Should I be concern because a co-worker has mrsa?

Mrsa . Mrsa is passed by direct contact. The risk with casual contact is very low with good hygiene. There must be prolonged skin to skin contact.
Wash your hads. Mrsa is likely more common than we think in healthy people. With a known carrier... Wash your hands, wash your hands, wash your hands. And minimize touching your face/nose. If you need to scratch... Use the back of your hand/forearm.