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  • MGIT 960 DST Equipment and Reagents Troubleshooting

    Content

    MGIT 960 DST Equipment and Reagents Troubleshooting

    If the BACTEC™ MGIT™ instrument malfunctions or operates unusually in any way, an error message will appear on the instrument. These messages are in numerical order, along with possible causes of the message and corrective actions are listed below.

    Table: Errors encountered during the operation of the BACTEC™ MGIT™ instrument and their corrective actions

    Error Code

    Description

    Troubleshooting/Corrective Action

    E01

    The software algorithms that determine tube positivity have been reset. This message is informational.

    E01 is an informational message, and requires no corrective action per se.

    E02

    Temperature alarm; An incubator or drawer temperature is too high or too low.

    Check current incubation temperature, room temperature, and thermometer tube. Keep drawers closed. Clean/replace air filters. Remove the instrument from direct sunlight or any other heat source.

    E04

    Flash cache error; System encountered a software error.

    Save data to the disk and call BD.

    E05

    Calibration error; A calibrator reading is out of tolerance.spilt

    Check for and clean any debris/spilt media in Instrument. If an error recurs, replace the calibrator.

    E06

    Detector error; Detector assembly motion was impeded.

    Check for and remove any object impending motion of detector assembly. Reboot instrument and call BD.

    E07

    Power supplies high/low; Problem detected in the instrument power supply.

    Contact local BD representative for assistance. Do not reboot the instrument.

    E08

    Drawer Voltage high/low

    Check line voltage. Clean/replace air filters. Reboot instrument. If the error recurs, note any error sub-codes.

    E09

    No test in over 4 hours; Instrument has been off for longer than 4 hours.

    Determine why the test has not occurred (e.g., power off, drawer openings interrupted testing etc). If none of these events happens, save data to disk and call BD. 

    E10

    Database corruption. Database checksum test failed.

    Save data to disk and call BD.

    E11

    Printer error; Printer paper is jammed or exhausted.

    Check paper and clear jam or add paper if necessary.

    E12

    Station error

    Check that tubes are seated in stations. Determine why the tube is missing from the station.

    E13

    Power failure; Power was removed from the instrument.

    Note power failure and restore time in the instrument log (or print screen).

    E30

    An unexpected tube was scanned.

    Locate the missing tube or press the “force station available” soft key.

    E31

    Diskette error; The floppy disk is not inserted, not formatted,  is write-protected, or is full. 

    Insert formatted floppy disk/ Move write-protect tab toward center of floppy disk/Use a new floppy disk.

    E32

    The drawer is full, No available stations.

    Try entering the tube in another drawer (with available stations). If there are no available stations in other drawers, remove the final negative tubes if any exist.

    E33

    Moved the tube with no error

    Refer to the BACTEC™ MGIT instrument user manual.

    E34

    Update error

    Redo software update

    E35

    Incorrect drawer. Tube just scanned belongs in another drawer.

    Open the next drawer and scan the tube barcode until the error does not recur.

    E37

    The Barcode scan order is incorrect. The system expected a barcode sequence number, and the accession barcode was scanned (or wise versa).

    Be sure to scan the type of barcode that the system expects.

    E38

    No floppy disk in the drive 

    Insert a blank, formatted, write-enabled floppy disk in the disk drive to complete the save data to disk.

    E39

    Floppy disk full

    Insert a blank, formatted, write-enabled floppy disk in the disk drive to complete the save disk function. 

    E45

    Drawer error. A drawer is not fully closed.

    Close the drawer properly.

    E50

    Internal software error. System encountered a software error

    Save data to disk and call BD.

    E92

    AST set error

    Main error code for any station error in AST set. Refer to the BACTEC™ MGIT instrument user manual for additional information.

     

     

    Resource

    Mycobacteriology Laboratory Manual

    Assessment

     

    Question​

    Answer 1​

    Answer 2​

    		 Answer 3 Answer 4

    Correct answer​

    Correct explanation​

    Page id​

    Part of Pre-test​

    Part of Post-test​

    E12 Which of the following is a temperature alarm? alarm?

    		 E01 E02 E30 E31

    2

    E02 is a temperature alarm. An incubator or drawer temperature is too high or too low.

