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

6

Weeks in Review

2

Weeks to Publication
Indexed in KCI, KoreaMed, Synapse, DOAJ
Open Access, Peer Reviewed
pISSN 2288-0585 eISSN 2288-6850

Use of Methyl-α-D-glucopyranoside Test for Species Identification of Vancomycin Resistant Enterococci

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 1999 June Volume 2, Issue 1, pages 71-76.

Use of Methyl-α-D-glucopyranoside Test for Species Identification of Vancomycin Resistant Enterococci

Mi-Na Kim, M.D., Heung-Sub Sung, M.D., Jun Seok Park, M.D. and Chik Hyun Pai, M.D.

Department of Clinical Pathology, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea

Abstract

Background:The precise identification of Enterococcus gallinarum and E. casseliflavus has assumed additional importance in clinical microbiology due to the intrinsic low-level resistance to vancomycin and the difficulty in differentiating them from E. faecium or E. faecalis, which are frequently found to be clinically significant vancomycin resistant enterococci(VRE). We evaluated the usefulness of Methyl-α-D-glucopyranoside(MDG) test for accurate species identification among them.

Methods:A total of 23 enterococci isolates including 18 clinical isolates of VRE from Nov 1997 to Aug 1998 and 5 VRE strains which had previously been reported as E. faecalis (2), E. faecium(2), E. avium(1) carrying vanC were tested for acidification of MDG. MDG test was done using 1% MDG in phenol red broth base and yellow coloration was interpreted as positive after 1 and 2 days of incubation at 35℃. MDG results were compared with species identification by MicroScan Pos Combo type 6 (Dade, USA), motility test, pigment production, and PCR results of vanA, vanB, vanC1, vanC2/C3. 

Results:Vancomycin resistance of 23 strains were genotyped as 7 strains of vanA, 12 strains of vanC1, 4 strains of vanC2/C3. MicroScan identified 7 vanA VRE as E. faecalis(1) and E. faecium(6), 12 VRE carrying vanC1 as E. faecalis(3), E. faecium(8) and E. avium(1), and 4 VRE carrying vanC2/C3 as E. faecalis(3) and E. avium(1). Sixteen vanC VRE strains were all positive for MDG test and only 8(50%) of the 16 strains were motile. Yellow pigment were detected in all 4 vanC2/C3 VRE but only after a careful examination with a prolonged incubation. Seven vanA VRE were all negative in MDG tests, motility test and pigment production.

Conclusions:MicroScan system plus motility and pigment production test was not able to differentiate reliably E. gallinarum and E. casseliflavus from E. faecalis and E. faecium. The MDG test was shown to be superior to motility test in differentiating those from E. faecalis and E. faecium. We conclude that the MDG test should be included for identifcation of VRE. (Korean J Clin Microbiol 1999;2:71~76)

Keywords

Methyl- α-D-glucopyranoside, Vancomycin resistant enterococci(VRE), vanC, Species identification