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Journal of Clinical Microbiology, October 2001, p. 3633-3636, Vol. 39, No. 10
Medical Microbiology Division, Department of
Pathology University of Iowa College of Medicine, Iowa City,
Iowa1; Kinki University School of
Medicine, Ohnohigashi, Osakasayama, Osaka,
Japan2; and The JONES Group/JMI
Laboratories North Liberty, Iowa3
Received 2 May 2001/Returned for modification 18 June 2001/Accepted 18 July 2001
The Vitek automated susceptibility testing system with a modified
gram-positive susceptibility (GPS) 106 card (bioMerieux Vitek, Inc.,
Hazelwood. Mo.) and a rapid slide latex agglutination test (MRSA-Screen
test; Denka Seiken Co., Ltd., Tokyo, Japan) were evaluated for
their abilities to detect oxacillin resistance in
coagulase-negative staphylococci (CoNS). The reference broth microdilution method and the detection of the mecA gene by
PCR ("gold standard" reference result) were used to compare the
results obtained with the commercial products. A total of 123 clinical isolates consisting of eight species were selected from U.S.
surveillance collections. Among the mecA-positive isolates
(95 strains), 30 isolates were initially negative on the MRSA-Screen
test read at 3 min. When the agglutination reaction was extended for 10 min, 26 of the 30 isolates became positive. For a different four isolates, the oxacillin MIC was
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.10.3633-3636.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Comparison of the Vitek Gram-Positive Susceptibility 106 Card,
the MRSA-Screen Latex Agglutination Test, and mecA Analysis
for Detecting Oxacillin Resistance in a Geographically Diverse
Collection of Clinical Isolates of Coagulase-Negative
Staphylococci

0.25 µg/ml on the Vitek GPS 106 card. Among the mecA-negative isolates (28 strains), for
two Staphylococcus warneri, two S. lugdunensis,
and two S. saprophyticus strains MICs were
0.5
µg/ml by the reference broth microdilution method. Four of these
isolates were also categorized as resistant with the Vitek GPS 106 card
and two isolates were positive by the MRSA-Screen test. Overall, the
MRSA-Screen test, GPS 106 card, and reference broth microdilution
method had sensitivities of 95.7 (result at 10 min), 95.7, and 100%,
respectively, and specificities of 92.8, 85.7, and 78.5%,
respectively. Although the MRSA-Screen test required a slight
procedural modification, both commercial methods achieved a sensitivity
and specificity at detecting oxacillin resistance in CoNS at a level
that was acceptable for clinical laboratory use.
*
Corresponding author. Mailing address: 345 Beaver Kreek
Center, Suite A, North Liberty, IA 52317. Phone: (319) 665-3370. Fax: (319) 665-3371. E-mail: ronald-jones{at}jonesgr.com.
Present address: Department of Clinical Pathology, Kinki University
School of Medicine, 377-2, Ohnohigashi, Osakasayama, Osaka, Japan
589-8511.
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