Synonym

• C+S (Sputum)
• Culture & Sensitivity (Sputum)

Tubes

• 5-10 mL of sputum in a sterile screw-cap container / orange cap sterile container
• Early morning specimens by expectoration OR by induced sputum, chest physiotherapy, nasotracheal or tracheal suctioning, or bronchoscopy, to obtain sputum

Additional information

• Sputum collection:
• The patient should remove dentures, brush teeth, rinse mouth well (without toothpaste or mouth gargle), and clear the nose and throat before collection of sample
• Instruct the patient to take 2-3 deep breaths, and cough deeply and expectorate into the container
• The specimen should be examined to make sure it contains a sufficient quantity of thick mucus, and not saliva
• Avoid postnasal secretions or saliva
• If cough is nonproductive, use chest physiotherapy, aerosol spray, or nebulization to induce sputum
• The patient is instructed to drink 2 glasses of water and sit in the position for postural drainage of the upper and middle lung segments. Placing either the hands or a pillow over the diaphragmatic area and applying slight pressure may assist effective coughing
• Sufficient exposure to vaporizer or a humidifying device followed by postural drainage of the upper and middle lung segments may assist effective coughing
• The patient is instructed to take an expectorant with additional water, 2 hrs prior to obtaining the specimen
• The patient is asked to breathe aerosolized droplets of a sodium chloride-glycerin solution until a strong cough reflex is initiated
• Ultrasonic nebulizers may be used for sputum induction with the help of respiratory therapist
• Tracheal suctioning:
• Consult the physician before obtaining the suctioned sample
• Administer high flow oxygen to patient before and after the procedure if necessary
• Position the patient with head elevated as high as tolerated
• Attach sputum trap to suction catheter. Using sterile gloves, lubricate catheter with normal saline solution, and pass it through patient's nostril without suction (patient will cough when catheter passes through larynx). Advance catheter into the trachea
• Apply suction for 10 seconds, but never longer than 15 seconds
• Withdraw the catheter without applying suction
• For intubated patients or patients with a tracheostomy, the previous procedure is followed, except that the suction catheter is passed through the existing endotracheal or tracheostomy tube rather than through the nostril
• Suctioning is contraindicated in patients with esophageal varices
• Bronchoscopy:
• A local anesthetic is sprayed into patient's throat or patient gargles with local anesthetic
• Insert bronchoscope through pharynx and trachea into bronchus
• After inspection, the samples are collected from suspicious sites by bronchial brush or by aspiration with irrigation such as normal saline if required
• After obtaining specimen, remove bronchoscope
• During and after bronchoscopy, observe patient carefully for signs of
• Hypoxemia
• Laryngospasm (laryngeal stridor)
• Bronchospasm (paroxysms of coughing or wheezing)
• Pneumothorax (dyspnea, cyanosis, pleural pain, tachycardia)
• Perforation of trachea or bronchus (Subcutaneous crepitus)
• Trauma to respiratory structures (blood-tinged sputum, coughing up blood)
• Also, check for difficulty breathing or swallowing
• Don't give liquids until gag reflex returns
• 3 consecutive morning specimens are required if requested for Mycobacterium tuberculosis culture detection
• Label the collection container properly including nature and origin of specimen with date and time of collection
• Do not refrigerate specimens
• Send specimen immediately to the laboratory

Info

• Sputum culture is performed to isolate and identify the pathogenic microorganisms causing lung infections, and is followed by sensitivity testing to identify the antimicrobials sensitive to the organisms from the sputum
• Sputum is a secretion that is produced in the pulmonary bronchi. It is not secreted from the postnasal region, and is not spittle or saliva
• There is debate among clinicians regarding the clinical value of this test in non-complicated patients with lower respiratory infections

