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Journal of Clinical Microbiology, June 2008, p. 2028-2037, Vol. 46, No. 6
0095-1137/08/$08.00+0     doi:10.1128/JCM.00818-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Metallo-β-Lactamase Detection: Comparative Evaluation of Double-Disk Synergy versus Combined Disk Tests for IMP-, GIM-, SIM-, SPM-, or VIM-Producing Isolates {triangledown}

Renata C. Picão,1* Soraya S. Andrade,2 Adriana Gianinni Nicoletti,1 Eloiza H. Campana,1 Gabriela C. Moraes,1 Rodrigo E. Mendes,1 and Ana C. Gales1,2

Laboratório ALERTA, Universidade Federal de São Paulo, São Paulo, Brazil,1 Laboratório Especial de Microbiologia Clínica, Universidade Federal de São Paulo, São Paulo, Brazil2

Received 17 April 2007/ Returned for modification 22 January 2008/ Accepted 28 February 2008

The emergence of metallo-β-lactamase (MBL)-producing isolates is a challenge to routine microbiology laboratories, since there are no standardized methods for detecting such isolates. The aim of this study was to evaluate the accuracy of different phenotypic methods to detect MBL production among Pseudomonas spp., Acinetobacter spp., and enterobacterial isolates, including GIM, IMP, SIM, SPM, and VIM variants. A total of 46 genetically unrelated Pseudomonas aeruginosa, Pseudomonas putida, Acinetobacter sp., and enterobacterial strains producing distinct MBLs were tested. Nineteen strains were included as negative controls. The inhibition of bacterial growth and β-lactam hydrolysis caused by MBL inhibitors (IMBL) also were evaluated. The isolates were tested for MBL production by both a double-disk synergy test (DDST) and a combined disk assay (CD) using imipenem and ceftazidime as substrates in combination with distinct IMBL. One hundred percent sensitivity and specificity were achieved by DDST using 2-mercaptopropionic acid in combination with ceftazidime and imipenem for the detection of MBL production among P. aeruginosa and Acinetobacter species isolates, respectively. The CD test showed the same results for detecting MBL-producing enterobacteria by combining imipenem and EDTA, with a 5.0-mm-breakpoint increase in the size of the inhibition zone. Our results indicate that both phenotypic methods to detect MBL-producing isolates should be based on the genera to be tested, regardless of the enzyme produced by such isolates, as well as on the local prevalence of MBL producers.

* Corresponding author. Mailing address: Rua Pedro de Toledo, 781, São Paulo, SP 04039-032, Brazil. Phone and fax: 55-11-5084-6538. E-mail: renata.picao{at}lemc.com.br

{triangledown} Published ahead of print on 5 March 2008.

Journal of Clinical Microbiology, June 2008, p. 2028-2037, Vol. 46, No. 6
0095-1137/08/$08.00+0     doi:10.1128/JCM.00818-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Qu, T.-t., Zhang, J.-l., Wang, J., Tao, J., Yu, Y.-s., Chen, Y.-g., Zhou, J.-y., Li, L.-j. (2009). Evaluation of Phenotypic Tests for Detection of Metallo-{beta}-Lactamase-Producing Pseudomonas aeruginosa Strains in China. J. Clin. Microbiol. 47: 1136-1142 [Abstract] [Full Text]  


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