Disk Diffusion Assay for Oritavancin Using Polysorbate 80
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Solution Overview
Problem
Current antimicrobial susceptibility testing methods for oritavancin, such as disk diffusion assays, face challenges due to non-specific binding of the drug to plastic and glass surfaces, leading to inaccurate potency measurements, and existing methods like broth microdilution are technically cumbersome, necessitating a simpler and accurate method for determining bacterial susceptibility.
Innovation Solution
A disk diffusion assay using paper disks impregnated with a solution of oritavancin and polysorbate 80, with specific concentrations and storage conditions, is developed to enhance diffusion and accuracy, ensuring zone diameters meet the minimum requirements recommended by the Clinical Laboratory Standards Institute (CLSI) for bacterial susceptibility testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a disk diffusion assay is used for oritavancin testing, then the simplicity and wide usage of the method is maintained, but the non-specific binding of oritavancin to plastic and glass surfaces leads to inaccurate potency measurements
Solution Approach 1:
The patent introduces an intermediary substance (surfactant such as polysorbate 80, Tween 80, or Triton X-100) to the disk diffusion assay system. This surfactant acts as a mediator that prevents oritavancin from binding non-specifically to the plastic disk and glass surfaces of the testing apparatus, thereby eliminating the source of measurement inaccuracy while preserving the simplicity of the disk diffusion method
Solution Approach 2:
The patent modifies the chemical parameters of the testing system by incorporating surfactants at specific concentrations (0.002-10% v/v) into the assay. This parameter change alters the surface properties of the testing apparatus and the behavior of oritavancin in the system, preventing non-specific binding and enabling accurate potency measurements through the simple disk diffusion approach
2Measurement precision
If broth microdilution method is used to avoid non-specific binding, then accurate MIC determination is achieved, but the method becomes technically cumbersome
Solution Approach 1:
The patent applies the same intermediary principle to simplify the complex broth microdilution method. By incorporating surfactants into the broth microdilution system, the patent eliminates the need for complex procedural steps while maintaining accurate MIC determination, thus reducing device complexity without sacrificing measurement precision
Solution Approach 2:
The patent modifies the broth microdilution system by changing the chemical parameters (adding surfactants at 0.002-10% concentrations), which simplifies the overall testing procedure while preserving the accuracy of MIC determination, thereby resolving the contradiction between accuracy and complexity
3Ease of operation
If standard disk diffusion conditions are used for oritavancin, then the simplicity of the method is maintained, but the zone diameters do not meet the minimum CLSI requirements of ≥15 mm
Solution Approach 1:
The patent introduces surfactant as an intermediary that improves the diffusion characteristics of oritavancin in the agar medium. This intermediary substance prevents surface binding and promotes uniform diffusion, resulting in zone diameters that meet the CLSI minimum requirement of ≥15 mm while maintaining the simplicity of the disk diffusion assay
Solution Approach 2:
The patent changes the chemical parameters of the disk diffusion system by incorporating surfactants at optimized concentrations (0.002-10% v/v). This parameter modification enhances the diffusion properties of oritavancin, ensuring that zone diameters meet the required precision standards (≥15 mm) without compromising the ease of operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed method achieves zone diameters of ≥15 mm for methicillin-susceptible Staphylococcus aureus, correlating with broth microdilution minimal inhibitory concentration (MIC) results, providing a reliable and simplified approach for determining bacterial susceptibility to oritavancin.
Implementation Method 1
inclusion of 0.002% polysorbate-80 (P80) during BMD MIC testing minimizes loss of oritavancin due to non-specific binding
Implementation Method 2
slow diffusion of oritavancin in agar results in zones of clearance (zone diameters)
Data Source
Figure 1~2
Figure 3
AI summary
The present invention is directed to a disk diffusion assay for determining susceptibility of bacteria to a glycopeptide antibiotic. The assay includes improvements over conventional assays due to the inclusion of polysorbate 80 and Span 80 in the antibacterial solution used to impregnate paper disks used in the assay.