The treatment options for infections caused by carbapenem-resistant Enterobacterales are scarce and the development of new antibiotics is an urgent necessity. Imipenem/relebactam (IPR) has been recently introduced for treating severe infections related to multidrug-resistant bacteria. However, IPR resistance has already been reported in Enterobacterales, thus its rapid detection may be interesting for clinical decision-making. The aim of the study was to develop a rapid and accurate test, namely the Rapid IPR Nordmann Poirel (NP) test, for the identification of IPR resistance among multidrug-resistant Enterobacterales.
The Rapid IPR NP test is based on the detection of glucose metabolization because of bacterial growth in the presence of IPR. Bacterial growth is visually detectable by a colour change of the red phenol pH indicator, turning from red to yellow subsequent to the acidification of the medium upon bacterial growth. Cultures of a total of 94 Enterobacterales isolates were selected for evaluating the performance of the Rapid IPR NP test.
The sensitivity and specificity of the test were found to be 95.2% (95.2%, CI 84.2-98.7%) and 100% (100%, CI 93.1-100%), respectively. All the results were obtained within 3 hours incubation time at 35°C ± 2°C, which is a gain of time of at least 15 hours when compared with currently used antimicrobial susceptibility. The test showed two very major errors corresponding to OXA-48-producing Klebsiella pneumoniae isolates with MICs of IPR at 8 mg/L.
The Rapid IPR NP test is simple to perform and interpret, and shows excellent performances. Thus, it may suitable for implementation in clinical microbiology routine laboratories.