A spokeswoman for the hospitals said that cases of both VRE (vancomycin resistant enterococcus) and MRSA (methicillin resistant staphyloccus aureus, also known as golden staph) were identified in a ``number of patients'' at both hospitals.

The Sydney Morning Herald reported that 13 Royal North Shore Hosptial patients had VRE, and that it was life-threatening.

But the spokeswoman for the St George and Sutherland hospitals said most major hospitals would at any one time have patients who had VRE.

"Many patients with VRE have been identified as carriers prior to their admission to hospital and appropriate infection control measures are put in place when they are admitted to reduce the risk of transmission,'' she said.

Enterococci are generally harmless bacteria that live in the intestines of most people. VRE has become resistant to and can't be destroyed by many antibiotics, including the vancomycin, which is commonly called ``the antibiotic of last resort''.

VRE can be detected only by laboratory testing.

It can lead to infection, causing the patient to become ill, or to colonisation, which makes the patient a carrier without becoming sick from it.

The hospitals' spokeswoman said it was not always possible to determine whether patients had acquired VRE or MRSA while they were in hospital.

"The single best method to prevent the spread of both VRE and MRSA is vigilant hand washing, particularly in the hospital setting,'' she said.

"The hospital's primary aim is to stop the spread of VRE and MRSA to other patients.''