Antibiotic resistance has been identified as one of the world’s most pressing issues. The spread of antibiotic resistance is commonly attributed to overuse of antibiotics in both human health and animal production. However, we are seeing increasing reports of antibiotic resistance in diverse wildlife species, and in the absence of antibiotic therapy. Antibiotic resistance in wildlife has been reported for both captive and wild populations, and proximity to humans is a significant factor associated with presence of resistance. Knowledge of the genetic basis of antibiotic resistance has shed light on the rapidity of emergence and role of antibiotic use as a selective agent. Class 1 Integrons are naturally occurring mobile genetic elements which facilitate the spread of antibiotic resistance within and between bacterial species. The class 1 integron is primarily associated with human clinical resistance in Gram negative bacteria. By determining the presence of class 1 integrons, and their associated resistance profiles, in wildlife species we are able to investigate penetration of antibiotic resistance into wildlife populations. We have been investigating threatened wildlife hosts of terrestrial and marine origin to determine carriage of antibiotic resistance determinants. In terrestrial environments we have identified class 1 integrons in captive bred rock wallabies that form the primary population of supplementation of wild populations. Similarly, we have found class 1 integrons in the Tasmanian devil insurance population. In marine vertebrates, class 1 integrons have been identified in little penguins inhabiting Sydney Harbour and in endangered Australian sea lions. Or data shows that antibiotic resistance elements are being transferred from terrestrial to marine environments. In captivity, the presence of antibiotic resistance potentially impacts efficacy of treatments for bacterial infections. In the wild, these elements provide an indicator of movement and colonization of bacterial species from human and domestic animal sources.