Sputum Culture


Bacteriologic examination of sputum – material raised from the lungs and bronchi during deep coughing – is an important aid in managing lung disease. The usual method of specimen collection is expectoration. Other methods include tracheal suctioning and bronchoscopy. A gram stain of expectorated sputum must be examined to ensure that it’s representative of secretions from the lower respiratory tract rather than contaminated by oral flora. Careful examination of an acid-fast sputum smear may provide presumptive evidence of a mycobacterial infection, such as tuberculosis.

Sputum may be cultured to identify respiratory pathogens. Expectoration, the usual sputum collection method, may require ultrasonic nebulization, hydration, or chest percussion and postural drainage. Less common method include tracheal suctioning where in it provides a more reliable diagnostic specimen but generally isn’t used, unless expectoration fails to provide sample.

  • To isolate and identify causes of pulmonary infections.
  • To aid diagnosis of respiratory diseases, such as bronchitis, tuberculosis, lung abscess, and pneumonia.
  1. Inform the patient that his test requires a sputum specimen.
  2. Explain that the specimens may be collected on at least three consecutive mornings if the suspected organism is Myobacterium Tuberculosis.
  3. Inform the patient that result for TB cultures take up to 2 months.
  1. Put on gloves and a mask.
  2. Instruct the patient to cough deeply and expectorate into the container.
  3. If the cough in nonproductive, use chest physiotherapy or nebulization to induce sputum, as ordered.
  4. Using aseptic technique, close the container securely and place it in a leak proof bag before sending it to the laboratory.
Tracheal Suctioning
  1. Give oxygen to the patient before and after the procedure as necessary.
  2. Attach the sputum trap to suction catheter.
  3. Lubricate the catheter with normal saline solution and pass the catheter through the nostril without suction.
  4. Advance the catheter into the trachea; apply suction while withdrawing the catheter, not during catheter insertion.
  5. Suction only for 5 to 10 seconds at a time.
  6. Stop suction and remove the catheter.
  7. Discard the catheter in the proper receptacle.
  8. Detach the in-line sputum trap from the suction apparatus and cap the opening.
  9. During the passage through the throat and oropharynx, sputum specimens are commonly contaminated with indigenous bacterial flora.
  10. Label the container with the patient’s name, the nature and origin of the specimen, the date and time of collection, the initial diagnosis, and any current antimicrobial therapy.
  11. Send the specimen to the laboratory immediately after collection.
Nursing Interventions
  1. Provide mouth care to the patient.
  2. Monitor his vital signs and respiratory status.
  3. Monitor oxygen saturation with a pulse oximeter.
  4. If the patient becomes hypoxic or cyanotic during suctioning, remove the catheter immediately and give oxygen while suctioning pulse oximetry.
Normal Results
  1. Common flora includes alpha-hemolytic streptococci. Neisseria, and diptheroid.
  2. Presence of common flora doesn’t rule out infection.
Abnormal Results
  1. Because sputum is invariably contaminated with normal oropharyngeal flora, a culture isolate must be interpreted in light of the patient’s overall clinical condition.
  2. Isolation of Myobacterium Tuberculosis suggests tuberculosis.
  3. Isolation of pathogenic organisms most often includes Streptococcus pneumonia, Myobacterium Tuberculosis, Klebsiella pneumoniae (and other Enterobacteriaceae), Haemophilus influenzae, Staphyloccocus aureus, and Pseudomonas aeruginosa.
  • Hypoxemia
  • Cardiac arrhythmias
  • Laryngospasm
  • Bronchospasm
  • Pneumothorax
  • Perforation of the trachea or bronchus
  • Trauma to repiratory structures
  • Bleeding
Interfering Factors
  • Contaminated or inadequate sample.