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Sputum, Bronchial Washings and Throat Swabs

Many opportunistic mycoses have a pulmonary origin following the inhalation of fungal propagules.

Bronchial washings and sputa should be collected upon rising in the morning as overnight incubation and growth of fungi in the lungs will increase the likelihood of isolating pathogenic fungi. Patients should not eat before specimen collection. Twenty-four hour samples are unacceptable because they become overgrown with bacteria and fungal contaminants. It should also be stressed that bronchial washings and sputa will usually be contaminated with throat flora. For this reason interpretation of results may be difficult from poor quality specimens.

Throat specimens are obtained by rolling a moist sterile swab over the affected area. However, if Candida is suspected the affected area will need to be scraped with a sterile tongue depressor.

All specimens must be sent to the laboratory and processed as soon as possible, a delay of longer than two hours at room temperature may impede the detection of some fungi. Store at 4C if short delays in processing are anticipated.

Unless it is already sufficiently fluid to pipette with a Pasteur pipette, sputa may need to be emulsified by shaking with l2-20 sterile glass beads and about 3-5ml of sterile distilled water, depending on the volume of the original specimen. Any bits of blood, pus or necrotic material should be plated directly onto media.

  1. Make wet mount preparations in KOH (l drop) and Gram stained smears (l drop) of all suspicious areas. The PAS stain may be necessary if the KOH preparation is unsatisfactory.
  2. Inoculate sample onto:
    (a) Sabouraud's dextrose agar with chloramphenicol and gentamicin and incubate duplicate cultures at 26C and 35C; and
    (b) Brain heart infusion agar (BHIA) supplemented with 5% sheep blood and incubate at 35C. Maintain cultures for 4 weeks.
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Dr David Ellis
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