SN/T 5228.3-2019 in English
VALIDRapid detection of pathogens in export food-MALDI-TOF MS method- Part 3: Staphylococcus aureus
- Issued on:2019-12-27
- Implemented on:2020-07-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
$97.00
Introduction
Background and evolution of standard technology
With the continuous improvement of food safety requirements in international trade, traditional microbial detection methods (such as culture methods) can no longer meet the needs of rapid customs clearance of exported food. MALDI-TOF MS technology, with its high-throughput characteristics of matrix-assisted laser desorption ionization time-of-flight mass spectrometer, shortens the detection cycle from 3-5 days of traditional methods to within 24 hours, becoming an internationally recognized gold standard for rapid microbial identification.
Analysis of core detection process
| Steps | Direct smearing method | Formic acid extraction method |
|---|---|---|
| Pretreatment time | 5 minutes | 45 minutes |
| Sensitivity | Single colony level | Subcellular level |
| Applicable scenarios | Preliminary screening | Difficult samples |
Key mass spectrometry parameter settings
The standard clearly stipulates linear operation mode, the following conditions must be maintained:
- Laser frequency: 60.0 Hz
- Ion source accelerating voltage: 20 kV
- Mass range: 2000-20000 Da
Actual cases show that when using BTS standards for calibration, the mass-to-charge ratio error must be controlled within ±0.03%, otherwise it may lead to identification deviations of the characteristic peaks of Staphylococcus aureus (such as m/z 4420, 5095).
Results Determination Grading Standards
| Score Range | Determination Level | Handling Suggestions |
|---|---|---|
| ≥2.300 | Species Level Credibility | Direct Report |
| 2.000-2.299 | Genus Level Credibility | Supplementary Biochemical Tests |
| 1.700-1.999 | Suspicious Result | Retest |
Implementation Suggestions and Precautions
- Biosafety: All operations must be performed in a BSL-2 laboratory, and waste must be sterilized at 121°C for 30 minutes
- Matrix preparation: CHCA solution must be replaced if precipitation occurs to avoid uneven crystallization affecting ionization efficiency
- Mass spectrometer maintenance: Escherichia coli ATCC 8739 must be used to verify system performance before daily testing
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