Skip to main content
  • ASM
    • Antimicrobial Agents and Chemotherapy
    • Applied and Environmental Microbiology
    • Clinical Microbiology Reviews
    • Clinical and Vaccine Immunology
    • EcoSal Plus
    • Eukaryotic Cell
    • Infection and Immunity
    • Journal of Bacteriology
    • Journal of Clinical Microbiology
    • Journal of Microbiology & Biology Education
    • Journal of Virology
    • mBio
    • Microbiology and Molecular Biology Reviews
    • Microbiology Resource Announcements
    • Microbiology Spectrum
    • Molecular and Cellular Biology
    • mSphere
    • mSystems
  • Log in
  • My alerts
  • My Cart

Main menu

  • Home
  • Articles
    • Current Issue
    • Accepted Manuscripts
    • COVID-19 Special Collection
    • Archive
    • Minireviews
  • For Authors
    • Submit a Manuscript
    • Scope
    • Editorial Policy
    • Submission, Review, & Publication Processes
    • Organization and Format
    • Errata, Author Corrections, Retractions
    • Illustrations and Tables
    • Nomenclature
    • Abbreviations and Conventions
    • Publication Fees
    • Ethics Resources and Policies
  • About the Journal
    • About JCM
    • Editor in Chief
    • Editorial Board
    • For Reviewers
    • For the Media
    • For Librarians
    • For Advertisers
    • Alerts
    • RSS
    • FAQ
  • Subscribe
    • Members
    • Institutions
  • ASM
    • Antimicrobial Agents and Chemotherapy
    • Applied and Environmental Microbiology
    • Clinical Microbiology Reviews
    • Clinical and Vaccine Immunology
    • EcoSal Plus
    • Eukaryotic Cell
    • Infection and Immunity
    • Journal of Bacteriology
    • Journal of Clinical Microbiology
    • Journal of Microbiology & Biology Education
    • Journal of Virology
    • mBio
    • Microbiology and Molecular Biology Reviews
    • Microbiology Resource Announcements
    • Microbiology Spectrum
    • Molecular and Cellular Biology
    • mSphere
    • mSystems

User menu

  • Log in
  • My alerts
  • My Cart

Search

  • Advanced search
Journal of Clinical Microbiology
publisher-logosite-logo

Advanced Search

  • Home
  • Articles
    • Current Issue
    • Accepted Manuscripts
    • COVID-19 Special Collection
    • Archive
    • Minireviews
  • For Authors
    • Submit a Manuscript
    • Scope
    • Editorial Policy
    • Submission, Review, & Publication Processes
    • Organization and Format
    • Errata, Author Corrections, Retractions
    • Illustrations and Tables
    • Nomenclature
    • Abbreviations and Conventions
    • Publication Fees
    • Ethics Resources and Policies
  • About the Journal
    • About JCM
    • Editor in Chief
    • Editorial Board
    • For Reviewers
    • For the Media
    • For Librarians
    • For Advertisers
    • Alerts
    • RSS
    • FAQ
  • Subscribe
    • Members
    • Institutions
Bacteriology

Evaluation of Spectra VRE, a New Chromogenic Agar Medium Designed To Screen for Vancomycin-Resistant Enterococcus faecalis and Enterococcus faecium

Jess F. Peterson, Christopher D. Doern, George Kallstrom, Katherine M. Riebe, Tara Sander, William Michael Dunne Jr., Nathan A. Ledeboer
Jess F. Peterson
2Department of Pathology, Medical College of Wisconsin, Milwaukee, Wisconsin
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Christopher D. Doern
4Department of Pathology and Immunology, Washington University, St. Louis, Missouri
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
George Kallstrom
4Department of Pathology and Immunology, Washington University, St. Louis, Missouri
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Katherine M. Riebe
1Dynacare Laboratories, Milwaukee, Wisconsin
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Tara Sander
3Department of Pathology, Children's Hospital of Wisconsin, Milwaukee, Wisconsin
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
William Michael Dunne Jr.
4Department of Pathology and Immunology, Washington University, St. Louis, Missouri
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Nathan A. Ledeboer
1Dynacare Laboratories, Milwaukee, Wisconsin
2Department of Pathology, Medical College of Wisconsin, Milwaukee, Wisconsin
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • For correspondence: nledeboe@mcw.edu
DOI: 10.1128/JCM.01676-10
  • Article
  • Figures & Data
  • Info & Metrics
  • PDF
Loading

ABSTRACT

Spectra VRE (Remel, Lenexa, KS) is a chromogenic medium designed to recover and differentiate vancomycin-resistant Enterococcus faecium and Enterococcus faecalis (VRE). This medium was compared to bile esculin azide agar (BEAV) and was 98.2% sensitive and 99.3% specific compared to BEAV, which was 87.6% sensitive and 87.1% specific at 24 h.

