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Jung and Lee: Evaluation of MicroScan Synergies plus Positive Combo 3 Panels for Identification and Antimicrobial Susceptibility Testing of Staphylococcus aureus and Enterococcus Species
Original Article

Korean J Leg Med 2010;30(4):373-380.

Published online: 14 January 2010

DOI: https://doi.org/10.3343/kjlm.2010.30.4.373

Evaluation of MicroScan Synergies plus Positive Combo 3 Panels for Identification and Antimicrobial Susceptibility Testing of Staphylococcus aureus and Enterococcus Species

Haiyoung Jung, M.D., Nam Yong Lee, M.D.

Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

Corresponding author: Nam Yong Lee, M.D. Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Korea Tel: +82-2-3410-2706, Fax: +82-2-3410-2719 E-mail: micro.lee@samsung.com

      Revised 28 January 201028 May 2010       Accepted 9 July 2010

Copyright © 2010 Korean Society for Legal Medicine

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background:

Few studies have evaluated the performance of the recently introduced MicroScan Synergies plus Positive Combo 3 Panels (SIPC3) (Dade Behring Inc., USA). We evaluated the clinical efficacy of the panels in identification (ID) and antimicrobial susceptibility testing (AST) of Staphylococcus aureus and enterococci.

Methods:

To evaluate the panels' accuracy of identification, the results obtained using the test panels were compared with those obtained by using conventional biochemical tests in conjunction with VITEK 2 system (bio-Merieux, USA). In addition, the AST results obtained using the panels were compared with those obtained by performing CLSI broth microdilution.

Results:

The overall agreement between the approaches for the ID of S. aureus and enterococci was 100% and 96%, respectively. The categorical and essential agreements (CA and EA) for S. aureus were 98%, each. Very major errors (VME), major errors (ME), and minor error (mE) for S. aureus were 0.45%, 0.3%, and 4.2%, respectively. The majority of VMEs were for oxacillin (8.6%), penicillin (2.0%), erythromycin (7.9%), clindamycin (3.8%), and tetracycline (4.1%). For enterococci, the CA, EA, VME, ME, and mE were 88.8%, 93.7%, 4.4%, 0%, and 2.8%, respectively. The 80.5% (29/36) of Enterococcus faecium had concordant ID with the reference. Most of the categorical errors (3 VMEs and 14 mEs) were observed for quinupristin/dalfopristin (Synercid; Catalytica Pharmaceuticals Inc., USA).

Conclusions:

The panels compared favorably with conventional methods for the ID and AST of S. aureus. However, we expected a better performance for ID of E. faecium and AST using Synercid.

Keywords: Staphylococcus aureus, Enterococcus, MicroScan Synergies plus Positive Combo 3 Panels

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Table 1.
Comparison of identification results obtained using MicroScan Synergies plus Positive Combo 3 Panels and conventional biochemical tests in conjunction with VITEK 2 system
Clinical isolates (identified using biochemical tests and VITEK 2 GP ID card) N of isolates MicroScan results (%)
Concordant with the clinical ID Discordant with the clinical ID ID up to the genus level No ID
S. aureus 100 100 (100) - - -
Subtotal 100 100 (100) - - -
E. faecium 36 29 (80.5) 3 (8.3) 3 (8.3) 1 (2.8)
E. faecalis 62 62 (100) - - -
E. gallinarum 1 1 (N/A) - - -
E. casseliflavus 1 0 (N/A) 1 (N/A) - -
Subtotal 100 92 (92.0) 4 (4.0) 3 (3.0) 1 (1.0)

Abbreviations: ID, identification; N/A, not applicable; S. aureus, Staphylococcus aureus; E. faecium, Enterococcus faecium; E. faecalis, Enterococcus faecalis; E. gallinarum, Enterococcus gallinarum; E. casseliflavus, Enterococcus casseliflavus.