Clinical

• Sputum culture and sensitivity may be indicated in the following conditions:
• As an aid in the diagnosis of respiratory diseases as indicated by the presence or absence of organisms in culture, which include:
• Pneumonia (Bacterial, Viral, Atypical)
• Pulmonary TB
• Chronic bronchitis
• Bronchiectasis
• Suspected pulmonary mycotic infections
• Lung abscess
• In persons presenting with productive cough and sputum
• To monitor the progress and therapeutic efficacy of treatment for lower respiratory tract infections
• To assess the antimicrobials sensitive to the causative organisms of pulmonary infections
• Common potential pathogenic organisms which can be detectable on sputum culture include:
• Streptococcus pneumoniae
• Haemophilus influenzae
• Moraxella catarrhalis
• Beta-hemolytic streptococci
• Bordetella pertussis
• Klebsiella sp.
• Mycobacterium sp.
• Pseudomonas aeruginosa
• Staphylococcus aureus
• Less common potential pathogenic organisms which can be detectable on sputum culture include:
• Blastomyces dermatitidis
• Candida albicans
• Corynebacterium diphtheriae
• Coccidioides immitis
• Escherichia coli
• Francisella tularensis
• Histoplasma capsulatum
• Neisseria meningitides
• Pneumocystis
• Yersinia pestis
• Viral causes of pneumonia (will not show growth on sputum culture) include:
• Adenoviruses
• Cytomegalovirus
• Hantavirus
• Herpes simplex viruses
• Influenza viruses
• Parainfluenza virus
• Respiratory syncytial virus
• Rhinovirus
• SARS (SARS associated Coronavirus)
• Varicella zoster virus
• Normal flora of respiratory tract includes
• Alpha-hemolytic streptococci
• Staphylococcus saprophyticus
• Diphtheroids
• Neisseria catarrhalis
• Candida albicans
• Common nosocomial infections detected on sputum culture include
• Staphylococcus aureus (Including MRSA)
• Pseudomonas
• Klebsiella
• Routine respiratory cultures will not detect:
• Chlamydia species
• Coxiella burnetti
• Legionella species
• Mycobacterium tuberculosis
• Mycoplasma pneumoniae
• Viral pathogens

Additional information

• Sputum culture results must be interpreted in the context of the patient's clinical condition; Sputum is often contaminated with normal oropharyngeal flora
• Evaluation of expectorated sputum specimens with Gram stain to determine the acceptability of a specimen for bacterial culture
• The presence of >25 squamous epithelial cells/low-power field (lpf) indicates oral contamination (specimen to be rejected)
• The presence of many polymorphonuclear neutrophils, alveolar macrophages, and few squamous epithelial cells indicates that the specimen was collected from an area of infection (satisfactory)
• Sputum collected by expectoration or suctioning with catheters and by bronchoscopy cannot be cultured for anaerobic organisms
• Factors interfering with test results include:
• Recent antimicrobial therapy
• Improper collection technique
• Collection over extended period (which may cause pathogens to deteriorate or become overgrown by commensals)
• ‘Dry' specimens i.e., saliva samples without actual sputum or contaminated with oral flora
• High concentration of sputum inducer (>20% propylene glycol with water) inhibits growth of M. tuberculosis
• Sample not sent to lab immediately
• Use of mouthwash before collecting a sputum sample
• Related laboratory tests include
• Arterial blood gas
• Chest x-ray
• Complete blood count
• Cytology of sputum

Nl Result

• Normal: Negative or Normal oral flora

High Result

A positive result on culture must be placed within the context of the patient's clinical status.

The result may relate to the causative organism or may be a contaminant.

References

• ARUP Laboratories®. Respiratory Culture. [Homepage on the internet]©2007. Last accessed on March 7, 2007. Available at URL: http://www.aruplab.com/guides/ug/tests/0060122.jsp
• Cao LD et al. Value of washed sputum gram stain smear and culture for management of lower respiratory tract infections in children. J Infect Chemother. 2004 Feb;10(1):31-6.
• da Silva RM et al. The clinical utility of induced sputum for the diagnosis of bacterial community-acquired pneumonia in HIV-infected patients: a prospective cross-sectional study. Braz J Infect Dis. 2006 Apr;10(2):89-93.
• eMedicine from WebMD®. Pneumonia, Bacterial. [Homepage on the Internet] ©1996-2006. Last updated on February 12, 2007. Last accessed on March 7, 2007. Available at URL: http://www.emedicine.com/MED/topic1852.htm
• Irfan S et al. Evaluation of a microcolony detection method and phage assay for rapid detection of Mycobacterium tuberculosis in sputum samples. Southeast Asian J Trop Med Public Health. 2006 Nov;37(6):1187-95.
• Laboratory Corporation of America. Lower Respiratory Culture. [Homepage on the internet]©2007. Last accessed on March 7, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/mb012000.htm
• Soler N et al. Bronchoscopic validation of the significance of sputum purulence in severe exacerbations of chronic obstructive pulmonary disease. Thorax. 2007 Jan;62(1):29-35. Epub 2006 Aug 23.
• van der Eerden MM et al. Value of intensive diagnostic microbiological investigation in low- and high-risk patients with community-acquired pneumonia. Eur J Clin Microbiol Infect Dis. 2005 Apr;24(4):241-9.