4 years ago

Multicenter Evaluation of the Modified Carbapenem Inactivation Method and the Carba NP for Detection of Carbapenemase-Producing Pseudomonas aeruginosa and Acinetobacter baumannii.

Brandi M Limbago, Virginia M Pierce, Brian B Yoo, Lars F Westblade, Angella Charnot-Katsikas, J Kristie Johnson, Karen Anderson, David R Lonsway, Sanchita Das, Patricia J Simner, Darcie E Roe-Carpenter, Zabrina C Lockett, Stephen G Jenkins, William B Brasso, April M Bobenchik
The purpose of this study was to develop the modified Carbapenem Inactivation Method (mCIM) for the detection of carbapenemase-producing (CP) Pseudomonas aeruginosa (PA) and Acinetobacter baumannii (AB) and perform a multicenter evaluation of the mCIM and Carba NP tests for these non-fermenters. Thirty P. aeruginosa and 30 A. baumannii isolates previously characterized by whole genome sequencing from the CDC-FDA Antibiotic Resistance Isolate Bank were evaluated, including carbapenemase-producers (CP; Ambler Class A, B, and D), non-carbapenemase-producing (non-CP) carbapenem-resistant isolates, and carbapenem-susceptible isolates. Initial comparison of a 1 μl versus 10 μl loop inoculum for the mCIM was performed by two testing sites and showed that 10 μl was required for reliable detection of carbapenemase production among PA and AB. Ten testing sites then evaluated the mCIM using a 10 μl loop inoculum. Overall, the mean sensitivity and specificity of the mCIM for detection of CP-PA across all ten sites were 98.0% (95% CI: 94.3-99.6; range: 86.7-100) and 95% (95% CI: 89.8-97.7; range: 93.3-100), whereas the mean sensitivity and specificity among CP-AB were 79.8% (95% CI: 74.0-84.9; range: 36.3-95.7) and 52.9% (95% CI: 40.6- 64.9; range: 28.6-100), respectively. At three sites that evaluated the performance of the Carba NP using the same set of isolates, the mean sensitivity and specificity of the Carba NP were 97.8% (95% CI: 88.2-99.9; range: 93.3-100) and 97.8% (95% CI: 88.2-99.9; range: 93.3-100) for PA and 18.8% (95%CI: 10.4-30.1; range: 8.7-26.1) and 100% (95% CI: 83.9-100; range: 100) for AB. Overall, we found both the mCIM and the Carba NP to be accurate for detection of carbapenemases among PA and less reliable for use with AB isolates.

Publisher URL: http://doi.org/10.1128/JCM.01369-17

DOI: 10.1128/JCM.01369-17

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