The prevalence of antimicrobial resistant bacteria in wildlife in Lithuania

The resistance of bacteria to antimicrobials becomes a rising health problem. The importance of wild animals as potential vectors of diseases has received recent renewed empirical interest, especially regarding human health. Under common conditions, wild animals do not have direct contact with anthropogenic elements of the animate and inanimate nature, however, in the samples of bacteria isolated from the wild nature, changes in sensitivity of antimicrobial substances are visible. The aim of this study was to investigate the prevalence of resistant Escherichia coli, Staphyloccocus spp. and Salmonella enterica in different wild animal species (birds, deers, reptiles, European bisons) in Lithuania as well as to identify genes encoding antimicrobial resistance. During the study, a total 560 wild animal samples were investigated: 415 from birds, 69 from deer, 54 from bisons and 22 from reptiles. The permissions for the investigations were obtained from the Environmental Protection Agency under the Ministry of Environment of the Republic of Lithuania. Antimicrobial susceptibility testing was performed using the disk diffusion method according to Kirby-Bauer. The results were interpreted according to the European Committee on Antimicrobial Susceptibility Testing licensed by EUCAST clinical breakpoints and Clinical and Laboratory Standards Institute (CLSI) guidelines. The resistant isolates were tested by polymerase chain reaction (PCR) for the detection of the genes encoding resistance. Staphylococcus spp. isolates were recovered from birds (the prevalence was 57.1%) and deer (15.9 %). E. coli isolates were obtained from birds (45.3 %), deer (58 %) and European bisons (66.6 %). The results demonstrated that only reptiles were carriers of Salmonella enterica (18.2 %). The results of PCR confirmed the presence of the genes encoding resistance to beta-lactams; aminoglycosides, macrolides, tetracycline, amphenicols, trimethoprim and sulphonamides. E. coli isolated from the European herring gulls (Larus argentatus) harboured mcr-1 gene encoding resistance to colistin. This study demonstrated that wild animals are carriers of antibiotic resistant bacteria. These bacteria are often resistant to different classes of antimicrobials including those that are critically important for humans – aminoglycosides, aminopenicillins and fluoroquinolones. Moreover, microbiota of wild animals share the same antimicrobial resistance genes that are important in acquired resistance of bacteria prevalent in humans and domestic animals. Control measures for disposal of antibiotics should be tightened as residues of antimicrobials and resistant bacteria from the environment can be passed into wild animals and later transferred into environment, other animals and humans.