Canterbury District Health Board (CDHB) said that three people tested positive as potential carriers of Carbapenem-resistant Enterobacteriaceae (CRE).
CRE are a family of germs that are difficult to treat because they have high levels of resistance to antibiotics. Thirty people tested positive for CRE in the country between 2009 and 2014.
However, Auckland University Associate Professor Mark Thomas said the problem would become more difficult for the health sector to manage in the future.
The professor said that though the three Canterbury patients may never have any issue with the germ, there was potential for CRE carriers to develop life-threatening infections and the numbers of CRE carriers would increase.
"They are the beginning of what will inevitably be a lot more of these patients and at the moment we don't have safe, cheap, convenient antibiotics to treat those sorts of organisms with. So if a patient has an infection of the kidney or an abcess in the abdomen or an infection of their gall bladder or bile duct due to CRE, then doctors all around the world have great difficulty in treating these infections," Thomas added.
The presence of CRE was detected as part of routine screening while the patients were in hospital.