    YES

    YES

     

  • MGIT 960 DST Inoculum Troubleshooting

    Content

    MGIT 960 DST Inoculum Troubleshooting

    MGIT DST results should be available within 4-13 days (SIRE and other second-line drugs) or 4-21 days (PZA) if the standard procedure is followed. However, under certain conditions, the results of the DST are reported as errors. These errors are mostly due to improper inoculum used for the DST. These errors, along with possible causes and corrective actions,  are listed below:

    Error Code

    Description 

    Possible Causes

    Corrective action/s

    X200

    GU of the growth control tube was less than 400 at the end of the specified protocol time. 

    Often a result of too little inoculum

    •    Ensure that the DST was not set up on the same day the  primary MGIT tube signalled positive.

    •   Ensure that the primary culture was diluted appropriately before inoculating ( 1:5 dilution if the DST was set up between three and five days after signalling positive and undiluted If the culture was worked up one or two days after signalling positive)

    X400

    GU of the growth control tube reached 400 before the specified protocol time. 

    Often a result of an over-inoculated tube

    •   Ensure that the primary culture was pure.

    •     Ensure that the primary MGIT culture was not older than 5 days after signalling positive.

    •     Ensure that a 1:5 dilution was made if the DST was set up between three and five days after signalling positive

    •     Ensure that the Saline used for inoculum dilution was sterile. 

     

     

    Resources: 

    Mycobacteriology Laboratory Manual. 

     

    Assessment

    Question​

    Answer 1​

    Answer 2

    Answer 3

    Answer 4

    Correct answer​

    Correct explanation​

    Page id​

    Part of Pre-test​

    Part of Post-test​

    What is the reason for the X200 error in DST?

    Over inoculum 

    Under inoculum  

    No inoculation 

    Contamination 

    2

    X200 error is often a result of too little inoculum.

     

    YES

    YES
    What is the reason for the X400 error in DST?

    Over inoculum 

    Under inoculum  

    No inoculation 

    Contamination 

    1

    		 X400 is often a result of an over-inoculated tube.  

    YES

    YES

     

  • Troublsehooting Invalid DST Sets " X"

    Content

    Error or indeterminate DST results are reported when certain conditions occur that may affect the test. These results are designated by the alphabet ‘X’ followed by a code. Following two types of such errors are encountered:

    1.        X200 = Occurs when the system cannot detect a sufficient indication of growth in the Growth Control tube in the specified protocol time (i.e., 13 days for  SIRE or 21 days for PZA) and does not provide an interpretation of the AST set results. Often a result of too little inoculum, nonviable organisms, or a slow-growing drug-resistant strain. 

        Troubleshooting: In this case, repeat testing with a pure culture of the isolate is recommended.

    2.  X400 = Occurs when the system detects indications of sufficient growth in the growth control (GC) tubes in less than four days. It may be a result of a possible contamination or over-inoculated tube. 

        Troubleshooting: Check the GC tube for turbidity, prepare a ZN smear and subculture to a blood agar (BA) or brain heart infusion (BHI) agar plate     and interpret as below:

     

    Condition

    Interpretation

    Control is visually turbid. 

    ZN – positive

    BAP/BHI– growth

    Culture positive for AFB and contaminated.

    Verify original culture was MTB, purify if MTB, and repeat the test.

    Control has no visual contamination.

    ZN – positive 

    BAP/BHI – no growth

    Over-inoculation; Repeat the test

    Control is either visually turbid or clear

    ZN – negative

    BAP/BHI – growth

    Culture contaminated.

    Verify original culture was MTB and repeat test.

    Resources

    1. Mycobacteriology Laboratory Manual

    2. Revised National TB Control Programme Training Manual for Mycobacterium tuberculosis Culture & Drug susceptibility testing, Central TB Division, Ministry of Health and Family Welfare, GOI

    Assessment

    Question​

    Answer 1​

    Answer 2​

    		 Answer 3 Answer 4

    Correct answer​

    Correct explanation​

    Page id​

    Part of Pre-test​

    Part of Post-test​

    X400 occurs if the system detects growth in the GC before four days.

    True

    False

    		    

    1

    X400 = Occurs when the system detects indications of sufficient growth in the growth control (GC) tubes in less than four days.  

     

    YES

    YES
    How can you troubleshoot X200? Re-inoculation of the growth tube Repeat testing with a pure culture Subculture on Blood Agar Prepare a ZN smear 2

    X 200 occurs due to insufficient growth within the specified protocol time (i.e., 13 days for  SIRE or 21 days for PZA) due to too little inoculum, nonviable organisms, or a slow-growing drug-resistant strain. In this case, repeat testing with a pure culture of the isolate is recommended.

