Tetracycline Resistance Genes in Wild Birds from a Wildlife Recovery Centre in Central Italy

Simple Summary Antimicrobial resistance (AMR) is recognised as an urgent global threat, both in human and in veterinary medicine. In recent years, increasing interest has turned to wild animals in order to evaluate their role as additional sources of antimicrobial resistance. Resistant bacteria may be cycling through wildlife and back into the ecosystem, then wildlife populations may act as sentinels for AMR in the environment. In this study, an epidemiological investigation of the spread of tetracycline resistance (tet) genes in wild birds was performed using a culture-independent approach. Positivity for one or more tet genes was found in 114 (45%) of 254 free-living birds tested. In view of the growing anthropogenic pressure, the spread of antimicrobial resistance in wildlife and the implications for resistance control strategies will have to be considered carefully. Wild animals are less likely to be exposed directly to clinical antimicrobial agents than domestic animals or humans, but they can acquire antimicrobial-resistant bacteria through contact with humans, animals, and the environment. In the present study, 254 dead free-living birds belonging to 23 bird species were examined by PCR for the presence of tetracycline resistance (tet) genes. A fragment of the spleen was collected from each bird carcass. A portion of the intestine was also taken from 73 of the 254 carcasses. Extracted DNA was subjected to PCR amplification targeting the tet(L), tet(M), and tet(X) genes. In total, 114 (45%) of the 254 birds sampled belonging to 17 (74%) of the 23 bird species tested were positive for one or more tet genes. The tet(M) gene showed a higher frequency than the other tested genes, both in the spleen and in the intestine samples. These results confirm the potential role of wild birds as reservoirs, dispersers, or bioindicators of antimicrobial resistance in the environment.

Automated summary

In this study, a culture-independent approach was used to investigate the spread of tetracycline resistance genes in wild birds, with 114 out of 254 birds tested showing positivity for one or more genes. Wild animals, including birds, can act as reservoirs, dispersers, or bioindicators of antimicrobial resistance in the environment. The implications of antimicrobial resistance in wildlife and the need for careful consideration of resistance control strategies are highlighted.