A global study has compared levels of antimicrobial-resistant bacteria in sewage samples from around the world, and the findings suggest New Zealand is among the least-exposed countries.

But a prominent microbiologist cautioned the study couldn't give the full picture of New Zealand's vulnerability to the growing health crisis, considering it a "snapshot in time".

Already, an estimated 700,000-plus people worldwide die each year because of drug-resistant infections.

But the toll could be much more devastating when even today's easily-treatable diseases were found harder to combat.

University of Otago geneticist Professor Neil Gemmell, who helped collect the Dunedin samples, said he was "moderately surprised" at how the results compared globally.

"As the team concludes, we clearly live in a relatively sanitary environment, at least from a public health perspective."

However he said it's a concerning study. 

"What we do know is that we have got a substantial level of anti-microbial resistance already in the microbial population and that resistance is only going to increase as the use of antibiotics continues."

He said while this issue isn't new, we clearly aren't doing enough about it.

Gemmell said, unfortunately, it's more complicated than just prescribing fewer antibiotics.

The global study compared levels of antibiotic resistant bacteria in sewage samples from around the world, including Dunedin.

It found New Zealand among the least-exposed countries.

However Microbiologist Dr Siouxsie Wiles told Kate Hawkesby the study isn't conclusive as it was was voluntary and done three years ago.

She says to find out what's going on there needs to be a sample sewage in multiple places across the country.