Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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Indexed in KCI, KoreaMed, Synapse, DOAJ
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pISSN 2288-0585 eISSN 2288-6850

Evaluation of a Rapid Enrichment-PCR Method for the Detection of vanA Vancomycin-resistant Enterococci in Fecal Specimens

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2007 April Volume 10, Issue 1, pages 44-48.


https://doi.org/10.5145/ACM.2007.10.1.44

Evaluation of a Rapid Enrichment-PCR Method for the Detection of vanA Vancomycin-resistant Enterococci in Fecal Specimens

Sollip Kim1, Heungsup Sung1, Hong Sun Jeon1, Suk Ja Park1, Sang-Hyuk Park2, Mi-Na Kim1
1Department of Laboratory Medicine, Univertisy of Ulsan College of Medicine and Asan Medical Center, 2University of Ulsan College of Medicine, Seoul, Korea

Abstract

Background: Rapid and accurate surveillance is crucial in controlling vancomycin-resistant enterococci (VRE). Culture-based surveillance takes more than 4 days and direct polymerase chain reaction (PCR) is rapid but compromised by a low sensitivity. In this study, we evaluated the performance of an enrichment-PCR method for vanA VRE surveillance.

Methods: In July 2006, 100 fecal specimens were inoculated to Enterococcosel agar (EA) and Enterococcosel broth (EB) containing 6μg/mL vancomycin. After 1 or 2 day-incubation bacterial pellets were obtained from 1 mL of blackened EB and VanA PCR were performed with DNA extract of the pellets (EB+PCR). Blackened EB were also subcultured on EA (EB+ EA). Black colonies on EA were submitted to identification and antimicrobial susceptibility test and, if necessary, they were confirmed with vanA PCR. The electronic medical records were reviewed for previous history of colonization or infection of VRE.

Results: A total of 59 specimens were positive for VRE by at least one method. VanA VRE was detected from 43, 54, and 53 specimens by EA, EB+ PCR, and EB+EA, respectively; 54 EB+PCR positive specimens comprised 43 EA-positive, 7 EA-negative/ EA+EB-positive and 4 EB+PCR-only-positive, and 11 EA-negative/EB+PCR-positive specimens were from the previous VRE-colonizers. The five EB+PCR-negative specimens were EB+EA-positive, suggesting false negativity, probably due to PCR inhibitors. The average turn-around time for EA was 88±35 h, whereas 98% of EB+PCR positive results were obtained at day 1.

Conclusion: Enrichment in EB followed by PCR (EB+ PCR) appears to be a rapid and sensitive method for the detection of vanA VRE in stool specimens. Internal control would be required to detect false negative results. (Korean J Clin Microbiol 2007;10:44-48)

Keywords

Vanomycin-resistant enterococci, vanA PCR, Enrichment broth