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microbial diseases laboratory

Test Name 

Mycobacterial Culture and Acid Fast Bacilli (AFB) Smear from Primary Specimen

Test Methodology

Digestion and decontamination, inoculation onto liquid and solid culture media, acid-fast microscopy using fluorescent auramine-rhodamine stain, phenotypic and molecular (MALDI-TOF and Sequencing) on AFB-positive cultures.

Reflex Testing Criteria

If M. tuberculosis complex (MTBC) is isolated from a new patient, pyrosequencing and drug susceptibility testing will be performed, and isolate will be forwarded for TB Genotyping.

Pre-Approval Required

Yes. Consult with Mycobacterial & Parasitic Diseases Reference Unit before submitting specimens. Specimens sent without prior approval may not be tested.

Supplemental Information and Required Form(s)

Form LAB 402 (PDF) “Mycobacteriology-Specimens for Isolation and Culture”

Instructions on completing this form.

Required Specimen Type(s)

Performed on specimens from human sources. Respiratory specimens (sputum, bronchial alveolar lavage, etc.), tissue or body fluid. Swabs are suboptimal for culture and AFB Smear.

Minimum Volume Required

5 mL recommended; 1 mL minimum.

Specimen Stability

Room Temp: ≤ 1 hour. If transport is delayed more than 1 hour, refrigerate specimen.
Refrigerated (2 – 8°C): Maximum 7 days. Do not refrigerate CSF or blood.  Please note that specimens should ideally be submitted for processing as soon as possible after collection.
Frozen: not recommended

Rejection Criteria

  • Specimens with insufficient or conflicting labelling
  • Leaking specimens
  • Specimens with insufficient quantities
  • Specimens that are too old
  • Swab specimens and gastric fluid without neutralization
  • Other specimen/sample types not meeting acceptance criteria

Storage/Transport Conditions

Store and transport specimens at 2°C to 8°C; specimens should be submitted as soon as possible after collection.

Transport Medium, if applicable

Not applicable

Specimen Labeling

Two identifiers, including patient full name, and at least one other identifier (specimen accession number, date of birth, medical record number).

Collection date and time must be present on specimen containers for samples processed for AFB smear and mycobacterial culture.

Shipping Instructions and Specimen Handling Requirements

Ship as diagnostic specimen with cold or ice packs (do not freeze) using appropriate DOT/IATA approved shipping procedures. 

Ensure that culture isolates are sent in media flask or tubes containing a screw-top cap that is additionally sealed with parafilm or tape for additional protection against leaking.

Ship to:

California Department of Public Health
Microbial Diseases Laboratory
ATTN: Mycobacterial & Parasitic Diseases Ref. Unit
850 Marina Bay Parkway, Specimen Receiving Room B106
Richmond, CA 94804

Specimen Collection Instructions, if applicable

Guidelines (PDF) for collection of sputum specimens for tuberculosis testing are available from APHL website (see Appendix A).

Turnaround Time

8 weeks for negative cultures

3 weeks if culture is positive for Mycobacterium tuberculosis complex (MTBC)

4 weeks for mycobacteria other than MTBC (non-tuberculous mycobacteria, NTMs).

Preliminary reports will be issued if the MGIT becomes positive and AFB are observed.

Interferences & Limitations

The overgrowth of bacterial and/or fungal contaminants in positive cultures can prevent the isolation and identification of the acid-fast bacilli.

Reference Range

Not applicable

Additional Information


MDL Point of Contact

For questions regarding submissions, please email or call the MMPDS Section at 510-412-3924.
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