Pneumonia that is caused by Staphylococcus aureus and is resistant to methicillin treatment. [ NCI ]. The disease or phenotype is Methicillin-Resistant Staphylococcus Aureus Pneumonia (EFO_0008556, an Experimental Factor Ontology entry). Also known as: MRSA Pneumonia, Methicillin-Resistant Staphylococcus aureus Pneumonia.