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.

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One recent landmark report estimated that, without urgent action, antimicrobial resistance would kill 10 million people a year by 2050 - more than will die from cancer.

The new study, just published in the major scientific journal Nature Communications, looked at levels and types of antimicrobial-resistant bacteria in healthy populations around the globe.

Using metagenomic approaches, the researchers mapped out DNA material in sewage collected from 74 cities – including Dunedin – in 60 countries.

They found those from North America, Western Europe, Australia and New Zealand generally had the lowest levels of antimicrobial resistance, while Asia, Africa and South America have the highest levels.

Brazil, India and Vietnam have the greatest diversity in resistance genes, while Australia's and New Zealand's samples returned the lowest.

According to the researchers, the use of antibiotics only explained a minor part of the occurrence of antimicrobial resistance in the various countries.

Therefore, they searched for other factors that could be either drivers for or indicators of the occurrence of resistant bacteria.

This map shows predicted abundance of antimicrobial from light blue (low abundance) to dark blue (high abundance). Source / Technical University of Denmark
This map shows predicted abundance of antimicrobial from light blue (low abundance) to dark blue (high abundance). Source / Technical University of Denmark

In the study, they used several comprehensive data sets from the World Bank, that measured the countries' health status and stage of development.

Most of the variables were found to be linked to the sanitary conditions in the country, along with the population's general state of health.

"In the fight against antimicrobial resistance, our findings suggest that it would be a very effective strategy if concerted efforts were made to improve sanitary conditions in countries with high levels of antimicrobial resistance," said study leader Professor Frank Aarestrup, of the Technical University of Denmark.

Using the same data from the World Bank, the researchers also predicted the levels of antimicrobial resistance in 259 countries.

According to their estimates, the Netherlands, New Zealand and Sweden had the lowest levels of resistance, whereas Tanzania, Vietnam and Nigeria had the highest levels.

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."

University of Auckland microbiologist Associate Professor Siouxsie Wiles pointed out the small number of samples might not be representative of the countries they were collected from.

"To find out what's going on in New Zealand we need to sample multiple places and it needs to be more than just a snapshot in time," Associate Professor Siouxsie Wiles says. Photo / File

"So I don't think we can make any conclusions from a study that involved just one sample from Dunedin taken two years ago."

Wiles, the author of the book Antibiotic Resistance: The End of Modern Medicine?, had been awaiting the results and was pleased to see that the approach worked.

"We can use sewage to try to monitor what antibiotic resistance is circulating, potentially in healthy people, without having to swab lots of healthy people," she said.

"Clearly, to find out what's going on in New Zealand, we need to sample multiple places and it needs to be more than just a snapshot in time.

"Some colleagues and I have been trying to get funding to trial such a system in Auckland, but we've not been successful yet."

While New Zealand's rate of antimicrobial resistance was known to be comparatively low, especially compared with neighbouring regions, there had been a rise in resistance to some types of infections - all while the use of antibiotics was increasing.

Health authorities have a national action plan to tackle the threat and are running a range of initiatives, including education and surveillance programmes, putting restrictions on prescription and improving appropriate use of the drugs.