RESUMO
AIM: To design and assess a novel protocol that employs isothermal titration calorimetry (ITC) for rapid detection of extended-spectrum ß-lactamase (ESBL)-producers in clinical pathogens. METHODS AND RESULTS: A total of 69 clinical Enterobacteriaceae isolates were examined in the new ESBL-ITC test by examining the heat profiles associated with enzyme hydrolysis of different substrates (imipenem, cefotaxime and clavulanic acid). The presence of ß-lactamase genes in the bacteria tested was confirmed by PCR and DNA sequencing. Comparative analysis between ESBL-ITC and conventional minimum inhibitory concentrations (MIC)/combined disk method (CDM) showed high agreement between the two assays. However, the ESBL-ITC test had a remarkable advantage of providing testing result within 1 h, in comparison to the 32-48 h required by MIC/CDM. CONCLUSIONS: The ESBL-ITC test developed in this work offers a new option for rapid and accurate detection of ESBL-producers. SIGNIFICANCE AND IMPACT OF THE STUDY: Timely detection of ESBL-producers is vital to guide the decision-making process in clinical treatment as well as in hospital-infection control. The new ESBL-ITC test provides a rapid phenotypic assay that can be further adapted for clinical diagnosis of ESBL-producing pathogens.