RapidResa Polymyxin <i>Acinetobacter</i> NP^® Test for Rapid Detection of Polymyxin Resistance in <i>Acinetobacter baumannii</i>

• Main Authors: Maxime Bouvier, Mustafa Sadek, Stefano Pomponio, Fernando D’Emidio, Laurent Poirel, Patrice Nordmann
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Antibiotics
• Subjects: colistin; <i>Acinetobacter</i>; susceptibility testing; diagnostic test
• Online Access: https://www.mdpi.com/2079-6382/10/5/558

A homemade and culture-based test, relying on the visual detection of the reduction of the resazurin reagent (a cell viability indicator), has been developed for the rapid detection of polymyxin resistance in <i>Acinetobacter baumannii</i>. Here, we evaluated the industrial version of this test, the RapidResa Polymyxin <i>Acinetobacter</i> NP^® test (Liofilchem, Italy). A well-characterized panel of 68 clinical <i>A. baumannii</i> strains (36 polymyxin-susceptible, 26 polymyxin-resistant <i>A. baumannii</i>, and 6 colistin-heteroresistant isolates) of worldwide origin was tested. All the colistin-susceptible <i>A. baumannii</i> isolates gave negative results according to the RapidResa Polymyxin <i>Acinetobacter</i> NP^® test, except for a single isolate that gave a false-positive result. Out of the 26 colistin-resistant <i>A. baumannii</i> strains, 25 were correctly identified as colistin resistant using the RapidResa Polymyxin <i>Acinetobacter</i> NP^® test. Only a single colistin-resistant <i>A. baumannii</i> strain gave a false-negative result. Additionally, the six colistin-heteroresistant isolates tested gave positive results. Altogether, the sensitivity and the specificity of the test were found to be 96% and 97%, respectively. The turn-around-time of this easy-to-perform test was 3-4h, which showed excellent reliability for identification of polymyxin resistance in <i>A. baumannii</i>. The RapidResa Polymyxin <i>Acinetobacter</i> NP^® test allows a rapid differentiation between polymyxin-susceptible and -resistant <i>A. baumannii</i> isolates, which may contribute to optimization of the use of polymyxins for treating infections due to multidrug-resistant <i>A. baumannii.</i>