MRSA or methicillin-resistant Staphylococcus aureus are bacteria which are resistant to many antibiotics and difficult to treat. MRSA can cause infections in skin and soft tissue. These can be acquired from hospitals and community. From community, it requires direct contact with the boils or lesions of the affected person. If you kiss someone who has boils or lesion on lips or mouth areas then you can get this infection. If a person is having MRSA on other areas of the body and you did not touch the wound then chances of MRSA transmission are poor.
You can still kiss the person as long as they don't have it on their mouth or face. Just make sure if you guys are going to be doing some sexual activies. The person should cover up his/her open wounds to prevent the spread of it.
I would not under any circumstances have an open mouth with tongues locked. MRSA is highly contagious and you are running a big risk even kissing. If you have the tiniest cut or abrasion min your mouth the MRSA virus will find it's way in. Be Careful!