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Aim We validated two methods for the direct identification of bacteria from positive BACTEC blood culture bottles with the MALDI-TOF technique. Methods 872 blood culture bottles positive with the BACTEC system (BD) were tested. For MALDI-TOF identification two specimen collection and blood cell extraction methods were tested [Method 1: Vacutainer serum seperator tubes (BD); Method 2: MALDI Sepsityper Solutions (Bruker)]. For both methods, bacterial proteins were extracted by the formic acid/ acetonitrile standard method and measured in a MALDI-TOF spectrometer of the FLEX series (Bruker Daltonics). Identification results were compared to routine biochemical methods (VITEK 2, api-system, BioMe´rieux). Results Of 789 blood cultures tested with Method 1, 636 (80%) showed a valid (score value > 1,7) identification result with the MALDI-TOF. Of these valid samples, 630 (99%) were correctly identified to species level in comparison to routine biochemical methods. For Method 2, 83 blood cultures were tested, 75 (80%) were considered as valid, 99% showed a correct result to species level. Discussion The MALDI-TOF technique proved to be a fast and reliable method for the detection of bacteria directly from BACTEC blood culture bottles. Results are available 1–2 days earlier in comparison to conventional methods. |
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