Storage of Culture Isolates

Maintenance and Storage of Mycobacterial Strains

Strains may be well-characterized clinical isolates or culture collection strains (e.g. American Type Culture Collection, ATCC). Mycobacterial strains must be stored in adequate conditions to preserve their viability and intact genetic background. Maintenance of mycobacterial cultures by re-inoculating media during prolonged time may cause accumulation of mutations that can lead to unpredictable results. 

Steps to preserve and store MTB cultures 

1. From culture on solid media

1. Prepare suspension equal to McFarland 1.0 standard from a culture not older than two weeks after growth appearance.

2. Label sterile screw-capped cryovials with laboratory number, study reference and date of preparation

3. If suspensions are from quality control strains, label them with name, ATCC number, batch number and date of preparation.

4. Distribute the suspension into sterile screw-capped cryovials.

5. Put the cryovials into a numbered storage box. 

6. Put the storage box into the -80C freezer.

7. Record the location and strain identifiers in the -80°C Freezer Storage Logbook.

    

   2. From liquid culture

8. Label sterile screw-capped cryovials with laboratory number, study reference and date of preparation

9. If cultures are from quality control strains, label them with name, ATCC number, batch number and date of preparation.

10. Distribute the suspension into sterile screw-capped cryovials.

11. Put the cryovials into a numbered storage box. 

12. Put the storage box into the -80°C freezer.

13. Record the location and strain identifiers in the -80°C Freezer Storage Logbook.

     

    Storage

     

    Short-term storage

• Cultures on solid media can be stored at room temperature in the dark for several months and 4°C  for two years.

• Liquid cultures can be maintained viable at 4°C  for several months. 

   

   Long-term storage

• Cultures can be stored at -20°C  for several years and at -80°C  for decades.

   

   

  Resource

   

Mycobacteriology Laboratory Manual 

Assessment

• Question​	Answer 1​	Answer 2​	Answer 3​	Correct answer​	Correct explanation​	Page id​	Part of Pre-test​	Part of Post-te
  Cultures can be stored for how long?	-20°C  for several years	-80°C  for decades.	Both 1 &2	Answer 3: Both 1 &2	Cultures can be stored at -20°C  for several years and at -80°C  for decades.		Yes	Yes