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Enterococcus casseliflavus HZ95 is an enterococcus with high-level resistance to aminoglycosides. Nine genes responsible for high-level aminoglycoside resistance, including aac(6′)-Ie-aph(2″)-Ia, aph(2″)-Ib, aph(2″)-Ic, aph(2″)-Id, aph(3′)-IIIa, aac(6′)-Ii, ant(3′)-Ia, ant(4′)-Ia and ant(6′)-Ia, were not detected in HZ95. An 8 kb fragment from unconjugative plasmids of HZ95 was cloned, and expressed gentamicin resistance in Escherichia coli DH5α. The genetic structures (∼8 kb DNA fragment) containing these aminoglycoside-modifying enzyme genes in Ent. casseliflavus HZ95 were determined. The deduced amino acid sequence of the novel aph(2″) allele, aph(2″)-Ie, had 93.7 % amino acid identity with APH(2″)-Id. The aph(2″)-Ie gene was bracketed upstream by an insertion sequence (IS)Ecp1-like element and downstream by a streptomycin adenylyltransferase gene (str). The streptomycin adenylyltransferase encoded by the str gene had 80.3 % amino acid identity with the protein encoded by aadE. The plasmid of ∼16 kb could hybridize with a PCR-generated aph(2″)-Ie intragenic probe. The ISEcp1-like element had 91 % identity with ISEcp1. ISEcp1, which commonly acts as a key factor in the dissemination of CTX-M-type β-lactamase genes in Gram-negative bacteria, has not been reported in Enterococcus.
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