MALDI-TOF lipidomics rapidly detects modification of 2-hydroxymyristate lipid A, a potential virulence trait in <i>Enterobacter bugandensis</i>
Bibliographic record
Abstract
ABSTRACT Enterobacter cloacae complex (ECC) comprises numerous species that can be difficult to identify. Among these species, Enterobacter bugandensis is recognized as a threat in neonatal intensive care units due to its involvement in septic shock. A potential virulence factor responsible for its virulence is the modification of the lipid A of the lipopolysaccharide (LPS). This modification corresponds to a hydroxylation of the myristate component of lipid A. A collection of 168 ECC, including 10 E. bugandensis and one isolate involved in fatal septic shock in the neonatal intensive care unit, were tested for the presence of 2-hydroxymyristate. All isolates were sequenced to determine the genetic diversity of this collection and detect the presence of the lpxO gene responsible for this hydroxylation. matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) analysis revealed that only a fraction (4/11) of E. bugandensis were able to modify their lipid A, which correlates with the presence of the lpxO gene. Genomic analysis of E. bugandensis revealed that only half of the genomes carried the lpxO gene. Lpxo-negative isolates exhibited a deletion of 1,094 bp encompassing the lpxO gene. Lipid A analysis also revealed that hydroxylation of myristate was not specific to E. bugandensis since this modification was systematically found in several species including Enterobacter chengduensis , Enterobacter chuandaensis, or Enterobacter cloacae subsp cloacae. Here, we provide a simple detection test allowing the rapid identification of hydroxymyristate of lipid A involved in the virulence of E. bugandensis . Rapid identification of lipid A modification might help clinicians to adapt procedures when an Enterobacter spp. is identified in newborns. IMPORTANCE Enterobacter bugandensis is now recognized as a potential threat in neonatal wards due to its ability to survive in incubators and its virulence properties. Its increased virulence is linked to the addition of 2-hydroxymyristate on lipid A, resulting from the action of the LpxO enzyme. Here, we proposed a rapid and simple assay to decipher the presence of 2-hydroxymyristate on lipid A directly from the bacterial colony. This assay can be performed easily on MALDI-TOF routine machine using a commercial kit (MBT Lipid Xtract Kit, Bruker Daltonic). This test can accurately detect the 2-hydroxymyristate on lipid A of lpxO-positive ECC isolates, including E. bugandensis . In neonate wards, newborns are now screened for ECC carriage. Accordingly, the MALDIxin test might help clinicians detect the presence of lpxO-positive E. bugandensis, which can be considered a risk factor for the newborn, and implement measures to avoid potentially fatal septicemia.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".