575. Optimization of a Nitrocefin-Based Rapid Test for the Detection of the Cefazolin Inoculum Effect (CzIE) in Methicillin-Susceptible <i>Staphylococcus aureu</i>s
Notice bibliographique
Résumé
Abstract Background The cefazolin (Cz) inoculum effect, defined as a Cz MIC ≥16 µg/mL at 107 CFU/mL in MSSA isolates, has been associated with poor outcomes in adult patients with MSSA bacteremia and pediatric patients with osteomyelitis. Broth microdilution at high inoculum is the gold standard for the detection of the CzIE, but this method is time and labor-intensive. We developed a nitrocefin-based rapid test that can identify the CzIE among MSSA(Figure 1). However, the original protocol for this rapid test includes the use of ampicillin in solution, which is difficult to prepare and unstable once reconstituted. In this study, we aimed to show that simple elution from ampicillin disks available in the typical clinical microbiology lab performs as well as an ampicillin powder-based assay.Figure 1.Original Protocol Nitrocefin Rapid Test Original Protocol for the performance of the Nitrocefin-based rapid test as published by Rincon et at (Rincon et al, JCM, 2021) Methods We included 107 unique MSSA bloodstream isolates which had been previously characterized (Dingle et al., JCM, 2022). The CzIE was determined using gold standard broth microdilution at high inoculum (107 CFU/mL). The published protocol of the nitrocefin test (Rincon et al., JCM, 2021) was modified as follows (Figure 2): instead of adding ampicillin from powder to BHI broth (150 ug/mL), ampicillin disks (10 ug) of 2 different brands (Oxoid and BD) were added to 1 mL of BHI broth of 2 different brands (Oxoid, BD) and incubated for 2 hours at room temperature with frequent shaking (Figure 3). The remaining steps of the protocol were not modified. The original protocol was used as control. Performance metrics were calculated for the complete data set.Figure 2.Modification to Nitrocefin-based rapid test protocol Modification of the Step 1 from the original protocol to include ampicillin disks instead of ampicillin from powder. Figure 3. Experiments and Controls. 2 different brands of BHI broth and 2 different brands of ampicillin disks(10 ug) were compared to the use of ampicillin from powder to a final concentration of 150 ug/mL Results 51.4%(55/107) of the isolates were CzIE+ by reference broth microdilution at high inoculum. When using Oxoid BHI broth, the sensitivity and specificity of the test were 96.3% and 90.3% regardless of the ampicillin form (disk vs powder) or disk brand (Table 1). When using BD BHI broth, the sensitivity and specificity of the test were 69.1% and 94.2%, regardless of the ampicillin form or disk brand.Table 1.ResultsPerformance metrics of the Nitrocefin-based rapid test with the original protocol (Control A and Control B) and the modified protocol using ampicillin disks from 2 different brand (BD: Experiments C and D; Oxoid: Experiments E and F) as well as 2 different brands of BHI broth (BD: Control A, experiments C and E; Oxoid: Control B, experiments D and F) Conclusion The modification of the nitrocefin-based rapid to use ampicillin disks instead of ampicillin powder did not impact the accuracy of the tests as it was able to correctly detect the CzIE in isolates, regardless of the brand of ampicillin disk. Implementation of this test may contribute to therapeutic decisions in deep-seated MSSA infections. Disclosures Jennifer Dien Bard, PhD, Abbott Molecular: Grant/Research Support|BioMerieux: Advisor/Consultant|BioMerieux: Grant/Research Support|BioMerieux: Honoraria|Genetic Signature: Advisor/Consultant|Genetic Signature: Grant/Research Support|Luminex: Grant/Research Support|Salve: Stocks/Bonds|Thermo Fisher: Honoraria Lars Westblade, PhD, Accelerate Diagnostics, Inc.: Grant/Research Support|bioMerieux, Inc.: Grant/Research Support|Hardy Diagnostics: Grant/Research Support|Roche Molecular Systems, Inc.: Advisor/Consultant|Roche Molecular Systems, Inc.: Grant/Research Support|Selux Diagnostics, Inc.: Grant/Research Support|Shionogi, Inc.: Advisor/Consultant|Talis Biomedical: Advisor/Consultant William R. Miller, M.D., Merck: Grant/Research Support|UpToDate: Honoraria
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,003 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,002 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».