Sensitive EDTA-based microbiological assays for detection of metallo-beta-lactamases in nonfermentative gram-negative bacteria

• Autores: Marchiaro, Patricia; Mussi, María A.; Ballerini, Viviana; Pasteran, Fernando; Viale, Alejandro M.; Vila, Alejandro J.; Limansky, Adriana S.
• Año de publicación: 2005
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: Journal of Clinical Microbiology 2005; 43(11):5648-5652.
• Materia: Ácido Edético; beta-Lactamasas; Bacterias Gramnegativas
• Institución: Administración Nacional de Laboratorios e Institutos de Salud "Dr. Carlos G. Malbrán"

Fil: Marchiaro, Patricia. Universidad Nacional de Rosario. Departamento de Microbiología; Argentina.
Fil: Mussi, María A. Universidad Nacional de Rosario. Departamento de Microbiología; Argentina.
Fil: Ballerini, Viviana. Municipalidad de Rosario. Centro de Especialidades Me´dicas Ambulatorias de Rosario; Argentina.
Fil: Pasteran, Fernando. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Antimicrobianos; Argentina.
Fil: Viale, Alejandro M. Universidad Nacional de Rosario. Departamento de Microbiología; Argentina.
Fil: Vila, Alejandro J. Universidad Nacional de Rosario. Departamento de Química Biológica; Argentina.
Fil: Limansky, Adriana S. Universidad Nacional de Rosario. Departamento de Microbiología; Argentina.
The worldwide spread of metallo- -lactamase (MBL)-producing gram-negative bacilli represents a great concern nowadays. Sensitive assays for their specific detection are increasingly demanded to aid infection control and to prevent their dissemination. We have developed a novel microbiological assay employing crude bacterial extracts, designated EDTA-imipenem microbiological assay (EIM), to identify MBLs in nonfermentative gram-negative clinical strains. We also evaluated the ability of EIM to detect MBLs in comparison to those of other currently employed screening methods, such as the EDTA disk synergy test (EDS) with imipenem as a substrate and the Etest method. The sensitivities of EIM and Etest were similar (1 versus 0.92, respectively) and much higher than that of EDS (0.67). Moreover, both EIM and Etest displayed the maximum specificity. Modifications were introduced to EDS, including the simultaneous testing of three different -lactams (imipenem, meropenem, and ceftazidime) and two different EDTA concentrations. This resulted in a sensitivity improvement (0.92), albeit at a cost to its specificity. A simple strategy to accurately detect MBL producers is proposed; this strategy combines (i) an initial screening of the isolates by the extended EDS assay to select the potential candidates and (ii) confirmation of the true presence of MBL activity by EIM.