Two Enterococcus species, E. faecalis and E. faecium, cause the majority of human enterococcal infections (1). The rapid strain identification for patients colonized in the gastrointestinal tract with vancomycin-resistant strains of these species (VRE) is critical, as infection with these organisms can result in endocarditis, urinary tract, bloodstream, and wound infections with reduced therapeutic options (3). Screening for VRE is essential for the proper implementation of isolation precautions, as asymptomatic carriers serve as reservoirs for VRE infection or transmission (4, 7, 9). Successful identification of patients colonized with VRE requires rapid and accurate screening tests that are easily interpretable. The purpose of this multicenter study was to compare the performance of a new chromogenic medium, Spectra VRE, to bile esculin azide agar supplemented with 6 μg vancomycin/ml (BEAV; Remel) as a means of screening stool specimens for VRE colonization.

Stool specimens were collected from inpatients in sterile containers for Clostridium difficile testing and stored at 4°C for up to 3 days. Specimens were plated with a sterile Dacron swab to BEAV and Spectra VRE and streaked for isolation by the quadrant technique. Inoculated plates were incubated at 35°C in ambient air and examined for growth at 18, 24, and 48 h. Pink, purple, or dark blue colonies on Spectra VRE were presumptively identified as vancomycin-resistant E. faecium. Light blue colonies on Spectra VRE were presumptively identified as vancomycin-resistant E. faecalis. Presumed VRE colonies on BEAV appeared dark brown or black.

Presumptive VRE from Spectra VRE and BEAV were subcultured to tryptic soy agar plates (TSA; Remel) and incubated at 35°C for 24 h. Catalase-negative, Gram-positive cocci positive for l-pyrrolidonyl-β-naphthylamide (PYR; Remel) were further identified using methyl-α-d-glucopyranoside (MDG; Remel), motility test medium (Remel), PB arabinose (Remel), and colony morphology on blood agar. VRE isolates were identified based on the following performance characteristics: E. faecalis, MDG-negative, nonmotile, arabinose-negative, white colonies; E. faecium, MDG-negative, nonmotile, arabinose-positive, gray colonies. The Etest (bioMérieux, Durham, NC) was performed to determine the vancomycin MIC of each isolate. Breakpoints for VRE were interpreted as defined by CLSI guidelines (2). Confirmatory identification and antimicrobial susceptibility testing were also performed with the Vitek 2 (bioMérieux). All confirmed VRE isolates from Spectra VRE agar were identified by 16S rRNA gene sequencing using the MicroSeq 500 protocol (Applied Biosystems, Carlsbad, CA). Generated sequences were analyzed using the Basic Local Assignment Search Tool (BLAST), a search engine provided by the National Center for Biotechnology Information (NCBI).

Appropriately colored colonies growing on either medium, confirmed as VRE by sequencing and vancomycin MIC ≥ 32 mg/ml, served as the gold standard for this study. The combined sensitivity and specificity of Spectra VRE were 91.2% and 99.7% following 18 h of incubation, 98.2% and 99.3% at 24 h, and 99.1% and 96.5% at 48 h, respectively (Table 1). Two of the three false positives reported at site A were attributed to the growth of single light blue colonies that were both identified as vancomycin-sensitive E. faecalis. The remaining false-positive isolate produced multiple pink colonies and was identified as a Lactobacillus sp. Four of the seven false positives reported at site B produced pink colonies that were identified as Gram-positive bacilli. Two of the seven false positives produced blue colonies that were identified as Pediococcus spp. The remaining false-positive isolate, which produced blue-green colonies, was identified as Enterococcus durans. In addition, one false-negative result was reported from site B in which vancomycin-resistant E. faecium was recovered on BEAV at 24 h and demonstrated no growth on Spectra VRE after 48 h of incubation.

By comparison, the combined sensitivity and specificity of BEAV for the detection of VRE at 18, 24, and 48 h were 73.5% and 90.2%, 87.6% and 87.1%, and 93.8% and 72.4%, respectively (Table 1). The reduced specificity of BEAV agar stemmed from the growth of Lactobacillus spp., Lactococcus spp., Pediococcus spp., and Enterococcus spp. other than E. faecalis or E. faecium at both trial sites (Fig. 1). The combined positive predictive value (PPV) and negative predictive value (NPV) of both media are shown in Table 1.

