Emergence of plasmid-mediated tigecycline resistance tet(X4)gene in Enterobacterales isolated from wild animals in captivity

Background Over the past few decades,antimicrobial resistance(AMR)has emerged as a global health challenge in human and veterinary medicine.Research on AMR genes in captive wild animals has increased.However,the presence and molecular characteristics of tet(X)-carrying bacteria in these animals remain unknown.Methods Eighty-four samples were collected from captive wild animals.tet(X)variants were detected using polymerase chain reaction and the isolates were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.All isolated strains were subjected to antimicrobial susceptibility testing and whole-genome sequencing.The virulence of an Escherichia coli strain carrying enterotoxin genes was assessed using a Galleria mellonella larval model.Results We isolated two tet(X4)-positive E.coli strains and one tet(X4)-positive Raoultella ornithinolytica strain.Antimicrobial susceptibility tests revealed that all three tet(X4)-carrying bacteria were sensitive to the 13 tested antimicrobial agents,but exhibited resistance to tigecycline.Notably,one tet(X4)-carrying E.coli strain producing an enterotoxin had a toxic effect on G.mellonella larvae.Whole-genome sequencing analysis showed that the two tet(X4)-carrying E.coli strains had more than 95%similarity to tet(X4)-containing E.coli strains isolated from pigs and humans in China.Conclusion The genetic environment of tet(X4)closely resembled that of the plasmid described in previous studies.Our study identified tet(X4)-positive strains in wildlife and provided valuable epidemiological data for monitoring drug resistance.The identification of enterotoxin-producing E.coli strains also highlights the potential risks posed by virulence genes.

Emergence of plasmid-mediated tigecycline resistance tet(X4)gene in Enterobacterales isolated from wild animals in captivity

Background:Over the past few decades,antimicrobial resistance(AMR)has emerged as a global health challenge in human and veterinary medicine.Research on AMR genes in captive wild animals has increased.However,the presence and molecular characteristics of tet(X)-carrying bacteria in these animals remain unknown.Methods:Eighty-four samples were collected from captive wild animals.tet(X)variants were detected using polymerase chain reaction and the isolates were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.All isolated strains were subjected to antimicrobial susceptibility testing and wholegenome sequencing.The virulence of an Escherichia coli strain carrying enterotoxin genes was assessed using a Galleria mellonella larval model.Results:We isolated two tet(X4)-positive E.coli strains and one tet(X4)-positive Raoultella ornithinolytica strain.Antimicrobial susceptibility tests revealed that all three tet(X4)-carrying bacteria were sensitive to the 13 tested antimicrobial agents,but exhibited resistance to tigecycline.Notably,one tet(X4)-carrying E.coli strain producing an enterotoxin had a toxic effect on G.mellonella larvae.Whole-genome sequencing analysis showed that the two tet(X4)-carrying E.coli strains had more than 95%similarity to tet(X4)-containing E.coli strains isolated from pigs and humans in China.Conclusion:The genetic environment of tet(X4)closely resembled that of the plasmid described in previous studies.Our study identified tet(X4)-positive strains in wildlife and provided valuable epidemiological data for monitoring drug resistance.The identification of enterotoxin-producing E.coli strains also highlights the potential risks posed by virulence genes.

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