David A, Scott LE, Da Silva P, Mayne E, Stevens WS. Storage of
Mycobacterium tuberculosis culture isolates in Microbank
TM beads at a South African laboratory.
Afr J Lab Med 2023;
12:2172. [PMID:
38023785 PMCID:
PMC10646387 DOI:
10.4102/ajlm.v12i1.2172]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Accepted: 08/23/2023] [Indexed: 12/01/2023] Open
Abstract
Background
Mycobacterium tuberculosis complex (MTBC) isolates are typically stored at -70 °C in cryovials containing 1 mL aliquots of a liquid medium, with or without 50% glycerol. Multiple uses of the culture stock may decrease the strain viability while increasing the risk of culture contamination. Small culture aliquots may be more practical; however, storage capacity remains challenging. MicrobankTM beads (25 beads/vial) for the long-term storage of fungal cultures is well documented, but their use for storing MTBC isolates is uninvestigated.
Objective
The study aimed to determine the feasibility of using MicrobankTM beads for long-term storage of MTBC isolates at a laboratory in South Africa.
Methods
In February 2020, 20 isolates in liquid culture were stored in MicrobankTM beads, following an in-house developed protocol, at -70 °C. At defined time points (16 months [15 June 2021] and 21 months [18 November 2021]), two beads were retrieved from each storage vial and assessed for viability and level of contamination.
Results
Stored liquid isolates demonstrated MTBC growth within an average time-to-detection of 18 days following retrieval, even at 21 months post storage. Contaminating organisms were detected in 2 of 80 (2.5%) culture isolates.
Conclusion
MicrobankTM beads will allow for the reculture of up to 25 culture isolates using a reduced culture volume compared to current storage methods. MicrobankTM beads represent a storage solution for the medium-term storage of MTBC isolates.
What this study adds
This study evaluated the use of MicrobankTM beads as an alternate method for storing MTBC culture isolates at -70 °C and provided a suitable option for medium-term storage of MTBC.
Collapse