Objectives: To evaluate the biochemical Rapid ESBL NP ® (Liofilchem, Italy) for the rapid detection of extended-spectrum ß-lactamases (ESBL) in Enterobacterales.Methods: A total of 100 clinical Gram-negative strains (40 ESBL producers with or without cephalosporinase, 43 carbapenemase producers with or without additional ESBL, eight AmpCtype producers, six penicillinase producers and three non-β-lactamase producers) were tested using this colorimetric technique. Results:The overall sensitivity and specificity of the test were found to be 93.9% and 98.5%, respectively. This test is rapid (turn-around-time of 40-45 min), easy to perform, and reliable for identification of ESBL producers. Conclusion:The Rapid ESBL NP ® test allows differentiation between ESBL producers on one hand, and non ESBL-producers or isolates expressing combined mechanisms of resistance on the other hand.

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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 Acinetobacter baumannii. Here, we evaluated the industrial version of this test, the RapidResa Polymyxin Acinetobacter NP® test (Liofilchem, Italy). A well-characterized panel of 68 clinical A. baumannii strains (36 polymyxin-susceptible, 26 polymyxin-resistant A. baumannii, and 6 colistin-heteroresistant isolates) of worldwide origin was tested. All the colistin-susceptible A. baumannii isolates gave negative results according to the RapidResa Polymyxin Acinetobacter NP® test, except for a single isolate that gave a false-positive result. Out of the 26 colistin-resistant A. baumannii strains, 25 were correctly identified as colistin resistant using the RapidResa Polymyxin Acinetobacter NP® test. Only a single colistin-resistant A. baumannii 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 A. baumannii. The RapidResa Polymyxin Acinetobacter NP® test allows a rapid differentiation between polymyxin-susceptible and -resistant A. baumannii isolates, which may contribute to optimization of the use of polymyxins for treating infections due to multidrug-resistant A. baumannii.