ABSTRACT
INTRODUCTION: Here, we propose a novel modified Carba NP test for detecting KPC-producing Enterobacterales using imipenem/relebactam. MATERIAL AND METHODS: The test performance was evaluated in a random selection of 160 previously molecularly characterized clinical isolates carrying the 110 blaKPC, 1 blaGES, 12 blaVIM, 4 blaIMP, 3 blaNDM and 42 blaOXA-48-like genes. The proposed method relies on the detection of imipenem hydrolysis in an imipenem/relebactam antibiotic solution and subsequent visual interpretation by color change. RESULTS: All class A producing Enterobacterales (111/111) were detected using imipenem/relebactam as no visual appreciation of color change was perceived due to a nule hydrolysis of imipenem in the antibiotic solution. Overall, the assay showed 100% sensitivity (111/111) and specificity (69/69) for detecting class A KPC-producing Enterobacterales. DISCUSSION: The biochemical assay provides very reliable results for detecting KPC-producing Enterobacterales, with a turnaround time of less than 1 hour, minimum handling and no specialized equipment required.
Subject(s)
Gammaproteobacteria , Imipenem/pharmacology , Anti-Bacterial Agents/pharmacology , Azabicyclo CompoundsABSTRACT
INTRODUCTION: Here, we propose a novel modified Carba NP test for detecting KPC-producing Enterobacterales using imipenem/relebactam. MATERIAL AND METHODS: The test performance was evaluated in a random selection of 160 previously molecularly characterized clinical isolates carrying the 110 blaKPC, 1 blaGES, 12 blaVIM, 4 blaIMP, 3 blaNDM and 42 blaOXA-48-like genes. The proposed method relies on the detection of imipenem hydrolysis in an imipenem/relebactam antibiotic solution and subsequent visual interpretation by color change. RESULTS: All class A producing Enterobacterales (111/111) were detected using imipenem/relebactam as no visual appreciation of color change was perceived due to a nule hydrolysis of imipenem in the antibiotic solution. Overall, the assay showed 100% sensitivity (111/111) and specificity (69/69) for detecting class A KPC-producing Enterobacterales. DISCUSSION: The biochemical assay provides very reliable results for detecting KPC-producing Enterobacterales, with a turnaround time of less than 1 hour, minimum handling and no specialized equipment required.
ABSTRACT
Objectives: Development of an automated MALDI-TOF MS-based method for the rapid, direct detection of carbapenemase-producing Enterobacteriaceae in clinical urine samples within 90â min of sample reception. Methods: A total of 3041 urine samples were processed by flow cytometry, and a cut-off value of ≥1.5 × 10 5 bacteria/mL was used to select samples for the study. Following these criteria, 608 samples were selected for direct bacterial identification. Detection of carbapenemase activity by MALDI-TOF MS analysis was only performed after reliable direct identification of Gram-negative bacilli. A novel protocol was developed for extracting bacteria from urine samples by using the Sepsityper Kit (Bruker Daltonik, Germany). Carbapenem resistance was detected with imipenem as an antibiotic marker and the results were automatically interpreted using the STAR-BL module of MALDI-TOF Biotyper Compass software (Bruker Daltonik, Germany). Results: The MALDI-TOF MS-based assay yielded direct reliable identification of 91% (503/553) of the samples. The assay showed 100% sensitivity (30/30) and specificity (454/454) for detecting carbapenemase activity within 90â min of sample reception. Isolates included in the study were further characterized by PCR and sequencing, and bla OXA-48 was detected from all isolates that tested positive in the MALDI-TOF MS-based resistance assay. Conclusions: The proposed protocol for the direct analysis of urine samples by MALDI-TOF MS is suitable for use in clinical laboratories to identify bacteria and detect carbapenemase activity, thus saving at least 24-48â h relative to current routine methods.
