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Antimicrob Agents Chemother. 1996 Feb;40(2):354-7.

Modification of penicillin-binding protein 5 associated with high-level ampicillin resistance in Enterococcus faecium.

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1
Istituto di Microbiologia, Università degli Studi di Verona, Italy.

Abstract

High-level ampicillin resistance in Enterococcus faecium has been shown to be associated with the synthesis of a modified penicillin-binding protein 5 (PBP 5) which had apparently lost its penicillin-binding capability (R. Fontana, M. Aldegheri, M. Ligozzi, H. Lopez, A. Sucari, and G. Satta. Antimicrob. Agents Chemother. 38:1980-1983, 1994). The pbp5 gene of the highly resistant strain E. faecium 9439 was cloned and sequenced. The deduced amino acid sequence showed 77 and 54% homologies with the PBPs 5 of Enterococcus hirae and Enterococcus faecalis, respectively. A gene fragment coding for the C-terminal part of PBP 5 containing the penicillin-binding domain was also cloned from several E. faecium strains with different levels of ampicillin resistance. Sequence comparison revealed a few point mutations, some of which resulted in amino acid substitutions between SDN and KTG motifs in PBPs 5 of highly resistant strains. One of these converted a polar residue (the T residue at position 562 or 574) of PBP 5 produced by susceptible and moderately resistant strains into a nonpolar one (A or I). This alteration could be responsible for the altered phenotype of PBP 5 in highly resistant strains.

PMID:
8834879
PMCID:
PMC163115
[Indexed for MEDLINE]
Free PMC Article
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