There are several approaches available for purifying microorganisms prior to matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis. In the present study, rapid BACpro® II (Nittobo Medical Co., Ltd., Tokyo, Japan), a new application, has been compared with Sepsityper® kit (Bruker Daltonics, Billerica, USA) and an in-house method. Samples were also tested with two modules, standard and Sepsityper®, identified in the Bruker MALDI-TOF MS. The bottles having monomicrobial growth were included in the study according to Gram staining results. In total, two hundred blood culture bottles were included but there was no growth in one of the subcultures so 199 blood culture bottles were studied prospectively. With the standard MALDI-TOF MS analysis, rapid BACpro® II could successfully identify microorganisms in 174/199 (87.4%) of the bottles where Sepsityper® kit and in-house method were successful in 136/199 (68.3%) and 114/199 (57.3%), respectively. When the MALDI-TOF MS data were analysed by Sepsityper® module, the identification rates were increased to 94.4%, 82.1% and 69.8% (p < 0.001), respectively. In the Sepsityper® module, 72/73 (98.6%) of Gram-negative and 97/106 (91.5%) of Grampositive microorganisms were detected by rapid BACpro® II method. The present study shows that rapid BACpro® II is a reliable preparation procedure and has higher rates of identification compared with Sepsityper® kit and in-house method. The use of the Sepsityper® module in blood cultures increases the chance of identification for all three methods studied.
Blood stream infection (BSI) is related to high mortality and morbidity. Early antimicrobial therapy is crucial in treating patients with BSI. The most common Gram-negative bacteria causing BSI is Escherichia coli. Targeted effective treatment of patients with BSI is only possible if it is based on antibiotic susceptibility testing (AST) data after blood culture positivity. However, there are very few methods available for rapid phenotypic AST and the fastest method takes 4 h. Here we analyzed the performance of a 30 min ultra-rapid method for AST of E. coli directly from positive blood cultures (BC). In total, 51 positive BC with E. coli were studied, and we evaluated the ultra-rapid method directly on positive BC as well as on E. coli colonies cultured on agar plates. The results obtained by the new method were compared with disk diffusion.The method provided accurate AST result in 30 min to Ciprofloxacin and Gentamicin for 92% and 84% of the positive BC samples, respectively. For E. coli isolates retrieved from agar plates, 86% and 96% of the AST results were accurate for Ciprofloxacin and Gentamicin, respectively, after 30 min of assay time. When time to result was modulated in-silico from 30 to 60 minutes for the agar plate samples, accuracy of AST results went up to 92% for Ciprofloxacin and to 100% for Gentamicin.The present study shows that the method is reliable and delivers ultra-rapid AST data in 30 minutes directly from positive BC and as well as from agar plates.
Early effective antimicrobial treatment has been shown to be crucial for improving the outcome of bloodstream infections (BSI) and sepsis. In combination with the rise of antibiotic resistance, this calls for accelerated methods for antibiotic susceptibility testing (AST) for effective treatment of BSI.
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