For decades we鈥檝e known that bacteria can evolve resistance to antibiotics but now it looks like other types of common drugs, including ibuprofen, may also help drive antimicrobial resistance.
Bacteria are able to swap genetic material with completely different strains, a process that has enabled drug resistance genes to rapidly spread to many types of microbe. Now a team in Australia has found that five commonly-used non-antibiotic drugs appear to encourage gene swapping between bacteria.
The study looked at six drugs: ibuprofen and two other anti-inflammatories 鈥� naproxen and diclofenac 鈥� as well as the lipid-lowering drug gemfibrozil, the beta-blocker propranolol, and iopromide, which is used to produce better X-ray images.
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Each of the drugs was mixed in a vial containing two types of bacteria, one of which was resistant to three types of antibiotic, while the other was resistant to a different, fourth type of antibiotic.
After eight hours of incubation, the mixtures were tested to see if they contained any bacteria that could now resist all four of the antibiotic drugs.
Control mixtures, which weren鈥檛 exposed to any drug, didn鈥檛 produce any bacteria capable of resisting all four antibiotics. Neither did the bacteria exposed to iopromide.
Cellular changes
But quadruple-resistant bacteria did arise after exposure to ibuprofen, naproxen, diclofenac, gemfibrozil or propranolol. This occurred even when ibuprofen, naproxen and gemfibrozil were at extremely low concentrations 鈥� as little as 0.005 milligrams per litre.
DNA analysis confirmed that resistance genes had indeed swapped between the different strains of bacteria.
The team found that exposure to these five drugs was linked to cellular changes that may have made it easier for the bacteria to release and absorb each other鈥檚 DNA.
The study shows that we have much more to learn about what drives the transfer of resistance genes, says Adam Roberts of the Liverpool School of Tropical Medicine, UK.
He says it challenges traditional thinking on how to tackle the problem of antibiotic resistance. 鈥淩educe antibiotics and that will reduce selection pressure and resistance will disappear 鈥� that鈥檚 just not true,鈥� he says.
Katherine Duncan at the University of Strathclyde, UK, says the low concentrations of drugs used in the study mirror the extent to which medicines like ibuprofen may be present in the wider environment, for example in sewage. However, she notes that, outside of laboratory conditions, many other chemicals may accelerate or decelerate the gene transfer process.
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