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Test ID: Sputum culture
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Sputum culture
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Culture of sputum for bacterial pathogens causing lower respiratory infections
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Useful For
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Diagnosis of lower respiratory bacterial infections including pneumonia
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Method name and description
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Conventional Culture Technique
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Clinical information
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Infections of the lower respiratory tract are a major cause of morbidity and mortality. Diagnosis of these infections frequently is complicated by the contamination of specimens with upper respiratory tract secretions during collection. Because the upper respiratory tract may be colonized with potential pathogens not involved in the infection of the lower tract and may yield organisms capable of inhibiting the bacteria involved in lower tract pathology, the laboratory should ensure that an appropriate specimen is processed.
The specimen must be microscopically examined both to assess its quality and to look for organisms associated with an inflammatory cell response.
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Aliases
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- Sputum culture
- Culture sputum
- C sputum
- Cystic fibrosis culture
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Specimen type / Specimen volume / Specimen container
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Specimen type:
- Sputum
- Cough swab from patients with cystic fibrosis or primary ciliary dyskinesia
Specimen volume:
- Ideally, a minimum volume of 1ml
Specimen container:
- Sterile leak proof container
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Collection instructions / Special Precautions / Timing of collection
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Collection instructions
- An expectorated deep cough sputum should be sent
Special precautions
- Avoid contamination with saliva
Timing of collection
- Before antimicrobial therapy.
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Relevant clinical information to be provided
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- Antimicrobial therapy
- Presence of pre-existing lung disease e.g. Cystic fibrosis, COPD, etc.and/or any other conditions predisposing to respiratory infections
- If aspiration pneumonia suspected
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Storage and transport instructions
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- Specimen should be transported to the laboratory at room temperature within 2 hrs
- If transport is delayed ≥ 2 hrs, then refrigerate at 2-8 C. The specimen should reach the laboratory within 24 hrs of collection.
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Specimen Rejection Criteria
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- Leaking container
- Salivary specimen
- Delayed specimen received >24 hrs of collection
- Duplicate specimen within 72 hrs
- No relevant clinical details provided with the request. (Please note that where applicable, the relevant clinical details should reflect those on the patient’s electronic record at the time the order was placed).
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Biological reference intervals and clinical decision values
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Negative Culture
- Normal upper respiratory flora isolated
- No growth
Positive Culture
- All clinically significant isolates are reported with antimicrobial susceptibilities
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Factors affecting test performance and result interpretation
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- Specimens mixed with saliva indicated by the presence of significant number of epithelial cells on microscopy. Such specimens are unlkely to represent lower respiratory tract pathology and are likely to be rejected
- Improper collection technique
- Improper container
- Improper transportation
- Improper processing
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Turnaround time / Days and times test performed / Specimen retention time
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Turnaround time:
- Microscopy: 24 hrs.
- Culture: 48-96hrs.
Days and times test performed:
- Daily 24/7. Note: this test is performed from Sunday to Friday 7am to 3pm in HGH microbiology laboratory.
Specimen retention time:
- 48 hrs. after the final report
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