is usually commensal organism, which means it remains with us without causing any symptoms.
It is usually found in skin/nose etc and we may never find out if we don't test for it. Even negative test doesn't rule out that this or other bacteria are not living/thriving on us.
The fact that your baby has been healthy and no symptoms have been noticed is really reassuring.
Doctors are more worried if the Staphylococcus bacteria which they have grown in laboratory is resistant to many antibiotics including Methicillin and is difficult to kill. This is commonly known as MRSA - Methicillin Resistant Staph Aurues.
I hope I've been able to reassure you regarding your concerns
Dr Tejas Shah