GB/T 40672-2021 in English
VALIDClinical laboratory testing—Criteria for acceptable lots of dehydrated Mueller-Hinton agar and broth for antimicrobial susceptibility testing
- Issued on:2021-10-11
- Implemented on:2023-05-01
- File Format:PDF
- Delivery:Via email within 5 business days
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《GB/T 40672-2021临床实验室检验 抗菌剂敏感试验脱水MH琼脂和肉汤可接受批标准》由TC136（全国医用临床检验实验室和体外诊断系统标准化技术委员会）归口，主管部门为国家药品监督管理局。
Introduction
Analysis of the core content of the standard
GB/T40672-2021 is equivalent to ISO/TS16782:2016, and has established a strict performance evaluation system for dehydrated MH agar (dMHA) and dehydrated MH broth (dMHB). The standard ensures the comparability and accuracy of antimicrobial sensitivity test results by standardizing culture medium composition, physical and chemical properties, and quality control schemes.
Comparison of key technical requirements
| Indicators | Dehydrated MH broth (dMHB) | Dehydrated MH agar (dMHA) |
|---|---|---|
| Basic ingredients | Beef extract 2g/L+Casein acid digest 17.5g/L+Starch 1.5g/L | Same basic ingredients+Agar 17g/L |
| pH range | 7.2-7.4（25℃） | 7.2-7.4（25℃） |
| Cation limit | Ca²⁺≤25mg/L, Mg²⁺≤12.5mg/L, Zn²⁺＜3mg/L, Mn²⁺＜8mg/L | Same as left, the inhibition ring of Pseudomonas aeruginosa must meet the standard |
| Key quality control strains | Five strains of Pseudomonas aeruginosa WDCM00025 and Escherichia coli WDCM00013 | Six strains of Staphylococcus aureus WDCM00034 |
| Special adjustments | NaCl (20g/L) must be added for the oxacillin test; Ca²⁺ (50mg/L) must be supplemented for daptomycin | Fascinating bacteria require the addition of blood components |
In-depth analysis of key quality control points
1. Technical principles of cation control
The standard strictly limits the concentrations of calcium, magnesium, zinc, manganese and other ions, which is based on a large amount of research evidence:
- Zinc>3mg/L can lead to false resistance to carbapenems (abnormally elevated imipenem MIC)
- Manganese>8mg/L affects the drug sensitivity results of glycylcyclines (tigecycline)
- Insufficient calcium and magnesium ions can cause the MIC values of aminoglycosides and quinolones to deviate from the true values
2. Quality control strain selection logic
The quality control strain combination required by the standard has a clear functional positioning:
- Pseudomonas aeruginosa WDCM00025: Verify the performance of aminoglycosides/carbapenems
- Escherichia coli WDCM00013: Monitor the accuracy of tetracyclines/quinolones
- Enterococcus faecalis WDCM00087: Detect the content of thymidine deoxynucleoside (≤0.03mg/L)
Recommendations for the implementation of the standard
Laboratory operating specifications
Key points of culture medium preparation:
- Use inductively coupled plasma mass spectrometry (ICP-MS) to verify the cation content
- The thickness of agar is strictly controlled at 4±0.5mm (90mm plate requires 25±2mL culture medium)
- After sterilization, the MH broth needs to be tested for sediment and transparency.
Optimization of quality control frequency
A three-level quality control strategy is recommended:
| Level | Content | Frequency |
|---|---|---|
| Batch acceptance | Full-item testing (physical and chemical + 6 types of quality control bacteria) | Every production batch |
| Daily monitoring | Basic verification of 2 strains of E. coli and Staphylococcus aureus | Weekly/batch |
| Trend analysis | MIC/moving average of inhibition zone diameter | Monthly statistics |
Background of technological evolution
This standard integrates CLSI The core content of M6-A2 and M32-P, the main technical breakthroughs include:
- Establish quantifiable cation limits (traditional standards only have qualitative requirements)
- Clear the WDCM/ATCC dual numbering system for quality control strains
- Introduce EUCAST and CLSI dual quality control ranges
Note: The standard specifically emphasizes the need to regularly check the CLSI M100 and EUCAST official website to update the quality control range.
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