Liquid culture Practical challenges with MGIT

Transcription

1 Reality check! Ensuring the pertinence of TB diagnostic tools for the peripheral l level Médecins Sans Frontières res Satellite IUATLD Conference,, Palais des Congrès, PARIS Sunday 19th October 2008 Liquid culture Practical challenges with MGIT Anandi Martin, PhD Institute of Tropical Medicine, Antwerp, Belgium

2 Liquid culture media June 2007: WHO recommends the use of liquid medium for culture and DST in middle- and low-income countries /tb/dots/laboratory/policy/en/index3.htlm MGIT 960

3 MGIT principle It is based on fluorescence detection of mycobacterial growth. Fluorescence can be read with an UV lamp or a small reader (manual MGIT) or automated (MGIT960). Reading system for manual MGIT Automated reading for MGIT 960

4 Liquid medium (MGIT) What do we need? 1.Appropriate biosafety level (BSL) 2.Commitment of the manufacturer 3.Appropriate training of staff 4.Maintenance of infrastructure and equipment

5 MGIT advantages Reduce the delay in obtaining results MGIT reduces the time to results: days rather than weeks. For DST delay may be reduced to 10 days compared to days with conventional solid media. Increase the sensitivity MGIT is more sensitive for the detection of mycobacteria and may increase the case detection by 10% over solid media. Capacity to incubate up to 960 tubes at the same time.

6 MGIT 960 Due to its high sensitivity and the reduced delay in time to results the MGIT system contributes significantly to improve patient management

7 MGIT: disadvantages Liquid culture is more complex to perform Because... Increases contamination. Increases isolation of non-tuberculous mycobacteria. Cross-contamination can happen: transfer of bacilli from positive to negative samples especially when a lot of positive samples are processed. Needs rapid method to identify M. tb complex in all positive cultures before diagnosis can be confirmed. More expensive than solid media.

8 What does it mean automated system? The use of automated MGIT system does not mean that all manipulation is automated! Only reading of the tubes is automated!

9 Anandi Martin, Armenia Yerevan

10 Anandi Martin, Armenia Yerevan

11 What does it mean automated system? The use of MGIT requires daily removal of positive/negative tubes from the machine

12 What does it mean automated system? To perform ZN Detection of contamination (blood( agar plate 48h). Identification test => Confirmation M. tuberculosis complex Identification test: capilla?, LJ+PNB? molecular test?

13 Identification test? Species identification: a MGIT positive tube/afb positive does not tell you that it is M. tuberculosis! Need an identification method to differentiate between M. tuberculosis and NTM? Which method? Capilia test is not yet commercially available. Which test is recommended for identification? No guidelines. If MGIT is a rapid method, the identification test should be rapid but today in practice what should we do? Classical method (LJ+PNB 2 weeks extra to have results) Molecular test (1 day, expensive, need kits, need equipment)

14 Limitations MGIT has 3 drawers (A), (B), (C): 320 tubes/drawer drawer. Cannot choose to print the status of one sample.. You have to print the results of all 320 samples together. Needs a lot of ink and paper! To avoid printing so much paper: Epicenter Software is available (around Euros in addition to the cost of the machine euros!)!)

15 Infrastructure Liquid culture produces aerosol during manipulation and can be dangerous for staff! Laboratory diagnosis of TB involves a risk of infection for laboratory personnel. TB biosafety measures are often neglected.

16 Infrastructure All manipulations should be done in a biological safety cabinet (BSC) and DST must be performed in Level 3 laboratory. Most limited-resource countries have major constraints for successful implementation of level L2/L3 lab (staff( staff, maintenance etc.)

17 Equipment Laboratory should be equipped with air- conditioning system. High temperature can affect the stability of reagents and all electronic control machanism of lab equipment.

18 Electrical Supply and Power Back-up The MGIT 960 requires constant electricity Back-up electrical power is necessary to maintain constant incubator temperature and prevent data loss In laboratories where power is often lost the machine should be connected to back up generator picture: courtesy Prof. Knut Feldmann

19 Training Training is needed for use of the MGIT culture and DST to work properly with the system. Access to external technical assistance from BD is important and needed. Technical Support and Maintenance is essential.

20 Problems that could occur (1) Procurement of MGIT tubes Delays due to delivery, shipment, customs clearance have to be considered. MGIT tubes, reagents ( SIRE( SIRE kit, OADC, supplement) should be ordered a long time in advance (around 3 months) to avoid a rupture of stock.

21 Problems that could occur (2) MGIT tubes or drug kits are not always available in stock at the manufacturer. Some reagents have short shelf-lives lives (about half a year or less) and may have even shorter expiry dates upon arrival. Therefore inventory management and ordering system needs attention.

22 Conclusion: implementation issue MGIT for rapid culture and DST would be possible if : 1. Have funding (machine, software, tubes, reagents). 2. Safe lab with a very good high laboratory level. 3. Well trained staff. 4. Special media to detect contaminations. 5. Maintenance, support of BD close to your country. 6. Stable electricity. 7. Basic things (distilled water). Implementation of the MGIT system is a big challlenge!

23 Thanks for your attention!