The problems of bacteria becoming resistant to antibiotics in human medicine are well known, but now researchers have discovered bacteria living inside sharks that have also developed drug resistance.
This worrying discovery reveals that our medicines are making their way into the marine environment - probably because some people flush unused drugs down the toilet and some drugs pass undigested through our bodies and into sewage water that eventually ends up out at sea.
Jason Blackburn, from the University of Florida, led a large team of researchers who collected samples of bacteria living inside seven shark species, including bull sharks, lemon sharks, and nurse sharks, as well as one bony fish, called redfish.
Back in the lab they tested the bacterial cultures for resistance to a range of human antibiotics, including penicillin, chloramphenicol, and doxycycline which is widely used as an anti-malaria drug.
In each study site, including Belize, Florida, and Massachusetts in the US, the team found that fish contained bacteria that were resistant to at least one of these drugs, and in some cases the bugs survived multiple antibiotics.
As well as being bad news for the sharks - which could face nasty infections from virulent strains of bacteria - this could also pose a health risk to people too.
Around the world, sharks are arriving in increasing numbers into our dinner plates, although we don't always realise it, because they are given other names like huss, greyfish, and Italy in Vitello di Mare ('Veal of the Sea'). And that's not to mention many of the other fish that sharks themselves feed on, which might also be harbouring drug-resistant bacteria.
These findings suggest that we should pay more attention to what we flush away and how our sewage water is treated.