| 17030911 |
Chen YG, Qu TT, Yu YS, Zhou JY, Li LJ: Insertion sequence ISEcp1-like element connected with a novel aph (2'') allele [aph (2'')-Ie] conferring high-level gentamicin resistance and a novel streptomycin adenylyltransferase gene in Enterococcus. J Med Microbiol. 2006 Nov;55(Pt 11):1521-5.
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 DH5alpha. The genetic structures ( approximately 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 approximately 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 beta-lactamase genes in Gram-negative bacteria, has not been reported in Enterococcus. |
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