    		   YES YES

     

  • Troubleshooting Non-interpretable DST Results

    Content

    Troubleshooting Non-interpretable DST

     

    MGIT DST results should be available within 4-13 days (SIRE and other second-line drugs) or 4-21 days (PZA) if the standard procedure is followed. However, under certain conditions, the Instrument takes too long to read the tubes, and the results are reported uninterpreted. The reasons for these non-interpretable results, along with the suggested corrective action, are listed below:

     

    Reason 

    Suggested corrective action

    Initial inoculum too light

    • Precise pipettes must be used for dilutions and addition to tubes.

    • If working with solid media, ensure that the media is not picked up during inoculum preparation. This interferes with reading 0.5 McFarland.

    Initial culture too old

    Ensure that the cultures selected for DST are in proper growth phase.
    Initial inoculum too heavy Day 3-5 growth from MGIT tube to be diluted; if working from solid media, allow tube to settle and adjust suspension; Avoid clumps in suspension.
    GC suspension for SIRE and PZA are different (1:00 vs 1:10) Prepare suspension carefully.

     

     

    Resources: 

    Mycobacteriology Laboratory Manual. 

     

    Assessment

     

    Question​

     

     

    Answer 1​

     

     

    Answer 2

     

     

    Answer 3

     

     

    Answer 4

     

     

    Correct answer​

     

     

    Correct explanation​

     

     

    Page id​

     

     

    Part of Pre-test​

     

     

    Part of Post-test​

     

     
    MGIT DST for first and second-line drugs should be available in how many days? 3 days 7 days  4-13 days 21 days  3 MGIT DST results should be available within 4-13 days (SIRE and other second-line drugs) or 4-21 days (PZA) if the standard procedure is followed.

     

    YES

     

     

    YES

     

     
                       


     

  • Troubleshooting False Susceptible DST Results

    Content

    Troubleshooting False Susceptible DST Results

     

    The common reasons for getting false susceptible DST results, along with their corrective actions, are given in the table below:

     

    Reason

    Corrective action

    Inoculum too light

    • Ensure that precise pipettes are used for dilutions and addition to tubes.

    • Ensure that the starting suspension is > 1.0 McFarland (in case of solid media).

    Suspension not homogeneous

    Ensure that the starting suspension is uniformly homogenized.

    Culture too old

    Ensure that the cultures selected for DST are in the proper growth phase.

    Growth control grew too fast

    Ensure that proper dilutions are used for inoculating the growth control tube.

    Proper amount of supplement the not added to the tubes

    Ensure that correct amount of supplement (as per the standard protocol) is added to the tubes.

    Supplement not stored properly 

    Ensure that the supplement is stored as per the manufacturer’s instructions.

    Drugs  not reconstituted properly

    Ensure that the lyophilized drugs are reconstituted as per the manufacturer’s instructions.the 

    Too much drug added to tubes

    Ensure that exact volume (100 µl) of the drug is added to the tube.

    Incorrect media and/or supplement used for PZA

    Ensure that PZA medium and PZA supplement is used for PZA DST.

    Organism could be borderline-resistant

    Check the Growth units and repeat DST if GU is >95 but <100. 

      

     

    Resources

    GLI Practical Guide to TB Laboratory Strengthening

     

     

    Assessment

    Question​

    Answer 1​

    Answer 2

    Answer 3

    Answer 4

    Correct answer​

    Correct explanation​

    Page id​

    Part of Pre-test​

    Part of Post-test​

    In the case of solid media, the initial suspension to be used for DST must satisfy which of the following conditions?

    > 1.0 McFarland

    > 2.0 McFarland

    <1.0 McFarland

    None of the above

    1

    Ensure that the starting suspension is > 1.0 McFarland (in case of solid media).

     

    YES

    YES

  • Troubleshooting False Resistant DST Results

    Content

    Troubleshooting False Resistant DST Results

    The common reasons for getting false resistant DST results, along with their corrective actions, are given in the table below:

     

    Reason

    Corrective action

    Culture .contaminated or mixed culture

    Ensure the purity of the culture before DST

    Organism inoculum too heavy

    • Ensure that precise pipettes are used for dilutions and addition to tubes.

    • Ensure that the starting suspension is > 1.0 McFarland (in case of solid media).

    Suspension not homogeneous or had clumps

    Ensure that the starting suspension is uniformly homogenized.

