Health chiefs in Scotland said yesterday that there had been no new cases of the so-called "superbug" which stopped all heart operations at Edinburgh's main hospital last week.

Surgeons were told to postpone operations at Edinburgh Royal Infirmary on Friday after all 13 patients in the cardiac unit were found to have contracted MRSA, which can cause blood infections or pneumonia.

The hospital confirmed that no one else had been found to be suffering from the bug, which can enter the blood stream through open wounds.

Those already infected were said to be in a stable condition. Nine had developed signs of infection while the other four were said to be carrying the organism but had yet to develop symptoms.

A spokeswoman for the hospital trust said that the infection outbreak had not spread beyond the intensive care unit, which is used for cardiac surgery.

All non-urgent cardiac surgery scheduled for this week at the hospital was suspended and an investigation was launched after the MRSA cases were confirmed.

MRSA usually affects people having hospital treatment although, less commonly, people outside can also contract it. MRSA is described as a superbug because of its resistance to treatment with commonly used antibiotics.

Preliminary examinations have not indicated that cleanliness was a factor in the outbreak at the hospital.