There is no term like mercer in medicines. People don't pronounce correctly. Proper word is MRSA or Methicillin resistant staphylococcus aureus. These are bacteria which can be acquired from hospitals and community. These causes infections on skin but sometimes, enter the blood and can cause infection in different organs like lungs, bones, liver, spleen etc. MRSA can attack on lungs causing pneumonia. It requires treatment with antibiotic shots. Patient needs hospitalization and ventilation for breathing. Use of steroids is also recommended.