5 years ago

β-LACTA® test performance for detection of extended-spectrum-β-lactamase-producing Gram Negative Bacilli directly on bronchial aspirates samples: A validation study

Incidence of Extended Spectrum β-Lactamase-producing Gram Negative Bacilli (ESBL-P-GNB)-related infections is worryingly increasing worldwide. ESBL-P-GNB detection directly on bronchial aspirate samples (BAS) performed for suspected pneumonia may help save empirical carbapenems. Our objectives were to optimize β-LACTA® test (BLT) realization and evaluate BLT performance for ESBL-P-GNB detection directly on BAS. Methods 1) BLT technical optimization using BAS of different matrix types spiked with increasing concentrations of CTX-M-15-producing Klebsiella pneumoniae; 2) in vitro validation of BLT diagnostic performance on 17 ESBL enzymes, belonging to CTX-M, SHV, TEM, OXA, GES, VEB, and PER groups; 3) clinical validation of BLT performance on 126 BAS prospectively collected from 7 Intensive Care Units. Results After optimization, BLT detected with 100% sensitivity the presence of CTX-M-15-producing K. pneumoniae spiked in sterile BAS since inoculums providing ≥2 GNB/field upon Microscopic Gram Staining Examination (MGSE). The BLT detected accurately the 17 ESBLs tested at 106 CFU/mL and all ESBLs except P. aeruginosa-related OXA-14 at 104 CFU/mL. Among the 126 BAS of the validation cohort, 21 (17%) gave positive BLT (10 in BAS positive and 11 in BAS negative upon MGSE). All BLT-positive BAS grew with ESBL-P-GNB, including 5 hyper-L2-producing Stenotrophomonas maltophilia strains. BLT detected ESBL-P-GNB directly on clinical BAS positive for GNB on MGSE and/or growing with ≥104 CFU/mL with 100% sensitivity, specificity, positive and negative predictive values. Conclusions BLT is an accurate tool for ESBL-P-GNB detection directly on BAS. Further studies are needed to evaluate the impact of BLT-guided early antimicrobial de-escalation strategies.

Publisher URL: www.sciencedirect.com/science

DOI: S1198743X17304147

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