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🧪 AFB Rapid Culture – MGIT (Tissue/Biopsy)

Parameter	Details
Fasting Required?	❌ Not required
Sample Type	Tissue/Biopsy specimen (e.g. lymph node, lung, bone, intestinal wall)
Primary Purpose	Detect Mycobacterium tuberculosis complex (MTBC) or NTM
Main Organs Involved	Depends on biopsy site (lungs, lymph nodes, spine, intestines, etc.)

🔬 What is MGIT?

MGIT (Mycobacteria Growth Indicator Tube) is a liquid culture system that detects growth of mycobacteria in clinical samples.
It contains:
- Nutrient-rich broth
- Fluorescent oxygen sensor that glows as mycobacteria consume oxygen
It is more sensitive and faster than traditional solid cultures (e.g. LJ medium).

⏱️ Turnaround Time

Test	Time to Result
Smear Microscopy	1 day (low sensitivity)
MGIT Liquid Culture	7–14 days (positive cases), up to 42 days
Löwenstein-Jensen (LJ)	4–8 weeks

MGIT can also be used for drug susceptibility testing (DST) if positive.

🧠 When to Use MGIT Culture from Tissue?

Suspected extrapulmonary tuberculosis:
- Lymph node TB
- Spinal TB (Pott’s disease)
- Intestinal TB
- CNS TB (via brain biopsy)
Smear or GeneXpert-negative cases
Refractory or relapsing TB cases
Rule out NTM infections in immune-compromised patients

✅ Advantages of MGIT Culture

Benefit	Details
High Sensitivity	Can detect as low as 10–100 bacilli/mL
Faster Growth	Detects growth in 1–2 weeks vs 4–8 weeks for solid culture
Can detect NTM	Helps identify non-TB mycobacteria like M. avium, M. kansasii, etc.
Enables Drug Testing	Allows first-line and second-line drug resistance testing

🔗 Recommended Conjunction Tests

Test	Purpose
AFB Smear (ZN stain)	Quick detection but low sensitivity for tissue
GeneXpert (CBNAAT)	Rapid detection + rifampicin resistance in TB
Histopathology of Biopsy	Detects granulomas, caseation necrosis
TB-PCR (Tissue)	Molecular confirmation (especially if smear & culture negative)
ADA (if fluid present)	Supportive evidence in TB-rich sites

⚠️ Limitations & Considerations

Limitation	Detail
Needs Biosafety Lab	Requires BSL-3 level infrastructure due to live TB culture
May take time	Though faster than solid culture, can still take 2–6 weeks
Contamination Risk	Liquid medium is more prone to contamination

✅ Summary Table

Test Name	AFB Rapid Culture – MGIT (Tissue/Biopsy)
Purpose	Definitive diagnosis of extrapulmonary TB
Detects	MTB and NTM
Time to Result	7–14 days (positive); up to 42 days
Paired With	GeneXpert, AFB smear, histopathology
Sample Required	Sterile biopsy/tissue specimen (fresh preferred)

AFB Rapid culture by MGIT - Tissue/Biopsy