Legally permitted residues of antibiotics in food can lead to antibiotic resistance, according to a new study from the Institute of Tropical Medicine (ITM), published in Scientific Reports.
Antibiotics are used worldwide in livestock and fish farming. As a result, small amounts can remain in food, usually within the legally permitted maximum residue limits (MRLs).
These limits are based on the acceptable daily intake (ADI): the amount of antibiotics that can be taken daily throughout a lifetime without adverse health effects. However, even these permitted amounts can be dangerous, according to the study.
Not because they are toxic to humans, but because they promote antibiotic resistance in bacteria.
Policy needed
In a clinical study, 20 healthy volunteers were given the ADI of the antibiotic ciprofloxacin (a commonly used antibiotic worldwide) every day for four weeks. A control group of 10 participants received a placebo.
The results were clear, says the Institute: the amount of antibiotics currently legally permitted in food still led to resistant bacteria in the participants. The researchers observed resistance developing in Escherichia coli (E. coli), a widespread gut bacterium.
Additionally, the gut microbiome was disrupted: some beneficial bacterial species decreased, while others increased.
"Previous research has shown that the use of antibiotics in livestock and fish farming can lead to resistant bacteria that can then be transmitted to humans," said Chris Kenyon, ITM professor and lead author of the study.
"Our research points to a more direct cause: even small traces of antibiotics in our food can cause common bacteria in our bodies to become resistant," he said. "In other words, the problem is not just originating outside us, but also within us."
The researchers warn that current food safety regulations do not sufficiently address this. They therefore advocate for a policy revision to slow the rise of resistant bacteria.
