For expectorated sputum, the patient must
be fully cooperative and must understand that oral secretions are not helpful.
The patient should be instructed to bring up a deep specimen and cough it
into a sterile specimen cup.
Expectorated sputum will first be evaluated
for quality by gram stain. Specimens that show significant contamination
with upper respiratory secretions (i.e., large numbers of squamous epithelial
cells) will not be processed for bacterial culture except for Legionella,
as accurate identification of significant lower respiratory pathogens will
not be possible. The report will indicate that the specimen is contaminated
and that another specimen should be sent if clinically appropriate.
Note: expectorated sputums are NOT suitable for Pneumocystis carinii detection.
Sputum induction with nebulized hypotonic
saline may be necessary if the patient cannot provide an adequate expectorated
sputum. This is performed per protocol by the Respriatory Therapists. Place
sputum into a sterile specimen cup. Note that a special protocol must be
followed for induction for Pneumocystis carinii detection.
For the intubated patient, tracheal aspiration or endotracheal lavage are 2 methods for
obtaining sputum. The traps used for these methods tend to leak easily. Check
to ensure a tight fit on the trap, or transfer the contents to a cup that
can be closed well.
Fungal cultures on sputum are rarely required
because the most frequent pathogen, Aspergillus, grows quickly on routine
bacteriology media, if present in large numbers. Furthermore, pathological
confirmation of invasive disease is usually required to make a definitive
diagnosis. Consider fungal cultures for optimal detection of dimorphic fungi
(e.g., Histoplasma, Coccidiodies) and Cryptococcus in the appropriate clinical
context.
Note: yeast, also detected readily by routine bacteriology culture, are rarely
a cause of pneumonia, and likely represent colonization or contamination.
