Evaluation of the MicroScan NegCombo Panel Type 44 for Detection of Extended-Spectrum beta-Lactamase among Clinical Isolates of Escherichia coli, Klebsiella species, and Proteus mirabilis / 대한진단검사의학회지

BACKGROUND: Accurate and rapid detection of extended-spectrum beta-lactamases (ESBLs) is important in guiding proper antimicrobial therapy for infected patients. We evaluated the performance of MicroScan NegCombo Type 44 panel (Dade Behring, USA), which was developed to confirm ESBL-producing Enterobacteriaceae using ceftazidime/clavulanate and cefotaxime/clavulanate. METHODS: From August 30 to September 20, 2007, 206 non-duplicate clinical isolates, including 106 Escherichia coli, 81 Klebsiella pneumoniae, 11 Klebsiella oxytoca, and 8 Proteus mirabilis were subcultured and tested with Type 32 and Type 44 panels. The results were compared with those of the CLSI phenotypic confirmatory test (CLSI-PCT) and disk approximation test (DAT). Isolates not susceptible to cefotetan or flagged as "Possible ESBL, unable to interpret confirm test (Possible ESBL)" on Type 44 panel were tested with boronic acid disks to confirm AmpC beta-lactamases (AmpC) production. RESULTS: Of the 206 isolates tested, 44 (21.4%) produced ESBL by CLSI-PCT or DAT, including 27 E. coli, 14 K. pneumoniae, 2 K. oxytoca, and 1 P. mirabilis. Thirty-eight isolates flagged as "Confirmed ESBL" on Type 44 panel were all confirmed as ESBL-producers. Of 14 K. pneumoniae flagged as "Possible ESBL", 6 were confirmed as ESBL and AmpC co-producers and 8 as AmpC-producers. CONCLUSIONS: Type 44 panel showed an excellent performance in detecting ESBL-producing E. coli, Klebsiella spp., and P. mirabilis. When flagged as "Confirmed ESBL", no other confirmatory test was necessary to report as ESBL; however, "Possible ESBL" required a differential test for AmpC production.

New Method for Detecting Plasmid-mediated AmpC Beta-lactamases / 中华医院感染学杂志

OBJECTIVE To establish a convenient method for detecting plasmid-mediated AmpC beta-lactamases in Enterobacteriaceae lacking chromosomal AmpC beta-lactamases and to investigqte their genotype.METHODS Fifteen isolates of Klebsiella pneumoniae were collected and the diameters of inhibitory zone of cefoxitin in combination with or without cloxacillin were measured separately by standard disc diffusion test.The M3D assay was used as control method.And the activity of AmpC beta-lactamases of all isolates was simultaneously assayed.Multiplex PCR was performed to determine the genotype of AmpC beta-lactamases.RESULTS Among 15 isolates,8 isolates were identified to have plasmid-mediated AmpC beta-lactamases.The sensitivity and specificity of AmpC beta-lactamases phenotypic confirmatory test were 100%.Eight of 15 isolates were identified to be DHA-1 beta-lactamases by multiplex PCR.CONCLUSIONS The new AmpC beta-lactamases phenotypic confirmatory test is a reliable method for detecting plasmidmediated AmpC beta-lactamases in Enterobacteriaceae lacking chromosomal AmpC beta-lactamases.DHA-1 beta-lactamases are the main genotypes of plasmid-mediated AmpC beta-lactamases in Hubei Province of China.