At the time Jorge Bergoglio was a teenager, most lung surgery was done for infections, especially tuberculosis (TB) and empyema, a condition related to pneumonia where pus accumulates between the lung and the chest wall.

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"If you have somebody who has an infection -- he has a draining infection -- and he gets some of his pus on a bench, that staph's going to be there for hours or days before it dries out, " he said.

CNN: NFL stars no match for bacteria

Most MRSA infections acquired in community settings present themselves as sores or boils and often appear red, swollen, painful or with drainage such as pus, the CDC says.

CNN: NFL stars no match for bacteria