An improved in-house lysis-filtration protocol for bacterial identification from positive blood culture bottles with high identification rates by MALDI-TOF MS

Performance of the in-house protocol was evaluated using a total of 117 monomicrobial cases of positive blood culture. Medium from blood culture bottles was pretreated by the in-house protocol or the commercial kit, and isolated cells were subjected to direct identification by mass spectrometry fingerprinting in parallel with conventional subculturing for reference identification. The overall MALDI-TOF MS-based identification rates with score > 1.7 and > 2.0 obtained using the in-house protocol were 99.2% and 85.5%, respectively, whereas those obtained using the Sepsityper Kit were 85.4% and 61.5%, respectively. For Gram-positive cases, the in-house protocol yielded scores >1.7 and > 2.0 at 98.5% and 76.1%, respectively, whereas the commercial kit yielded these scores at 76.1% and 43.3%, respectively. Although these are preliminary results, these values suggest that this easy lysis-filtration protocol deserves assessment in a larger-scale test.