    Growth control dilution  too light

    Ensure that proper dilutions are used for inoculating the growth control tube.

    Drug not reconstituted properly

    Ensure that the lyophilized drugs are reconstituted as per the manufacturer’s instructions.

    Drug not stored properly

    Ensure that the reconstituted drugs are stored as per the manufacturer’s recommendations.

    Drug not added to the tube

    Ensure that the exact volume ( 100 µl) of the drug is added to the tube.

    MGIT tube not mixed properly after the addition of the organism suspension

    Ensure that MGIT tubes are mixed properly before loading the AST carrier into the MGIT instrument.

    Organism could be borderline-resistant

    Check the Growth units and repeat DST if GU is >95 but <100. 

     

    Resources

    GLI Practical Guide to TB Laboratory Strengthening

     

     

    Assessment

    Question​

    Answer 1​

    Answer 2

    Answer 3

    Answer 4

    Correct answer​

    Correct explanation​

    Page id​

    Part of Pre-test​

    Part of Post-test​

    During DST, what is the volume of drug which must be added to the MGIT tubes?

    100 µl

    1000 µl

    2.5 ml

    4.0 ml

    1

    Ensure that the exact volume ( 100 µl) of the drug is added to the tube.

     

    YES

    YES

     

  • Troubleshooting Unexpected/False Profile of DST Isolates

    Content

    The cause for the unexpected/false profile of DST isolate can be due to various reasons that reflect quality aspects of the laboratory as well as the characteristic of the MGIT growth. The following need to be looked into as cause for unexpected/false profiles of DST isolate:

    1. Laboratory procedures:

    • Organism inoculum too light ​
    • Inoculum not pure
    • Suspension not homogeneous
    • Culture too old ​
    • Growth control dilution too heavy ​
    • Supplement not properly added to tubes and stored
    • Drugs not reconstituted properly ​
    • Too much drug added to tubes
    • Pipetting errors
    • Tubes not capped tight during incubation such that oxygen can leak into the tube ​

     

    2. Characteristics of MGIT growth
     

    • Organism could be borderline-resistant ​
    • MTBC mixed with NTM

    Quality laboratory procedures for standard operating procedures, reagents and calibrated instruments should be followed to prevent unexpected/false DST profiles. Regarding unexpected results due to growth characteristics, perform definitive identification​ for the growth, perform ZN smear on positive MGIT tubes, identify MTBC, and identify NTMs that show resistance to anti-mycobacterial drugs. 

    Resource

    GLI Practical Guide to TB Laboratory Strengthening

     

    Assessment

    Question​

     

     

    Answer 1​

     

     

    Answer 2

     

     

    Answer 3

     

     

    Answer 4

     

     

    Correct answer​

     

     

    Correct explanation​

     

     

    Page id​

     

     

    Part of Pre-test​

     

     

    Part of Post-test​

     

     

    False/unexpected DST is due to which of the following reasons?

     

     

    High inoculum

     

     

    Mixed culture

     

     

    Improper drug addition

     

     

    All of the above

     

     

    4

     

     

    False/unexpected DST is caused by high inoculum, mixed culture, and improper drug addition.

     

     

     

    YES

     

     

    YES

     

     

     

    ​

     

     

  • Retesting MGIT DST Results

    Content

    Retesting MGIT DST Results

    Following are the instances when we need to re-test the MGIT DST results:

    • The final DST results are non-interpretable.
    • Unusual DST results, e.g., Mono-resistance, are obtained.
    • DST results disagree with the previous testing from the same patient.
    • Borderline resistance/susceptibility is identified.
    • The patient is a new untreated case and shows resistance (primary drug resistance).
    • Quality Control organisms fail to give expected results.
    • An unexpectedly high number of resistant isolates in a batch.

     

    Resource

    GLI Practical Guide to TB Laboratory Strengthening

     

     

    Assessment

    Question​

    Answer 1​

    Answer 2

    Answer 3

    Answer 4

    Correct answer​

    Correct explanation​

    Page id​

    Part of Pre-test​

    Part of Post-test​

    Retesting of MGIT DST is done for which of the following reasons?

    The final DST results are non-interpretable.

    Borderline resistance/susceptibility is identified.

    Quality Control organisms fail to give expected results.

    All the above

    4

    Retesting of MGIT DST is done if the final DST results are non-interpretable, if the organism is borderline resistant/susceptible or when QC organisms fail to give expected results.

     

    YES

    YES