Background
Patients are often screened with surveillance cultures to discern transmissions vs
transformation of an isolate to vancomycin-resistant Enterococcus faecium. To determine the amount of time between which isolates could be considered genetically
similar by pulsed-field gel electrophoresis, isolate change over time within single
patients was studied.
Methods
A minimum of 4 isolates per patient, separated by at least 2 months, were collected
from previously frozen stores. Visual comparison of banding patterns was conducted,
and percent relatedness was calculated.
Results
Twenty-eight isolates from 6 patients were studied. No isolate differed by more than
3 bands before 150 days, and the average percent difference per band was 3.7%. The
isolates diverged genetically as a linear function of number of bands over time (good
model fit intrapatient r2 = 0.42; poor model fit interpatient r2 = 0.0062).
Conclusion
Trajectory of genetic variation appears to be isolate/patient specific; however, commonalities
exist and tested isolates were relatively stable out to 150 days.
Key Words
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Article info
Publication history
Published online: October 26, 2012
Footnotes
This study was supported in part by a Midwestern University Chicago College of Pharmacy Faculty Research Stimulation Grant.
Conflicts of interest: None to report.
Identification
Copyright
© 2013 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.