Colonies recovered from site A on Spectra VRE were differentiated based on pink, purple, dark, or light blue pigmentation. A total of 51 vancomycin-resistant E. faecium isolates were recovered on Spectra VRE. The sensitivity of Spectra VRE based on colony pigmentation alone at 18, 24, and 48 h was 94.1%, 98.0%, and 100.0%, respectively. For site B, the process for colony selection and identification was similar, but this group did not differentiate between dark and light blue colonies. A total of 61 vancomycin-resistant E. faecium isolates and 1 vancomycin-resistant E. faecalis isolate were recovered on Spectra VRE at site B. The sensitivity of Spectra VRE at site B (based on colony pigmentation) was 88.7% at 18 h and 98.4% at 24 and 48 h. Independent clinical trial site analyses of Spectra VRE and BEAV are shown in Table 2. Differences in sensitivity of BEAV at 18 and 24 h at sites A and B may have been due to reading technique or different circulating clones of VRE; regardless, data from both sites highlight the lack of sensitivity and specificity when using BEAV to screen for VRE.

VRE isolates recovered on Spectra VRE were sequenced for identification. Two discrepancies were observed between the Vitek 2, biochemical testing, and sequence analyses. Several pink colonies recovered at 24 h of incubation were identified as E. faecium by the Vitek 2 and biochemical testing but were most closely related to E. faecalis by sequence analysis (99% identification). Similarly, several light blue colonies observed at 18 h of incubation were identified by the Vitek 2 and biochemical testing as E. faecalis but by sequencing as E. faecium (98% identification).

The rapid detection of VRE colonization is critical for proper infection control. Traditional culture methods that rely on colony morphology, biochemical characteristics, and susceptibility testing may take up to 5 days, thus prolonging effective patient management (8). Several chromogenic media have been developed to date, including chromID VRE (bioMérieux) (6) and CHROMagar VRE (BD, Baltimore, MD) (5), that detect VRE rapidly with high sensitivity and specificity. The data presented in this report demonstrate that Spectra VRE can also rapidly identify VRE with high sensitivity and specificity following 24 h of incubation, regardless of the ability to differentiate to species, when distinguishing VRE from common stool flora based on pink-, purple-, or blue-pigmented colonies.

FIG. 1.
  • Open in new tab
  • Download powerpoint
FIG. 1.

Growth of contaminants on each medium at 18, 24, and 48 h. Contaminants are classified as potential false-positive isolates. Colonies demonstrating any hue of pink, purple, or blue were classified as potentially false positive on Spectra VRE; isolates with a brown-black hue were classified as potentially false positive on BEAV.

View this table:
  • View inline
  • View popup
TABLE 1.

Analysis of Spectra VRE and BEAV for the detection of VRE from 399 fecal specimens at 18, 24, and 48 h (combined data)

View this table:
  • View inline
  • View popup
TABLE 2.

Analysis of Spectra VRE and BEAV for the detection of VRE from fecal specimens at 18, 24, and 48 h (individual clinical trial site results)

FOOTNOTES

    • Received 18 August 2010.
    • Returned for modification 24 September 2010.
    • Accepted 3 October 2010.
  • Copyright © 2010 American Society for Microbiology

