Mycobacteria Culture with Smear & Susceptibility Testing

Brief Description

The Mycobacteriology Unit accepts specimens from both public and clinical  healthcare providers for the isolation and identification of Mycobacterium tuberculosis (MTB) as well as nontuberculous mycobacteria (NTM) which can cause opportunistic infections in immunocompromised individuals. Three cultures per patient may be performed weekly if the cultures are smear/culture negative. After initial diagnosis, one culture will be performed weekly. Susceptibility testing is only performed on isolates of the Mycobacterium tuberculosis complex. 

Laboratory Unit

Mycobacteriology

Methodology

  • AFB Smear - Kinyoun / fluorochrome staining
  • AFB Culture - BD MGIT
  • AFB identification – Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF)
  • MTB susceptibility testing for primary drugs  – BD MGIT system

Specimen Collection

  • Expectorated Sputum:
    • An early morning, deep expectorated cough specimens collected on 3 consecutive days is best for initial diagnosis of tuberculosis. If sputa are collected within the same 24-hour period, a minimum of 8 hours between specimens is required. Preferred acceptable volume is 5-10 mL. Ship specimens each day collected to facilitate rapid diagnosis; do not hold until 3 specimens are collected
  • Induced Sputum:
    • If the patient has difficulty producing a sputum specimen, then induction should be considered. The inhalation of warm, aerosolized hypertonic (5-10%) saline irritates the lungs enough to induce both coughing and the production of a thin, watery specimen. This specimen collection should be performed in an area with appropriate air flow and with medically trained personnel using respirators.
  • Bronchial Washing:
    • Preferred acceptable volume is 5-10 mL
  • ​​​​​​​Gastric Lavage:
    • Should be performed early in the morning before eating and at least 8 hours after the patient has eaten or taken oral medication. Must be neutralized with 10% sodium carbonate soon after collection and transported to the laboratory within 24 hours after neutralization. Preferred acceptable volume is 5-10 mL
  • ​​​​​​​Body Fluids (CSF, pleural, synovial, etc.):
    • Must be aseptically collected and submitted in sterile containers
  • ​​​​​​​Urine:
    • A single, early morning voided midstream specimen or the total first morning specimen is acceptable. Preferred minimum acceptable volume is 40mL. Refrigerate until shipped.
  • Blood / Bone Marrow:
    • Submit in a blood collection tube containing heparin (green top) or sodium polyanethol sulfonate SPS (yellow top) Store tubes at room temperature until shipped
  • ​​​​​​​Tissue:
    • Must be aseptically collected in a sterile container without fixatives or preservatives.  May add sterile saline to keep the specimen moist. Do not place tissue specimen for culture into formalin
  • ​​​​​​​Swabs (Laryngeal/Wounds/Pus):
    • Swab must be aseptically collected and placed in a sterile container.  May add sterile saline to keep moist.
  • ​​​​​​​Fecal:
    • Place stool specimen in sterile collection container without preservatives or diluents.  Avoid contamination with urine.
  • Isolates for Identification and/or Susceptibility Testing:
    • Pure cultures submitted on solid media such as Middlebrook 7H10/7H11 or Lowenstein-Jensen slants. Cultures submitted in liquid 7H9 broth, MGIT, BacT/Alert MP bottles, VersaTREK bottles. Include preliminary identification and/or test results along with the GPHL Submission form. 

Storage/Transport

  • Ship specimens each day collected to facilitate rapid diagnosis; do not hold until 3 specimens are collected.
  • Expectorated Sputum can be maintained at refrigerated temperature (2-8°C) during transit.
  • Induced Sputum can be maintained at refrigerated temperature (2-8°C) during transit.
  • Bronchial Washing can be maintained at refrigerated temperature (2-8°C) during transit.
  • Gastric Lavage can be maintained at refrigerated temperature (2-8°C) during transit.
  • Body Fluids can be maintained at refrigerated temperature (2-8°C) during transit.
  • Urine can be maintained at refrigerated temperature (2-8°C) during transit.
  • Swabs can be maintained at refrigerated temperature (2-8°C) during transit.
  • Fecal can be maintained at refrigerated temperature (2-8°C) during transit.
  • Cultures can be maintained at refrigerated temperature (2-8°C) during transit.
  • Blood/ bone marrow can be maintained at room temperature (15-30°C) during transit. 
  • Download this pdf file. FRM-QA 4 Refrigeration Outfit Guide

Acceptable Specimen Type(s)

  • Sputum
  • Bronchial Washing
  • Gastric Lavage
  • Body Fluids
  • Urine
  • Blood/Bone Marrow
  • Tissue
  • Fecal
  • Swabs- (Laryngeal, wounds, pus)

Test Request

Possible Results

  • AFB Smear: 
    • 1+ (Rare)
    • 2+ (Few)
    • 3+ (Moderate)
    • 4+ (Many)
    • AFB Not Found
    • Smear Not Performed
    • Unsatisfactory
  • ​​​​​​​AFB Culture:
    • Mycobacteria Isolated
    • No mycobacteria isolated
    • Unsatisfactory
  • ​​​​​​​Susceptibility:
    • Susceptible
    • Resistant
    • Excessive growth
    • Insufficient growth
    • Culture contaminated
    • Unsatisfactory

Reference Range

N/A

Unacceptable Conditions

  • Missing testing requisition
  • Missing minimum of 2 patient identifiers
  • Improper labeling
  • Improper storage/transport of specimen
  • No specimen received (empty collection tube).
  • Wrong specimen type
  • Specimen damaged, broken, or leaking upon arrival

Interfering Substances

N/A

Result Reported

  • AFB smears: 1-3 business days
  • AFB cultures: Reported at 6 weeks if no growth occurs or when growth occurs and identification is made.
  • MTB susceptibility testing: Usually reported 10-14 days after identification of the organism

Fees

Download this pdf file. Fee schedule

LOINC/Order Codes

543-9 (Order code: 30000)