Loss of resistance to methicillin and other antibiotics in Staphylococcus aureus associated with a chronic empyema.

A chronic empyema was investigated in a patient during a period of seven years. A strain of Staphylococcus aureus resistant to methicillin and four other antibiotics was isolated and the loss of all these determinants was shown to occur in vitro. A similarly sensitive organism was obtained directly from the patient during the later stages of his illness and the homogeneity of the phage patterns indicate that the organism was a true variant which evolved from the highly resistant one.