A widely prescribed antidepressant could be causing antibiotic resistance and contributing to the creation of superbugs, Queensland researchers say.

The study, led by Dr Jianhua Guo from the University of Queensland's Advanced Water Management Centre, looked at the prescription drug fluoxetine which is a common ingredient in antidepressants such as Prozac and Lovan.

Antimicrobial resistance occurs when microorganisms such as bacteria, fungi, viruses and parasites change when exposed to some drugs such as antibiotics and antifungals, according to the World Health Organisation (WHO).

WHO says antibiotic resistance occurs naturally but is spreading globally and making it difficult to treat common infections because of misuse of antibiotics in humans and animals.

Fluoxetine is not an antibiotic, but a selective serotonin reuptake inhibitor (SSRI) drug.

Doctors often prescribe it to patients suffering from depression, obsessive-compulsive disorder, panic attacks, anxiety and some eating disorders.

Dr Jianhua Guo (R) and his colleague Dr Min Jim(L) have found certain bacteria exposed to fluoxetine for weeks or months mutated and became resistant to multiple antibiotics. ( ABC News: Gail Burke )

Overuse of antibiotics a 'major factor'

Key facts about AMR Antimicrobial resistance (AMR) threatens the effective prevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, viruses and fungi.

Antimicrobial resistance (AMR) threatens the effective prevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, viruses and fungi. AMR is an increasingly serious threat to global public health that requires action across all government sectors and society.

AMR is an increasingly serious threat to global public health that requires action across all government sectors and society. Without effective antibiotics, the success of major surgery and cancer chemotherapy would be compromised.

Without effective antibiotics, the success of major surgery and cancer chemotherapy would be compromised. The cost of health care for patients with resistant infections is higher than care for patients with non-resistant infections due to longer duration of illness, additional tests and use of more expensive drugs.

The cost of health care for patients with resistant infections is higher than care for patients with non-resistant infections due to longer duration of illness, additional tests and use of more expensive drugs. In 2016, 490,000 people developed multi-drug resistant TB globally, and drug resistance is starting to complicate the fight against HIV and malaria. Source: WHO

Dr Guo said his laboratory tests found certain bacteria exposed to fluoxetine for weeks or months mutated and became resistant to multiple antibiotics.

"Our common understanding is that overuse and misuse of antibiotics is generally considered the major factor contributing to the creation of 'superbugs'," he said.

"However, our study could change or advance our understanding, because non-antibiotic pharmaceuticals such as fluoxetine can directly induce antibiotic resistance.

"The higher the exposure concentration was, the faster the mutation frequency increased with time."

Dr Guo has previously worked on a study that found triclosan — a common ingredient in toothpaste and hand wash — could directly induce antibiotic resistance.

He said other studies on fluoxetine had found up to 11 per cent of the dose a patient took remained unchanged and made its way through the sewage system via urine.

He said it was important that scientists looked beyond the role antibiotics played in the rise of superbugs considering the wide use of fluoxetine.

"Our findings are a wake-up call to start re-evaluating the potential antibiotic-like roles induced by non-antibiotic drugs," Dr Guo said.

"Further work is required to investigate effects of fluoxetine on antibiotic resistome in human gut microbiota."

Lab results may not mirror real life

Dr Guo said scientists needed to look beyond just the role antibiotics played in the rise of superbugs. ( Supplied: University of Queensland )

The chair of the Psychiatrists Group at the Australian Medical Association (AMA), Professor Steve Kisely, said while the findings were intriguing, they should be kept in context.

"What happens in the lab can be very different to what happens in real life," Professor Kisely said.

"I'd be concerned that people will get alarmed … we need further research before we make any clear-cut recommendations.

"It's a signal but there are signals going in opposite directions.

"Other studies have shown fluoxetine can enhance antibiotic, anti-malarial, and antifungal efficacy."

Professor Kisely said people who had been prescribed the drug should remember there had not been any clinical tests on the link between the antidepressant and antibiotic resistance.

"Particularly as the findings are in conflict with other studies," he said.

"The beneficial effects of fluoxetine are well established, and people should not stop taking it on the basis of this study."

Research shows about 700,000 people a year die from antimicrobial-resistant infections and that number could grow to 10 million people by 2050.

