Detection of Heterogeneously Vancomycin Intermediate Resistant (hVISA) Staphylococcus aureus from Blood Stream Infections (BSI)
Bibliographic record
Abstract
Background: There is evidence that hetero-resistance may be associated with failure of vancomycin therapy. Most routine MIC testing methods used in diagnostic laboratories do not detect hVISA strains. There are few published Canadian studies using other methods for this purpose. Objective: To use the Macro E-test method and the Glycopeptide Resistance Detection (GRD) E-test (AB Biodisk, Sweden)to assess the prevalence of hVISA among the bacteremic isolates of S. aureus at a tertiary care centre in Canada. Methods: Ninety two isolates of S. aureus including 7 Methicillin Resistant S. aureus (MRSA) from BSI were tested by standard, Macro E-test and GRD methods. For the standard E-test, the organism was tested at 0.5 McFarland on Mueller Hinton (MH)Agar, and incubated for 24 hours at 35 °C. For Macro E-test, 100 μl of a 2.0 McFarland suspension was used on BHI Agar incubated for 48 hours at 35 °C. For GRD, 0.5 McFarland inoculum was tested on MH with 5% blood, incubated for 48 hours at 35 °C.A strain was defined as hVISA if it had an MIC of (>) 8 μg/ml for vancomycin and teicoplanin by Macro or GRD E-test. Results: All the isolates were sensitive to vancomycin and teicoplanin, when tested by the standard method. The MIC50 and MIC90 were: vancomycin 1.0 μg/ml and 1.5 μg/ml; teicoplanin 0.5 μg/ml and 0.75 μg/ml. Though hVISA was not detected among the 92 strains tested by Macro E-test method as per the defined criteria, some strains showed increased MICs (6.0 μg/ml). MIC50 and MIC90 were: vancomycin 3.0 μg/ml and 6.0 μg/ml; teicoplanin 3.0 μg/ml and 6.0 μg/ml.The MIC50 and MIC90 by GRD were: vancomycin 1.0 μg/ml and 1.5 μg/ml; teicoplanin 2.0 μg/ml and 3.0 μg/ml. Conclusions: Routine screening is not warranted as no hVISA isolates were detected. Some strains had a Macro E-test MIC of 6.0 μg/ml for both glycopeptides. This suggests that periodic screening of S. aureus isolates from BSI may be useful to check for the occurrence of hVISA.
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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 | 0.001 |
| 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".