SN/T 5228.6-2019 in English
VALIDRapid detection of pathogens in export food-MALDI-TOF MS method- Part 6: Bacillus cereus
- Issued on:2019-12-27
- Implemented on:2020-07-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
$97.00
Introduction
Technical background and significance of the standard
As the sixth part of the SN/T 5228 series, this standard establishes a rapid detection system based on MALDI-TOF MS technology for Bacillus cereus, a foodborne pathogen. Compared with traditional culture methods, this technology has three advantages: short detection cycle (within 24 hours), high throughput and high specificity, which meets the technical requirements for rapid customs clearance of export food.
Comparative Analysis of Core Methods
| Technical Parameters | Traditional Culture Method | MALDI-TOF MS Method | Efficiency Improvement |
|---|---|---|---|
| Detection Cycle | 3-5 Days | 18-24 Hours | ↑70% |
| Sample Processing | Multi-step Biochemical Test | Single-step Protein Extraction | ↑85% |
| Result Judgment | Subjective Judgment | Automatic Database Matching | Accuracy↑30% |
Analysis of key operation points
1. Sample pretreatment
The standard requires the use of the formic acid-acetonitrile two-step extraction method: first, cells are lysed with 70% formic acid, and then impurities are precipitated with acetonitrile. In practical applications, please note:
- The colony culture time is strictly controlled within 18-24 hours (30±1℃)
- When spotting, it is necessary to form a uniform co-crystal with the CHCA matrix
2. Instrument calibration specifications
The BTS standard must be used for mass-to-charge ratio calibration to ensure that the error is less than 0.03%. Typical calibration parameters:
- Laser frequency: 60.0 Hz
- Accelerating voltage: 20 kV
- Detection range: 2000-20000 Da
Result judgment criteria
The matching scores were analyzed by Biotyper software, and the grading judgment criteria are as follows:
| Score range | Judgment conclusion | Handling suggestions |
|---|---|---|
| ≥2.300 | Reliable identification at the species level | Can be directly reported as positive |
| 2.000-2.299 | Reliable identification at the genus level | Supplementary biochemical tests are required |
| 1.700-1.999 | Suspicious results | Must be retested and confirmed |
Implementation suggestions and precautions
Key points of laboratory quality control
- Each batch of tests must include BTS standard as process control
- The matrix solution must be prepared and used immediately, and should be replaced immediately if precipitation occurs
- The mass spectrometry database should be updated to the latest version regularly
Biosafety requirements
All culture waste must be sterilized by 121℃ high pressure sterilization for 30 minutes, and the operator must have biosafety level 3 protection qualification.
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