Sputum Culture (and an Overview of Culture Tests)
Definition
Detects the bacteria or fungi causing a respiratory tract infection. Sputum is a type of thick mucus produced in your lungs.
Sample collection: The patient coughs deeply and spits into a container. If not enough sputum can be produced, saline mist may be given, or a sample may be taken from the airway by bronchoscopy using a small brush or suction.
Purpose
For symptoms of a serious lung or respiratory tract infection: persistent cough, fever, chills, shortness of breath, chest pain, fatigue or confusion. It is also ordered when imaging shows findings suggestive of infection.
Results
⏱Turnaround time: Depending on which bacteria are being grown, it may take from a few days to weeks. This is inherent to culture tests, as the microorganism must be allowed to grow.
- Normal: No harmful bacteria or fungi grew
- Abnormal: Bacterial or fungal infection, pneumonia, bronchitis, tuberculosis, or a flare-up of a chronic disease such as cystic fibrosis or COPD
Risks and Limitations
Two critical points:
1. Prior antibiotic use affects bacterial growth and can mislead the result, so the culture should be collected before antibiotics are started whenever possible 2. Sample quality is decisive, it depends on obtaining adequate sputum, not just saliva. A sample consisting of saliva is invalid
Relationship to the antibiogram: The microorganism grown in culture is then subjected to antibiotic susceptibility testing (antibiogram), which is how the effective antibiotic is determined (see the Antibiogram entry).
AdaGen's other culture tests (throat, abscess, semen, wound, ear discharge, stool, urine, AF genital, urethral discharge, vaginal) work on the same principle: the sample is collected, the microorganism is grown, identified and sent for an antibiogram. The sample type changes, the method is the same.