SIRE Supplement: Introduction, Composition and Function, Uses, and Keynotes

Introduction

The BACTEC™ MGIT™ 960 SIRE Supplement is an essential enrichment used specifically for drug susceptibility testing (DST) of Mycobacterium tuberculosis in the BD BACTEC™ MGIT™ automated system. 

The SIRE supplement is part of the MGIT™ 960 SIRE Kit. It is added to MGIT™ tubes along with specific first-line anti-TB drugs to determine if an isolate is susceptible or resistant to Streptomycin, Isoniazid, Rifampin, and Ethambutol. 

Composition and Function

While visually similar to the standard OADC Growth Supplement, the SIRE supplement is formulated specifically for DST. Its components per liter include: 

Component	Concentration (per Liter)	Primary Function
Bovine Albumin	50.0 g	Protects mycobacteria by binding toxic free fatty acids.
Dextrose	20.0 g	Acts as the primary energy source for bacterial growth.
Catalase	0.03 g	Neutralizes toxic peroxides that may inhibit growth.
Oleic Acid	0.6 g	Provides essential long-chain fatty acids for metabolism.

Uses

• Susceptibility Testing: Used to enrich the Middlebrook 7H9 broth to support growth during the testing of first-line drugs (STR, INH, RIF, EMB).
• Standardized Growth: Ensures that any inhibition of growth observed in the MGIT™ tube is due to the antibiotic’s effect rather than nutritional deficiencies.
• Result Interpretation: Facilitates rapid qualitative results, typically within 4–13 days.

Keynotes for Laboratory Practice

• Vial Volume: Standard SIRE supplement vials typically contain 20 ml of liquid.
• Dosing: In the standard SIRE procedure, 0.8 ml of supplement is added to each 7 ml MGIT tube before inoculation.
• Storage: Store at 2–8°C and protect from light. Once thawed, it should be used immediately and not refrozen.
• Caution: Do not use the PZA Supplement or standard MGIT™ Growth Supplement interchangeably with the SIRE supplement, as they have different formulations optimized for their specific tests.

Further Readings

1. https://ntep.in/index.php/node/4002/CP-critical-concentrations-and-reconstitution-sire-drugs
2. https://www.finddx.org/wp-content/uploads/2023/02/20061101_rep_mgit_manual_FV_EN.pdf
3. https://ntep.in/node/4001/CP-sire-susceptibility-testing
4. https://www.scribd.com/document/861249659/88-2041-1JAA-ZMG-D-RL-88-2041-1JAA
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC2772628
6. https://www.bd.com/en-in/products-and-solutions/products/product-page.245123
7. https://msa.sm.ee/ctrl/et/Fail/laadi_alla/160549
8. https://www.accessdata.fda.gov/cdrh_docs/pdf/K014123.pdf
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC88562
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC4172428
11. https://www.labx.com/item/becton-dickinson-bd-bactec-mgit-960-automated-mycobacterial/13277342