REFERENCES

  1. 1.↵
    Cetinkaya, Y., P. Falk, and G. C. Mayhall. 2000. Vancomycin-resistant enterococci. Clin. Microbiol. Rev. 13 : 686-707.
    OpenUrlAbstract/FREE Full Text
  2. 2.↵
    Clinical and Laboratory Standards Institute. 2009. Performance standards for antimicrobial susceptibility testing; 19th informational supplement M100-S19. NCCLS, Wayne, PA.
  3. 3.↵
    Harbarth, S. Cosgrove, and Y. Carmeli. 2002. Effects of antibiotics on nosocomial epidemiology of vancomycin-resistant enterococci. Antimicrob. Agents Chemother. 46 : 1619-1628.
    OpenUrlFREE Full Text
  4. 4.↵
    Huh, J. Y., W. G. Lee, and H. Y. Jin. 2006. Molecular characterization on vancomycin-resistant enterococci from clinical and surveillance specimens. Infect. Control Hosp. Epidemiol. 27 : 1076-1080.
    OpenUrlCrossRefPubMed
  5. 5.↵
    Kallstrom, G., C. D. Doern, and W. M. Dunne. 2010. Evaluation of a chromogenic agar under development to screen for VRE colonization. J. Clin. Microbiol. 48 : 999-1001.
    OpenUrlAbstract/FREE Full Text
  6. 6.↵
    Ledeboer, N. A., K. Das, M. Eveland, C. Roger-Dalbert, S. Mailler, S. Chatellier, and W. M. Dunne. 2007. Evaluation of a novel chromogenic agar medium for isolation and differentiation of vancomycin-resistant Enterococcus faecium and Enterococcus faecalis isolates. J. Clin. Microbiol. 45 : 1556-1560.
    OpenUrlAbstract/FREE Full Text
  7. 7.↵
    Ostrowsky, B. E., W. E. Trick, A. H. Sohn, S. B. Quirk, S. Holt, L. A. Carson, B. C. Hill, M. J. Arduino, M. J. Kuehnert, and W. R. Jarvis. 2001. Control of vancomycin-resistant enterococcus in health care facilities in a region. N. Engl. J. Med. 344 : 1427-1433.
    OpenUrlCrossRefPubMedWeb of Science
  8. 8.↵
    Palladino, S., I. D. Kay, J. P. Flexman, I. Boehm, A. G. Costa, E. J. Lambert, and K. J. Christiansen. 2003. Rapid detection of vanA and vanB genes directly from clinical specimens and enrichment broths by real-time multiplex PCR assay. J. Clin. Microbiol. 41 : 2483-2486.
    OpenUrlAbstract/FREE Full Text
  9. 9.↵
    Trick, W. E., S. M. Paule, S. Cunningham, R. L. Cordell, M. Lankford, V. Stosor, S. L. Solomon, and L. R. Peterson. 2004. Detection of vancomycin-resistant enterococci before and after antimicrobial therapy: use of conventional culture and polymerase chain reaction. Clin. Infect. Dis. 38 : 780-786.
    OpenUrlCrossRefPubMed
PreviousNext
Back to top
Download PDF
Citation Tools
Evaluation of Spectra VRE, a New Chromogenic Agar Medium Designed To Screen for Vancomycin-Resistant Enterococcus faecalis and Enterococcus faecium
Jess F. Peterson, Christopher D. Doern, George Kallstrom, Katherine M. Riebe, Tara Sander, William Michael Dunne Jr., Nathan A. Ledeboer
Journal of Clinical Microbiology Nov 2010, 48 (12) 4627-4629; DOI: 10.1128/JCM.01676-10

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
Print

Alerts
Sign In to Email Alerts with your Email Address
Email

Thank you for sharing this Journal of Clinical Microbiology article.

NOTE: We request your email address only to inform the recipient that it was you who recommended this article, and that it is not junk mail. We do not retain these email addresses.

Enter multiple addresses on separate lines or separate them with commas.
Evaluation of Spectra VRE, a New Chromogenic Agar Medium Designed To Screen for Vancomycin-Resistant Enterococcus faecalis and Enterococcus faecium
(Your Name) has forwarded a page to you from Journal of Clinical Microbiology
(Your Name) thought you would be interested in this article in Journal of Clinical Microbiology.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Share
Evaluation of Spectra VRE, a New Chromogenic Agar Medium Designed To Screen for Vancomycin-Resistant Enterococcus faecalis and Enterococcus faecium
Jess F. Peterson, Christopher D. Doern, George Kallstrom, Katherine M. Riebe, Tara Sander, William Michael Dunne Jr., Nathan A. Ledeboer
Journal of Clinical Microbiology Nov 2010, 48 (12) 4627-4629; DOI: 10.1128/JCM.01676-10
del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo
  • Top
  • Article
    • ABSTRACT
    • FOOTNOTES
    • REFERENCES
  • Figures & Data
  • Info & Metrics
  • PDF

KEYWORDS

bacteriological techniques
culture media
Enterococcus faecalis
Enterococcus faecium
Gram-Positive Bacterial Infections
vancomycin resistance

Related Articles

Cited By...

About

  • About JCM
  • Editor in Chief
  • Board of Editors
  • Editor Conflicts of Interest
  • For Reviewers
  • For the Media
  • For Librarians
  • For Advertisers
  • Alerts
  • RSS
  • FAQ
  • Permissions
  • Journal Announcements

Authors

  • ASM Author Center
  • Submit a Manuscript
  • Article Types
  • Resources for Clinical Microbiologists
  • Ethics
  • Contact Us

Follow #JClinMicro

@ASMicrobiology

       

ASM Journals

ASM journals are the most prominent publications in the field, delivering up-to-date and authoritative coverage of both basic and clinical microbiology.

About ASM | Contact Us | Press Room

 

ASM is a member of

Scientific Society Publisher Alliance

 

American Society for Microbiology
1752 N St. NW
Washington, DC 20036
Phone: (202) 737-3600

 

Copyright © 2021 American Society for Microbiology | Privacy Policy | Website feedback

Print ISSN: 0095-1137; Online ISSN: 1098-660X