New research from the University of Queensland (UQ) has found that a common antidepressant could be contributing to antibiotic resistance and the creation of "superbug" strains of pathogenic bacteria.
Australia currently has the second-highest rate of antidepressant prescriptions in the world, with 104 daily antidepressant prescriptions per 1000 people.
The study focused on fluoxetine, a selective serotonin reuptake inhibitor (SSRI), which is the active ingredient in antidepressant brands such as Prozac.
Fluoxetine was developed in the 1970s and is used to treat depression, obsessive-compulsive disorder, anxiety and eating disorders.
It is one of the most popular SSRIs and Prozac is one of the only SSRI's currently approved for use in children over 8 years-old.
The research team from UQ decided to test the drug after discovering earlier this year in another study that a common ingredient in toothpaste known as triclosan could directly increase antibiotic resistance in waterways.
Up to 11% of fluoxetine doses that a patient consumes remain unchanged and is introduced into waterways by urine. The researchers hypothesised that this could have an effect on bacteria in both the environment and in the human body.
The researchers looked at the effects of fluoxetine on E.coli K12 (a generally harmless strain of E.coli that is typically found in the human gut and exists in waterways) and found that the drug increases the bacteria's resistance to antibacterial drugs.
The bacteria showed an increased rate in genetic mutations in their efflux pumps (transporters in cells that expel toxic substances) after 30 days of exposure to fluoxemine, allowing the cells to expel antibiotics more easily.
Doctor Jianhua Guo from UQ's Advanced Water Management Centre and lead author of the study, told BuzzFeed News that they chose to study this strain of E.coli because it is known to be sensitive to antibiotics, and that they were surprised to find a significant reduction in that sensitivity after exposure to the antidepressant.
However Guo says this is a preliminary study and the concentrations used were extremely high compared to those seen in the environment.
"This is a fundamental study...fluoxetine is not an antibiotic, so we just wanted to assess if it's a potential risk or not," said Guo. "We didn't do an animal experiment or a human experiment to confirm it. In the future we have to do an animal experiment or an in situ experiment to confirm it."
Guo says people should continue taking their prescription medication and that this research is merely an early warning sign for the pharmaceutical industry.
While this effect has only been observed in the single strain of E.coli with one particular antidepressant drug, the researchers believe that this is the first indication that the effects of fluoxetine and other antidepressants on bacteria in the gut need to be investigated.
Approximately 700,000 deaths per year worldwide can be attributed to antimicrobial-resistant infections. That figure is predicted by the UK Antimicrobial Resistance review to reach 10 million by 2050.