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Antibiotic Resistance in Wallabies

By Stephen Luntz

Brushtail rock wallabies bred in captivity carry antibiotic-resistant bacteria in their guts while their wild counterparts do not, a study in PLOS One has revealed.

Since wild wallabies will seldom be treated with antibiotics, the danger to the population is small if the resistance spreads when the wallabies are released. However, the finding indicates the extent to which antibiotic resistance could migrate and transform.

Brushtail rock wallabies are endangered in NSW and considered near-endangered nationally, leading to a successful captive breeding program. However, Dr Michelle Power of Macquarie University’s School of Biological Sciences found that 48% of faecal samples from wallabies in the program showed evidence of bacteria resistant to common antibiotics. No samples from their wild cousins carried the same traits.

“How these genes made their way into the wallaby microbes is unknown, but it seems likely that water or feed may have acted as a conduit for bacteria carrying these genes,” Power and her colleagues reported.

Once away from human influence and the selection pressures of exposure to antibiotics it remains to be seen whether the resistant strains will be transferred to the offspring of captive-bred wallabies released or to wild wallabies. Power says her team is keen to investigate whether this happens as releases occur.

Evidence of the easy shift from humans or livestock to wallabies provides a warning about how easily resistant genes can shift from one species of bacteria to another. Power says this creates the danger that crossed bacterial strains could one day be transferred back to humans from animals carrying resistant genes.

“I’m not sure we can stop this happening,” says Power. “However, we need to think about monitoring in wild populations to minimise risks.”