Direct Rapid Identification of Bacteria From Positive Blood Cultures Using the Bruker MALDI Biotyper and Serum Separator Tubes
Bibliographic record
Abstract
Background. Direct rapid identification of microorganisms from positive blood culture bottles would decrease the time to targeted antimicrobial therapy and improve patient care. The Bruker Sepsityper kit is commercially available but has multiple steps and takes about 40 minutes to process specimens. We evaluated an in-house method to rapidly identify bacteria directly from positive blood culture medium using the Bruker MALDI Biotyper and serum separator tubes (SST). Methods. Positive blood culture isolates from 165 patients were included in our study. When a resin-based BacT/Alert (bioMérieux) blood culture bottle was flagged positive, 5 mL of the broth was transferred to a 5 mL serum separator tube and centrifuged at 4000 rpm for 5 minutes. The supernatant was aspirated without disrupting the pellet of bacteria present at the surface of the polymeric gel. A sterile wooden stick was then used to spot the pellet on to the stainless steel target. The bacteria were then allowed to dry, then overlaid with 1 µL of α-cyano-4-hydroxycinnamic acid (HCCA) matrix, and analyzed using the MALDI-TOF mass spectrometer (MALDI Biotyper with FlexControl software; Bruker Daltonics). The positive blood culture bottle was also routinely processed to identify the bacteria by conventional methods. Results. Of the 165 specimens tested by the SST method, 124 were Gram-negative, 34 were Gram positive, and 7 were anaerobes. Overall, correct identification to the genus and species levels was obtained in 156 of 165 (95%) and 153 of 165 (92.7%) blood culture broths, respectively. Gram-negative organisms were identified correctly to the genus level in 120 of 124 (96.7%) and to the species level in 118 of 124 (95.1%) specimens. Gram positive organisms were identified correctly to the genus level in 30 of 34 (88.2%) and to the species level in 29 of 34 (85.2%) specimens. Six of the 7 (85.7%) anaerobes tested were identified correctly to the genus and species levels. The use of the SST method for direct identification of organisms was simple and had an average turnaround time of 15 minutes. Conclusion. Utilizing MALDI-TOF MS with the SST method is a promising tool for the direct identification of organisms from positive blood culture bottles. Disclosures. All authors: No reported disclosures.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".