Procedure of Quality Control for DST

Quality controls procedures are essential to generate quality DST results. Quality procedures are essential when using QC strains and reagents and preparing and using drugs for DST. These include:

QC strains
​1. Use well-characterized pan-susceptible M. TB strain/ H37Rv/ M. tuberculosis ATCC 27294 
2. Colonies from solid media less than 14 days old​
3. MGIT 960 tube 1–5 days after flagged positively by instrument ​
4. Additional organisms may be tested to supplement BD QC recommendations ​
5. Test with a known pan-susceptible strain of M. tuberculosis

Drug and Inoculum Preparation​
1. Ensure proper reconstitution of lyophilized drugs​ by following the given guidelines:

• Rehydrate drugs with sterile distilled water​
• Thaw aliquots of prepared drugs from freezer​
• Check the expiry date before use​

2. Avoid wrong drug concentrations. ​
3. Avoid improper drug preparation.​
4. Proper dilution of inoculum for drug and growth control tube is critical.
5. Suspension must be well mixed and homogeneous without clumps.
6. Prepare QC inoculum (H37Rv) suspension in the same way as patient isolate suspension.

7. Use positive and negative controls.

8. Follow standard operating procedures to perform SIRE/ Second-line and PZA DSTs​.

Resource

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