An unusual resistance phenotype in nosocomial strains of Enterococcus species in a Greek hospital

Abstract number: 1134_01_370

Metzidie E., Pournaras S., Sofianou D.


Enterococcus faecalis is a common nosocomial agent and usually demonstrates susceptibility to ampicillin, penicillin G and amoxicillin/clavulanicate, while Enterococcus faecium is commonly resistant to the above mentioned antimicrobial agents. The aim of our study is the presentation of an unusual resistance phenotype that was recently identified in a Greek tertiary hospital among A. faecalis and E. faecium, exhibiting resistance to penicillin and susceptibility to ampicillin and amoxicillin/clavulanate.


A total of 35 non-repetitive enterococcal strains were collected from various hospital infection samples. Identification and susceptibility testing were performed by using the Vitek 2 automated system (Biomerieux, Marcy l’ Etoile, France). The MICs for penicillin G, ampicillin and amoxicillin/clavulanic acid were determined using E-test. The production of beta-lactamase was evaluated using the cefinase test.


Among 35 isolates, 33 were identified as E. faecalis and 2 as E. faecium. All isolates were susceptible to ampicillin and amoxicillin/clavulanic acid with MIC ranging from 0.38 to 1.50 mg/L respectively but they were resistant to penicillin (MIC > 32 mg/L). Using the cefinase test they were found to be negative for beta-lactamase production. PFGE analysis revealed various unrelated clonal patterns.


A spread of this unusual resistance phenotype would affect the usefulness of penicillin that generally retains activity against E. faecalis. The aetiology of this phenotype is an object of study.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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