MGIT Can Be Performed on Tissue Samples
Yes, MGIT (Mycobacteria Growth Indicator Tube) can be performed on tissue samples, but the tissue must be ground aseptically in sterile physiological saline or bovine albumin before direct inoculation onto the media. 1
Tissue Processing Requirements
The ATS/IDSA guidelines specifically address tissue specimen processing for mycobacterial culture:
- Tissue specimens should be ground aseptically in sterile physiological saline or bovine albumin before being directly inoculated onto culture media 1
- The grinding process is essential to release mycobacteria from the tissue matrix and create a homogeneous suspension suitable for culture 1
Culture Method for Tissue Specimens
Once properly processed, tissue specimens follow standard mycobacterial culture protocols:
- Both solid and liquid media should be used for optimal detection, as liquid media (MGIT) provides higher yield and faster results while solid media serves as backup and allows colony morphology assessment 1
- The MGIT system uses modified Middlebrook 7H9 broth with a fluorescence-based oxygen sensor to detect mycobacterial growth 1
- Incubation should continue for a minimum of 6 weeks, as the vast majority of pathogenic mycobacteria will grow within this timeframe 1
Clinical Context from Research
Research confirms MGIT's utility with tissue specimens:
- A study examining FISH methods for mycobacterial identification included 4 tissue samples among 60 MGIT-positive specimens, demonstrating successful culture from tissue sources 2
- The MGIT 960 system achieved detection times averaging 13.3 days, significantly faster than solid media (25.6 days), making it particularly valuable for tissue specimens where rapid diagnosis impacts clinical management 3
Important Caveats
Tissue specimens do not require the decontamination steps used for respiratory samples (NALC-NaOH treatment), as they are typically sterile specimens 1. This is a critical distinction—applying standard respiratory specimen decontamination protocols to tissue would unnecessarily reduce mycobacterial viability.
The combination of proper tissue grinding followed by inoculation into both MGIT liquid media and solid media provides the highest diagnostic yield for detecting mycobacteria from tissue specimens 1.