Rapid detection of carbapenemase-producing Enterobacteriaceae

Abstract

To rapidly identify carbapenemase producers in Enterobacteriaceae, we developed the Carba NP test. The test uses isolated bacterial colonies and is based on in vitro hydrolysis of a carbapenem, imipenem. It was 100% sensitive and specific compared with molecular-based techniques. This rapid (<2 hours), inexpensive technique may be implemented in any laboratory.

Figure 1

Representative results of the Carba NP test. The Carba NP test was performed with a noncarbapenemase producer (Escherichia coli producing the extended-spectrum β-lactamase CTX-M-15, upper panel) and with a carbapenemase producer (Klebsiella pneumoniae–producing New Delhi metallo-β-lactamase-1, lower panel) in a reaction medium without (left panel) and with (right panel) imipenem. Uninoculated wells are shown as controls. Photographs were taken after a 1.5-hour incubation.

Figure 2

Strategy for identification of carbapenemase-producing Enterobacteriaceae. The time needed to perform the test is indicated before each test. The number of flasks indicates the degree of specialization needed to perform the test; the number of $ indicates the relative cost of each test.