Mycobacteria – Culture, Sensitivity and PCR (Bacteriology)
Collection container (including preservatives):
Use aseptic technique
Collect specimens in appropriate CE marked leak proof containers
and transport in sealed plastic bags.
Specimen type: Sputum, gastric washing, sterile
site body fluids (CSF, pleural fluids etc), urine, skin or tissue
biopsies, bone marrow, bronchoalveolar washings, blood, post-mortem
Collection: If sample volume is insufficient
for both, culture is usually preferred to microscopy due to greater
Specimen transport: Specimens should be
transported and processed as soon as possible. Specimens should be
transported and received in the laboratory within one working day
of collection and processed as soon as possible.
Requirements of individual testing laboratories should be
If processing is delayed, refrigeration is preferable to storage
at ambient temperature.
- Blood and Bone Marrow - Request the MB/BacT blood culture
bottles from the laboratory on 291 4424, and request a porter to
collect. These bottles MUST NOT be sent via the pod system.
- Sputum specimens - Sputum specimens should be relatively fresh
(less than 1 day old) to minimise contamination. Purulent specimens
are best. Three samples of ≥5mL should be collected approximately
8-24 hours apart with at least one from early morning.Samples taken
early morning (ie shortly after patient waking) have the greatest
yield. When the cough is dry, physiotherapy, postural drainage or
inhalation of nebulised saline ('sputum induction') before
expectoration may be helpful.
- Bronchoalveolar lavage/bronchial washings - These may be sent
if spontaneous or induced sputum is unavailable or if such
specimens are AFB smear negative. Note: Contamination of the
bronchoscope with tap water, which may contain environmental
Mycobacterium species, should be avoided. Minimum sample
size is preferably 5mL.
- Urine specimens - Whole urine specimens should be collected in
the early morning on three consecutive days in a CE marked leak
proof container (that does not contain boric acid), and placed in a
sealed plastic bag.
- Sterile site body fluids - Sterile site body fluids (CSF,
pleural fluid, etc) will normally not require decontamination, and
can be inoculated directly to neutral media. However, sterile site
body fluids can be treated with acid if necessary. Collect
aseptically as much (eg >6mL in adults) CSF sample as possible
into a CE Marked leak proof container in a sealed plastic bag. If
only a small volume is available after initial lumbar puncture, and
the findings of cell counts and protein suggest TB meningitis, a
second procedure should be considered to obtain a larger volume to
improve chances of achieving positive cultures. It should be noted
that pleural or pericardial fluids are not very sensitive samples
for the detection of M. tuberculosis, and that a
concurrent pleural or pericardial biopsy taken with the fluid is
more useful. A negative result on these fluids does not rule out
Minimum volume of sample:
- 1mL of Sputum
- 5mL of BAL
- 6mL of CSF
Special precautions: For the initial diagnosis
of mycobacterial infection all specimens should be fresh and taken,
whenever possible, before anti-tubercular treatment is started.
'Other' antimicrobials may also have significant anti-mycobacterial
activity, notably the fluoroquinolones such as ciprofloxacin,
levofloxacin or moxifloxacin, and the macrolides such as
clarithromycin or azithromycin.
Measurement units: Not applicable
Biological reference units: Not applicable
Urgent microscopy available within 2 hours
Culture 3 weeks (incubation continued for 6 weeks)
Mycobacterium PCR available within 3 days
Clinical decision points: Not applicable
Factors known to significantly affect the
results: EDTA, even in trace amounts, inhibits the growth
of some Mycobacterium species.