Is mrsa deadly? what could cause it to become deadly?

Yes it can be: Mrsa can be deadly if you have a serious infection because it is resistant to most antibiotics. It becomes deadly when the infection spreads throughout the whole body. On the other hand, people can carry MRSA and not be affected at all.

Bacterial Infection: Methicillin-resistant staphylococcus aureus (MRSA) is a bacterial infection that cannot be treated/ cured with certain antibiotics. These infections can be severe and may require more invasive techniques to treat. If you are given antibiotics, be sure to take all the doses, even if you feel better. Please see your doctor for treatment!

Mrsa varies: A mrsa skin infection can usually be easily treated. If mrsa gets into the blood stream ( patient becomes septic) it can be a very serious infection.