Lab Med Online.  2013 Oct;3(4):264-268.

Occurrence of a PCR-Positive but Culture-Negative Case for vanB Vancomycin-Resistant Enterococci in Stool Surveillance

• Won D
• Hong KH
• Yun K
• Sung H
• Kim MN

Abstract

We present here occurence of PCR-positive but culture-negative for vanB vancomycin-resistant enterococci (VRE) from an enrichment broth of a stool surveillance culture in a patient suffering from Parkinson's disease, who was transferred from a long-term care facility because of aspiration pneumonia. He developed VRE bacteriuria at the hospital day 42. vanA and vanB genes were detected from 6 microg/mL vancomycin-containing BBL Enterococcosel broth (BD), of which color changed to black after overnight incubation, by both Seeplex VRE detection (Seegene, Seoul, Korea) and Anyplex VanR real-time PCR (Seegene). Subculture of an aliquot of the blackened broth on blood agar plate produced only vanA VRE. All of the four subsequent consecutive surveillance cultures for 1 month until discharge at hospital day 75 resulted in PCR-positive but culture-negative for vanB VRE from the enrichment broths. Therefore, the presence of a non-enterococcal intrinsic reservoir bearing vanB is more likely than low burden of vanB VRE. Considering the rare occurrence of vanB VRE in Korea, vanB-positive PCR results from the enrichment broth requires confirmation by microbiological studies.

Keyword

Vancomycin; Enterococcus; vanB; PCR; Enrichment; Broth; Surveillance; Culture; Stool

MeSH Terms

Agar
Bacteriuria
Enterococcus
Humans
Korea
Long-Term Care
Parkinson Disease
Pneumonia, Aspiration
Polymerase Chain Reaction
Real-Time Polymerase Chain Reaction
Stress, Psychological
Ursidae
Vancomycin
Agar
Vancomycin

Figure

• 

  Fig. 1 PCR results for vanA and vanB on enrichment broth culture. (A) Agarose gel electrophoresis of PCR products using Seeplex VRE Detection kit (Seegene). Lane 1, synthetic marker included in the Seeplex kit; 2 and 3, positive for both vanA and vanB at the first PCR and the second PCR; 4, negative control; 5, synthetic positive control for vanA and vanB included in the Seeplex kit. (B) Amplification curve of real-time PCR using Anyplex VanR Real-Time PCR (Seegene). The tested sample showed the curves positive for vanA with Ct of 24.93 and vanB with Ct of 27.67.

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