BACTERIA that are resistant to antibiotics are becoming disturbingly common in people. More worrying still is that the genes which confer this resistance are also showing up in bacteria found in other animals. When resistant bacteria hop between species, that can increase the rate of evolution and, over time (through the sharing of independently evolved traits) turn a mildly resistant bug that is merely a nuisance into a serious threat.
This has left researchers wondering how resistant bacteria get into animals in the first place. One possibility is that genes for antibiotic-resistance circulate naturally in wild populations. Many antibiotics are, after all, derived from the natural defence mechanisms of other micro-organisms, so it is not unreasonable to think that antiantibiotics, too, are widespread in nature. Another possibility is that human antibiotic use has promoted the circulation of resistance genes to other species.
Until recently, most of the studies that have looked at bacteria in such species have concentrated on domestic animals. But a team of biologists led by Trine Glad and Monica Sundset at the University of Tromso, in Norway, has now looked properly in the wild. In fact, they have gone just about as wild as it is possible to get, examining polar bears on the Arctic archipelago of Svalbard. They chose these bears because they neither interact with people nor prey on animals that spend any significant amount of time near human settlements. The team theorised that if the circulation of antibiotic-resistance genes was a natural phenomenon, they would find these genes even in this isolated population. If it was not natural, they reckoned the bears would carry few, if any, bacteria with such resistance.