Sputum culture

Microbiology

• Sputum culture results are often unreliable and sensitivity of culture is poor for many pathogens. Culture results may reflect colonisation rather than true infection. Results should be interpreted in conjunction with the clinical findings.
• ET secretions are treated in the same was as a sputum sample.
• Bronchiectasis samples are examined for a wider range of respiratory pathogens, i.e. those indicative of chronic infection
• See also:
  • Legionella antigen in urine
  • Pneumococcal antigen in urine
  • Mycobacterium and TB investigations
  • Bronchoalveolar lavage (BAL)
  • Pneumocystis jirovecii (PCP) investigation
  • Cystic fibrosis (CF) screen
  • Respiratory viruses

Sample requirements

60 mL wide-mouthed container

The material required is from the lower respiratory tract, expectorated by deep coughing.

When the cough is dry, physiotherapy, postural drainage or inhalation of an aerosol before expectoration may be helpful.

Expectorate sample directly into the container. Ideally a minimum volume of 1 mL is required.

Saliva and pernasal secretions are not suitable.

Multiple samples (i.e. 3 consecutive daily samples) are NOT required for routine sputum culture.

Required information

• Current or recent antibiotic therapy
• If sample is induced sputum
• Bronchiectasis
• Immunocompromise
• Travel history
• Occupational risks

Storage/transport

Transport without delay to ensure survival of fastidious organisms. Where transport is difficult, specimens may be cultured up to 48hr after collection.

If specimens are not processed on the same day as they are collected, interpretation of results should be made with care.

If transport is delayed, refrigeration is preferable to storage at ambient temperature.

Turnaround time

2 - 5 days