Occurrence of virulence determinants, antibiotic resistance in Swedish Enterococcus faecium blood-culture isolates during a six-year period

Abstract number: 1733_443

Billström H., Sullivan Å., Lund B.

Background: Recently the isolation ratio between E. faecalis and E. faecium causing infections has shifted from 10:1 to 3:1. Suggested explanation for this has been the increasing antibiotic resistance in E. faecium. However, changes in virulence cannot be excluded. Evidences are now emerging indicating a nosocomial origin of these infections.

Objectives: To detect the presence of virulence determinants in E. faecium infectious isolates and determine changes in frequencies over time. Furthermore, to investigate the levels of antibiotic resistance towards clinically relevant antibiotics and possible genetic relationships between isolates with suspected clonality.

Methods: A total of 278 strains E. faecium isolated from bacteraemia patients during year 2000 to 2006 at the Karolinska University Hospital, Huddinge were used. All isolates were screened for the seven virulence genes, aggregation substance (asa1), cytolysin (cylA), collagen binding protein (ace), E. faecalis endocarditis antigen (efafm), enterococcal surface protein (espfm), gelatinase (gelE), and hyaluronidase (hylfm), using PCR. Minimal inhibitory concentrations were determined towards ampicillin, ciprofloxacin, daptomycin, gentamicin, linezolid and vancomycin using agar dilution. PFGE was used to detection possible identical clones.

Results: A total of 54.3% of the isolates was esp-positive. In 14 of the isolates, hyl was found. 2% of the isolates harboured one or more of ace, asa1, efaAfm and gelE. None of the isolates were cytolysin positive. Ampicillin, ciprofloxacin and imipenem resistance were high, 76%, 90% and 80% respectively, while low frequencies were found for vancomycin (4.7%) and gentamicin (1.8%). Resistance towards linezolid and daptomycin was not found.

Discussion: During the course of this 6-year study, the levels of antibiotic resistance seem to be stable. The occurrence of espfm and hylfm also appear to be constant. The more rare virulence determinants, exclusively found during the last two study years, might indicate that an increase is occurring. The high frequency of espfm and antibiotic resistance suggests that these factors are of importance for infection development. However, if this is the case further unknown traits probably exist since a significant part of the isolates lacks all the investigated determinants.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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