An outbreak of a multi-drug resistant organism at Middlemore Hospital's National Burns Centre has infected three already very sick patients.

Three patients in the unit at Middlemore Hospital have fallen ill with carbapenem-resistant organisms.

These organisms are part of the normal human gut bacteria, which can become resistant to the powerful carbapenem antibiotics often relied on for infections.

The infection was first found on 10 December, with the most recent being discovered on Saturday.

Acting chief medical officer Venessa Thornton says the organism was currently contained.

"They're in isolation and we've contained a theatre for them because obviously they need ongoing operations, and [we're] upping our inspection control processes."

While it was not a concern for most patients or visiting public, the organism could have serious implications for burns patients, says Venessa.

So far, the patients were responding well to treatments.

"Obviously they're very sick and vulnerable patients at the best of times."

She says a contingency plan set up for this kind of situation was last updated in 2011.

"It's due for another update and this will certainly prompt some ongoing review of it."

However, she says the plan had worked when needed.

"We are also considering options for transferring very serious burns cases, which would normally be treated at Counties Manukau Health, to locations in Australia. This would be on a case-by-case basis."