Table 2.
Comparison of oxacillin MICs in Staphylococcus aureus determined by CLSI broth microdilution and MicroScan
CLSI broth microdilution oxacillin MIC (μg/mL) N of S. aureus strains
MicroScan oxacillin MIC (μg/mL)
≤0.12 0.25 0.5 >2 Total
≤0.12 1 1 0 0 2
0.25 2 9 5 0 15
0.5 1∗ 7 9 0 17
32 0 0 0 3 3
64 0 0 1∗ 4 5
>64 0 2∗ 0 55 57
Total 4 19 15 62 100

∗ Cases that did not satisfy essential agreement, which was defined as MICs between the 2 systems within plus or minus one doubling dilution. Abbreviations: MIC, minimum inhibitory concentration; S. aureus, Staphylococcus aureus.

Table 3.
Results of AST for Staphylococcus aureus
Antibiotic agent Total N EA (%) CA (%) N of isolates N (%) of isolates
S I R mE ME VME
Oxacillin 100 96 97 65 0 35 0 0 3 (8.6)
Penicillin 100 98 98 2 0 98 0 0 2 (2.0)
Erythromycin 100 95 95 62 0 38 1 (1.0) 1 (0.2) 3 (7.9)
Clindamycin 100 96 97 47 0 53 0 1 (2.1) 2 (3.8)
Tetracycline 100 98 96 49 2 49 2 (2.0) 0 2 (4.1)
T/S 100 99 99 88 0 12 0 1 (1.1) 0
Rifampin 100 99 99 96 0 4 0 0 1 (25)
Gentamicin 100 99 99 56 0 44 0 0 1 (2.3)
Vancomycin 100 100 100 100 0 0 0 0 0
Teicoplanin 100 100 100 100 0 0 0 0 0

Abbreviations: AST, antimicrobial susceptibility test; EA, essential agreement; CA, categorical agreement; S, susceptible; I, intermediate; R, resistant; mE, minor error; ME, major error; VME, very major error; T/S, trimethoprim/sulfamethoxazole.

Table 4.
Comparison of vancomycin MICs in Enterococcus species determined by CLSI broth microdilution and MicroScan
CLSI broth microdilution vancomycin MIC (μg/mL) N of Enterococcus species strains
MicroScan vancomycin MIC (μg/mL)
≤1 2 4 16 >16 Total
0.5 16 0 0 0 0 16
1 40 2 0 0 0 42
2 2 25 3 1∗ 0 31
4 0 1∗ 2 0 0 3
>64 1∗ 0 0 0 6 7
Total 59 28 5 1 6 99

∗ Cases that did not show essential agreement, which was defined as MICs between the 2 systems within plus or minus one doubling dilution.

Abbreviations: MIC, minimum inhibitory concentration.

Table 5.
Results for enterococcal susceptibility test
Antibiotic agent Total N EA (%) CA (%) N of isolates N (%) of isolates
S I R mE ME VME
Ampicillin 99 99.0 99.0 65 0 34 0 0 1 (2.9)
Penicillin 99 94.9 99.0 58 0 41 0 0 1 (2.4)
Vancomycin 99 97.0 98.0 92 0 7 1 (1.1) 0 1 (14.3)
Teicoplanin 99 100 97.0 95 4 2 3 (3.2) 0 0
Tetracycline 99 83.8 98.0 53 0 46 1 (1.9) 0 1 (2.2)
Streptomycin (S) 99 N/A 99.0 69 0 30 0 0 1 (3.3)
Gentamicin (S) 99 N/A 98.0 45 0 54 0 0 2 (3.7)
Synercid∗ 31 74.2 61.3 19 0 12 9 (47.4) 0 3 (25.0)

∗ Enterococcus faecium only.

Abbreviations: EA, essential agreement; CA, categorical agreement; S, susceptible; I, intermediate; R, resistant; mE, minor error; ME, major error; VME, very major error; (S), Synergy Screen; N/A, not applicable; Synercid, quinupristin/dalfopristin.

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