New Delhi metallo-β-lactamase (NDM-1)-producing Klebsiella pneumoniae: case report and laboratory detection strategies

Abstract

The spread of antimicrobial resistance among Enterobacteriaceae is a significant clinical threat. We report the first case of an Enterobacteriaceae strain harboring the NDM-1 metallo-β-lactamase in a pediatric patient in the United States. We describe strategies for the detection of this novel resistance mechanism encountered in an isolate of Klebsiella pneumoniae.

Fig. 1.

Phenotypic detection of carbapenemases in a K. pneumoniae NDM-1 strain isolated from a nasal wash specimen (KP2). (A) Modified Hodge test, using ETP, for detection of carbapenemase, performed by the CLSI reference method. (B) Carbapenem-EDTA combined disk test for MBL. The K. pneumoniae isolate was inoculated to the surface of a Mueller-Hinton agar plate. Disks containing 10 μg/ml ETP, IMP, and MEM alone or ETP, IMP, and MEM plus 10 μl of 0.5 M EDTA (pH 8.0) were placed on the agar. EDTA was also added to a blank disk as a control. (C) EDTA-IMP disk synergy test for MBL. (D) Equivocal MBL Etest result demonstrating a large zone of inhibition. Arrowheads indicate the deformation of the ellipse (i.e., phantom zone). (E) Negative (control) MBL Etest results demonstrating a characteristic sharp-edged ellipse and a large zone of inhibition.