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Journal of Clinical Microbiology, Sep 1997, 2325-2330, Vol 35, No. 9
S Satake, N Clark, D Rimland, FS Nolte and FC Tenover
Surveillance cultures for vancomycin-resistant enterococci (VRE) are
time-consuming and expensive for the laboratory to perform. Therefore, we
investigated the use of PCR as an alternative method of detecting and
identifying VRE directly in fecal samples. PCR primers directed to vanA,
vanB, vanC1, vanC2, and enterococcal ligase genes were used to detect and
identify VRE in fecal material obtained by rectal or perirectal swabbing.
Although PCR-inhibitory substances were present in DNA prepared directly
from the swabs, the inhibitory substances could be reduced by processing
the nucleic acid with two commercially available DNA preparation columns.
Fecal material from 333 swabs was cultured on several selective agar media
before and after broth enrichment. DNA was extracted from the fecal
material and was analyzed by PCR. By using all four primer sets, only 59
(67.8%) of the samples were positive for vanA. However, after retesting the
negative samples with only the vanA primer set, 77 (88.5%) of 87 specimens
that were culture positive for Enterococcus faecium containing vanA were
positive by PCR. One specimen was PCR positive for the vanA gene but
culture negative for enterococci. The specificity of the vanA assay was
99.6%. PCR analysis of enrichment broth samples with all four primers sets
after 15 to 18 h of incubation detected 74 (85.1%) of the 87 culture-
positive specimens. The specificity of the vanA assay after the enrichment
step was 100%. No vanB-containing enterococci were recovered by culture.
Since 16 samples can be tested by PCR in 4 h (including electrophoresis),
identification of VRE is possible within 8 h of specimen submission at a
cost of approximately $10.12/assay. Thus, PCR may be a cost-effective
alternative to culture for surveillance of VRE in some hospitals.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Detection of vancomycin-resistant enterococci in fecal samples by PCR
Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
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