There is concern about an increase in the cases of a super bug that's resistant to all but one antibiotic.

Dr Joshua Freeman is among a group of microbiologists whose article on CPE appears in the latest New Zealand Medical Journal.

He told Larry Williams there were a couple of cases of it in 2009 in New Zealand, but that shot up to 46 cases last year.

"Now fortunately, a lot of these were just carriers and weren't causing infection, but that can all change quite rapidly."

He said hospital patients need to be ring-fenced and protected.

"And identify carriers, not only to prevent spread, but so we can put in place special measures to prevent infections in those patients and protect them."

Dr Freeman said CPE is only treatable with a drug that went out of use in the 1970s, because of concerns about its toxicity.

However, he said resistance to even that drug is already quickly developing.

LISTEN ABOVE AS DR JOSHUA FREEMAN SPEAKS WITH LARRY WILLIAMS