The emergence of inactivation enzyme-encoding genes
tet(X),
blaEBR, and
estT challenges the effectiveness of tetracyclines, β-lactams, and macrolides. This study aims to explore the concurrence and polymorphism of their variants in
Empedobacter sp. strains from food-producing animals and surrounding environments.
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The emergence of inactivation enzyme-encoding genes
tet(X),
blaEBR, and
estT challenges the effectiveness of tetracyclines, β-lactams, and macrolides. This study aims to explore the concurrence and polymorphism of their variants in
Empedobacter sp. strains from food-producing animals and surrounding environments. A total of eight
tet(X) variants, seven
blaEBR variants, and seven
estT variants were detected in
tet(X)-positive
Empedobacter sp. strains (6.7%) from chickens, sewage, and soil, including 31
Empedobacter stercoris and 6 novel species of Taxon 1. All of them were resistant to tigecycline, tetracycline, colistin, and ciprofloxacin, and 16.2% were resistant to meropenem, florfenicol, and cefotaxime. The MIC
90 of tylosin, tilmicosin, and tildipirosin was 128 mg/L, 16 mg/L, and 8 mg/L, respectively. Cloning expression confirmed that
tet(X6) and the novel variants
tet(X23),
tet(X24),
tet(X25),
tet(X26), and
tet(X26.2) conferred high-level tigecycline resistance, while all of the others exhibited relatively low-level activities or were inactivated. The bacterial relationship was diverse, but the genetic environments of
tet(X) and
blaEBR were more conserved than
estT. An IS
CR2-mediated
tet(X6) transposition structure, homologous to those of
Acinetobacter sp.,
Proteus sp., and
Providencia sp., was also identified in Taxon 1. Therefore, the
tet(X)-positive
Empedobacter sp. strains may be ignored and pose a serious threat to food safety and public health.
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