Abstract
Rapid and accurate detection can help optimize patient treatment and improve infection control against nosocomial carbapenemase-producing organisms (CPO). In this study, a total of 217 routine clinical isolates (Enterobacterales and A. baumannii), including 178 CPOs and 39 non-CPOs, were tested to evaluate the performance of six phenotypic carbapenemase detection and classification assays, i.e., BD Phoenix CPO detect panel, Rapidec Carba-NP, O.K.N detection kit, and three carbapenem inactivation methods (CIMs; mCIM, eCIM, sCIM). The overall detection sensitivity and specificity were 98.78% (95.21–99.79%) and 79.49% (63.06–90.13%), respectively, for the BD phoenix CPO P/N test; 91.93% (86.30–95.45%) and 100% (88.83–100%), respectively, for the Rapidec Carba-NP; 98.06% (94.00–99.50%) and 97.44% (84.92–99.87%), respectively, for mCIM; and 96.89% (92.52–98.85%) and 94.87% (81.37–99.11%), respectively, for sCIM. The classification sensitivity and specificity for the BD phoenix CPO Ambler test, the O.K.N detection kit, and the mCIM and eCIM were 56.71% (48.75–64.34%) and 94.87% (81.37–99.11%), 99.28% (95.43–99.96%) and 100% (88.83–100%), and 92.90% (87.35–96.23%) and 97.44% (84.92–99.87%), respectively. All detection assays were reliable in detecting carbapenemase. However, the Rapidec Carba-NP and mCIM were insufficient in detecting OXA-48-like enzymes. The BD phoenix CPO detect panel had a strong ability to detect carbapenemase but failed to classify 48/59 (81.36%) KPC, 8/52 (15.38%) NDM, 8/22 (36.36%) OXA-23-like, and 6/11 (54.55%) dual enzymes. The O.K.N detection kit accurately detected and differentiated KPC, NDM, and OXA-48-like enzymes existing alone or in combination. The results of this study will support reliable laboratory work tools and promote therapeutic and infection control decisions.
Highlights
Carbapenems are considered as the last resort to defend against severe multidrugresistant Gram-negative bacterial infections owing to their broad spectrum of activity and stability to most β-lactamases [1]
To improve carbapenemase detection and classification, this study evaluated the performance of three commercial diagnostic kits—BD Phoenix carbapenem-producing organisms (CPOs) detect panel, Rapidec Carba-NP, and an O.K.N detection kit—and three carbapenem inactivation methods (CIMs)—mCIM, eCIM, and the simplified version sCIM—using clinical isolates collected in China
The high sensitivity of the BD Phoenix CPO detect panel P/N test observed in this study supports the direct reporting of CPO-negative strains without additional tests, and directly provides the true carbapenem MICs that can be used as a screening value for carbapenemase
Summary
Carbapenems are considered as the last resort to defend against severe multidrugresistant Gram-negative bacterial infections owing to their broad spectrum of activity and stability to most β-lactamases [1]. Gram-negative organisms become carbapenemsresistant mainly through carbapenemase production, cephalosporinase (AmpC), and/or extended-spectrum β-lactamase (ESBL) expression in combination with porin-encoding genes (such as oprD) mutation and/or efflux pump (such as MexAB-OprM, MexXY-OprM, MexCD-OprJ) overexpression, which lead to limited cell membrane permeability [2,3,4,5]. Carbapenemase, a primary mechanism of carbapenem resistance in Gram-negative bacteria, is mainly encoded on plasmids and is highly transmissible [6]. Carbapenem-producing organisms (CPOs) have become increasingly prevalent worldwide, and infections caused by carbapenem-resistant organisms, especially CPOs, are associated with limited clinical treatment options, a high mortality rate, and a heavy healthcare burden. Genetic detection methods are considered to be the gold standard, such as traditional PCR, Xpert Carba-R, reverse transcription quantitative
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