Cutting the number of antibiotics prescriptions led to a fall in superbug cases, a health board has said.
Betsi Cadwaladr health board's primary care prescription rate for antibiotics fell by 12.6% from 2017-18 to 2018-19.
Bosses claim it has resulted in a fall in cases of C. difficile, which commonly affects people who have recently been treated with antibiotics.
England's health secretary has said drug-resistant superbugs were as big a threat as climate change.
The health board said there were 166 cases of patients developing C. difficile in 2018-19, compared with 271 in 2017-18.
Betsi Cadwaladr said its reduction in antibiotic prescriptions - more than double the Wales target of 5% - also saved it £185,000 in the past year.
There is concern overuse of antibiotics has led to superbugs developing resistance, reducing the effectiveness of some drugs and making it more difficult to treat infections.
It has done so through cutting prescriptions of antibiotics in primary health care including GP surgeries and pharmacies, which accounts for more than 80% of prescriptions in north Wales.
Pauline Roberts, Betsi Cadwaladr's primary care pharmacist, said: "Everyone understands we have a problem nationally with the overuse of antibiotics, but it's hard to change without the tools to improve the way we deliver care.
"We've tried to work with GP practices to give them resources to support this work, and supporting them by educating patients that antibiotics don't work against viruses."
The health board has also been conducting a pilot scheme, along with Cwm Taf Morgannwg health board, where pharmacists test people with sore throats.
If the infection proves to be viral - which antibiotics will not treat - the drug is not prescribed.
In some surgeries, such as Ty Doctor in Nefyn, Gwynedd, a pin prick of blood allows a machine to measure inflammatory markers to see if the results warrant antibiotics.
Dr Eilir Hughes said it was helping prove to patients antibiotics were not always necessary, and people were starting to understand the problem.
Other health boards have reported similar cuts, including a 10% reduction in antimicrobials dispensed by Cardiff and Vale health board in the 12 months to March 2019, compared to 2016-17.
Public Health Wales said health boards had made "excellent progress", and complete results would be released in the autumn.
"Antimicrobial resistance continues to be a serious public health concern requiring co-ordinated action across healthcare agencies and governments," said PHW's Dr Eleri Davies.
Antibiotic prescription reductions by GPs in 2017-18
- Betsi Cadwaladr: 5.9%
- Powys: 1.9%
- Hywel Dda: 1.8%
- Abertawe Bro Morgannwg (now Swansea Bay): 1.1%
- Aneurin Bevan: 1.1%
- Cardiff and Vale: 1.1%
- Cwm Taf (now Cwm Taf Morgannwg): 0.8%
Source: Public Health Wales