AFB Culture

Blood culture for AFB (includes smear) refer to C BAFB

C AFB

Culture for TB, Mycobacteria, MAC, MAI, Mycobacterium avium, or atypical Mycobacteria

Culture for AFB includes AFB smear (stain)

Pulmonary specimens such as:
Sputum, bronch wash, lung biopsy, pleural fluid

Extrapulmonary specimens such as:
Gastric aspirate, stool, urine, tissue, skin lesion, body fluid or bone marrow.

Note: Swabs of wound sites are not recommended and are only acceptable if a specimen cannot be collected by other means.

Body fluids: 5 mL (separate specimen should be submitted if mycobacterial cultures are required in addition to routine culture)
CSF: >5 mL (if chronic TB meningitis is suspected) 
Gastric lavage: 3 mL
Respiratory specimens: 5 mL (5-10 mL is preferred)
Urine: 40 mL x three separate specimens, over three consecutive days.
Stool: 1 gram solid stool or 5mL liquid stool
Tissue: 1 gram in small amount of sterile saline so as to not dry out.
Wound: Eswab or swab for AFB only (not shared with request for routine culture or fungal culture)

SPUTUM
1.  Submit no more than three consecutive specimens in 8 to 24 hour intervals, with at least one being an early morning specimen.
2.  For follow-up of patients (M. tuberculosis) on therapy, collect at monthly intervals beginning three weeks after initiation of therapy, until two consecutive specimens are negative on culture

GASTRIC ASPIRATE - Fasting and early morning samples are recommended (in order to obtain sputum swallowed during sleep)
1. Transfer gastric fluid from the syringe into a sterile container.
2. Add an equal volume of 8% sodium bicarbonate solution to the specimen to neutralize the acidic gastric contents and to prevent 
destruction of tubercle bacilli (contact the Micro Lab at BUMCP at 602-839-3481 for 8% sodium bicarbonate aliquots).
3. The final concentration of the sodium bicarbonate will be 4%.

STOOL
Stool for AFB: Collect fresh stool (1 gram solid or 5 mL or more liquid) in a clean, screw-capped container.
NOTE: Stool for AFB is ONLY recommended for patients with AIDS

URINE
1.  The patient should be on a minimal fluid intake from 9:00 p.m. the previous evening.
2.  The entire first morning urine (not midstream) should be collected in a sterile container, using more than one container if necessary.  A minimum of 40ml of urine is required.
3.  This procedure should be repeated for three separate specimens on three consecutive days to maximize conditions for recovery of M. tuberculosis.

BONE MARROW
1.  Preferred specimen ≥1 mL inoculated into a yellow vacutainer tube with SPS.
 [NOTE: 1 tube each per test ordered, i.e. one for Routine, one for AFB, one for Fungus Culture]

TISSUE or WOUND
1.  Preferred specimen ≥1g tissue in a sterile continer with a small amount of saline.
2.  A single swab must be provided for each test ordered, i.e. one for Routine, one for AFB, one for Fungus Culture
NOTE: Collection with swabs provides suboptimal amounts of material and may fail to yield acid-fast organisms. They are only acceptable if a specimen cannot be collected by other means.
 

For Sputum, Urine, Gastric aspirates or body fluids - sterile cup or sterile screw capped container or
Plain red (rubber) top vacutainer with NO additives, clot activators or serum separators
For Bone Marrow yellow vacutainer tube with SPS
For Stool: Collect fresh stool (1 gram solid or 5 mL or more liquid) in a clean, screw-capped container.
For Tissue: Collect in a clean sterile container
For Swab: Culturette or Eswab  

Refrigerated
CSF and Bone marrow may NOT be transported refrigerated. These specimens should be sent room/ ambient temperature.
Stool for AFB ONLY: May be frozen at -20°C if not processed the same day. One stool specimen is adequate.

Specimens are stable for up to 24 hrs at room temperature with the exception of Gastric aspirates. 

Gastric Aspirate
NOTE: Neutralization of gastric aspirate with 8% Sodium bicarbonate solution must occur within 4 hours of collection. Specimen is then stable for up to 24 hours at room temperature.

Unacceptable specimens:

• Swab specimen with concomitant request for AFB along with routine and/or fungal cultures.
• Any specimen with inadequate volume
• 24-hour pooled sputum, urine, or stool
• More than one sample from the same source within a 24-hour period
• Dry material
• Any specimen in formalin or other preservative
• Frozen Specimens (exception Stool)
• Specimens in expired transport media (unless irreplaceable)
• Leaking specimens (unless irreplaceable)
• Rectal swabs or stool on a swab
• Duodenal Aspirate
• Gastric aspirate NOT neutralized within 4 hours of collection
• Bone marrow specimens in anything other than an SPS tube. Reject Green top (heparin), Blue top (sodium citrate), Purple top (EDTA),Gray top (sodium fluoride)

AFB stain is reported <24 hours
A preliminary culture report will be available within 24 hours
A final negative report will be generated after 6 weeks
All positive cultures will be reported immediately 

There are more than 70 species of mycobacteria of which the primary pathogen is the M. tuberculosis complex. Tuberculosis is a chronic, granulomatous disease caused by the M. tuberculosis complex. Identification, and, if appropriate, antibiotic susceptibility testing, is required to initiate necessary therapy.