Antibacterial toothpastes, mouthwashes, soaps and handwashes are fuelling antibiotic resistant superbugs, according to new research.
Rather than killing dangerous bacteria, Triclosan, is actually making them stronger – and more capable of surviving treatment.
The chemical added to a range of household products for its “antibacterial” property prevents infections responding to the life saving drugs.
The US Food and Drug Administration has already banned its use in hand washes over safety fears.
Triclosan is also commonly used in cosmetics, clothing, baby toys and even credit cards with the intention of protecting health.
Professor Petra Levin, of Washington University, St Louis, said: “In order to effectively kill bacterial cells, triclosan is added to products at high concentrations.”
But the study published in Antimicrobial Agents & Chemotherapy found it inadvertently enables them to tolerate normally lethal doses of antibiotics.
These include drugs widely used to treat urinary tract infections (UTIs) – one of the most common health problems among women.
What is more, triclosan is very stable.
Prof Levin said: “It lingers in the body and in the environment for a long time.”
Experiments on mice showed the extent to which exposure limits the body’s ability to respond to antibiotic treatment for UTIs – and sheds fresh light on the mechanism.
Lab member Dr Corey Westfall treated bacterial cells with bactericidal antibiotics and tracked their ability to survive over time.
In one group, the bacteria were exposed to triclosan prior to being given the antibiotic. In the other group, they were not.
Prof Levin said: “Triclosan increased the number of surviving bacterial cells substantially.
“Normally, one in a million cells survive antibiotics, and a functioning immune system can control them.
“But triclosan was shifting the number of cells.
“Instead of only one in a million bacteria surviving, one in 10 organisms survived after 20 hours. Now, the immune system is overwhelmed.”
Triclosan exposure allowed the bacteria to escape death by antibiotics. And the protective property was not limited to any single family.
In fact, multiple antibiotics that are considered unique in how they kill cells were less effective at killing bacteria exposed to triclosan.
Dr Westfall said: “Triclosan increased tolerance to a wide breadth of antibiotics.
“Ciprofloxacin (also known as Cipro) was the most interesting one to us because it is a fluoroquinolone that interferes with DNA replication and is the most common antibiotic used to treat UTIs.”
They are mainly caused by E.coli (Escherichia coli). Antibiotics such as Cipro are commonly used to kill the bacteria and treat the infection.
About three in four adults in the US have detectable levels of triclosan in their urine. These are high enough to prevent E. coli from growing in around one in ten.
The experiments showed antibiotics were less effective at treating UTIs when triclosan is around.
This was because it worked with a cell growth inhibitor, a small molecule nicknamed ppGpp, to render cells less sensitive to antibiotics.
Prof Levin said clinical studies would be required to definitely prove triclosan is interfering with antibiotic treatments in humans.
She added: “My hope is this study will serve as a warning that will help us rethink the importance of anti-microbials in consumer products.”
By Mark Waghorn & Joe Mellor