CarbAcineto NP test for rapid detection of carbapenemase-producing Acinetobacter spp

Abstract

Multidrug-resistant Acinetobacter baumannii isolates, particularly those that produce carbapenemases, are increasingly reported worldwide. The biochemically based Carba NP test, extensively validated for the detection of carbapenemase producers among Enterobacteriaceae and Pseudomonas spp., has been modified to detect carbapenemase production in Acinetobacter spp. A collection of 151 carbapenemase-producing and 69 non-carbapenemase-producing Acinetobacter spp. were tested using the Carba NP test and a modified Carba NP protocol (the CarbAcineto NP test) in this study. The CarbAcineto NP test requires modified lysis conditions and an increased bacterial inoculum compared to those of the original Carba NP test. The Carba NP test detects metallo-β-lactamase producers but failed to detect the production of other carbapenemase types among Acinetobacter spp. In contrast, the newly designed CarbAcineto NP test, which is rapid and reproducible, detects all types of carbapenemases with a sensitivity of 94.7% and a specificity of 100%. This cost-effective technique offers a reliable and affordable technique for identifying carbapenemase production in Acinetobacter spp., which is a marker of multidrug resistance in those species. Its use will facilitate the recognition of these carbapenemases and prevent their spread.

FIG 1

Representative results obtained using the CarbAcineto NP test on Acinetobacter spp. isolates. (A) Representative results obtained using the CarbAcineto NP test on wild-type (WT), narrow-spectrum β-lactamase-producing (OXA-21 and RTG-4), and extended-spectrum β-lactamase-producing Acinetobacter spp. (PER-1, VEB-1, and SHV-5). (B) Representative results obtained using the CarbAcineto NP test on acquired carbapenemase-producing Acinetobacter spp. isolates. Ambler class A (GES-types), Ambler class B (IMP-type and NDM-type), and Ambler class D (OXA-23, OXA-24/OXA-40, OXA-58, and OXA-143) carbapenemases are represented. (C) Representative result obtained using the CarbAcineto test on a carbapenem-resistant Acinetobacter sp. overexpressing its chromosome-encoded OXA-51 β-lactamase. (D) Representative result of a noninterpretable result using the CarbAcineto NP on a wild-type Acinetobacter isolate.