Current evidence suggests that early diagnosis of sepsis and timely detection of antimicrobial resistance are crucial to improve mortality rates among patients. The aim of this study was to evaluate a rapid method for the identification of Gram-negative bacteria from positive blood cultures (BCs), combined with the detection of extended spectrum β-lactamases (ESβL) and carbapenemases production, by means of MALDI-TOF MS analysis.
During the study, all BCs positive for Gram-negative rods were selected. Starting from bacterial pellet obtained directly from BC broths, species identification and hydrolysis assays were achieved through MALDI-TOF MS (Bruker). In particular, we performed a hydrolysis assays of cefotaxime (CTX) and ertapenem (ERT) for the rapid detection of resistance due to ESβL and carbapenemases, respectively. These results were compared to the routine workflow, including BCs subcultures and confirmation phenotypic methods. Finally, a comparison of the turn-around-time (TAT) between the two protocols was conducted.
Overall, 185 BCs positive forEnterobacteriaceae were collected. In term of species identification, we observed a concordance of 95.9% comparing MALDI-TOF MS results to the subculture-based method. The sensitivity and specificity for CTX hydrolysis assay were 91.1% and 92%, respectively; ERT hydrolysis assay showed a sensitivity of 96.2% and a specificity of 99.2%. The TAT of the proposed MALDI TOF MS-based protocol was significantly lower compared to the routine workflow (p < 0.0001).
The proposed protocol can provide a reliable bacterial identification and data concerning β-lactams resistance in only 3 hours, positively improving patient’s management in term of antimicrobial stewardship.
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