Culture, Bacterial, Sputum

Culture, Bacterial, Sputum

Synonym/acronym: Routine culture of sputum.

Common use

To identify pathogenic bacterial organisms in the sputum as an indicator for appropriate therapeutic interventions for respiratory infections.


Sputum (10 to 15 mL).

Normal findings

(Method: Aerobic culture on selective and enriched media; microscopic examination of sputum by Gram stain.) The presence of normal upper respiratory tract flora should be expected. Tracheal aspirates and bronchoscopy samples can be contaminated with normal flora, but transtracheal aspiration specimens should show no growth. Normal respiratory flora include Neisseria catarrhalis,Candida albicans, diphtheroids, α-hemolytic streptococci, and some staphylococci. The presence of normal flora does not rule out infection. A normal Gram stain of sputum contains polymorphonuclear leukocytes, alveolar macrophages, and a few squamous epithelial cells.


This test involves collecting a sputum specimen so the pathogen can be isolated and identified. The test results will reflect the type and number of organisms present in the specimen as well as the antibiotics to which the identified pathogenic organisms are susceptible. Sputum collected by expectoration or suctioning with catheters and by bronchoscopy cannot be cultured for anaerobic organisms; instead, transtracheal aspiration or lung biopsy must be used. The laboratory will initiate antibiotic sensitivity testing if indicated by test results. Sensitivity testing identifies antibiotics to which the organisms are susceptible to ensure an effective treatment plan.

This procedure is contraindicated for




  • Assist in the diagnosis of respiratory infections, as indicated by the presence or absence of organisms in culture
  • Gram Stain

  • Assist in the differentiation of gram-positive from gram-negative bacteria in respiratory infection
  • Assist in the differentiation of sputum from upper respiratory tract secretions, the latter being indicated by excessive squamous cells or absence of polymorphonuclear leukocytes

Potential diagnosis

The major difficulty in evaluating results is in distinguishing organisms infecting the lower respiratory tract from organisms that have colonized but not infected the lower respiratory tract. Review of the Gram stain assists in this process. The presence of greater than 25 squamous epithelial cells per low-power field (lpf) indicates oral contamination, and the specimen should be rejected. The presence of many polymorphonuclear neutrophils and few squamous epithelial cells indicates that the specimen was collected from an area of infection and is satisfactory for further analysis. Bacterial pneumonia can be caused by Streptococcus pneumoniae,Haemophilus influenzae, staphylococci, and some gram-negative bacteria. Other pathogens that can be identified by culture are Corynebacterium diphtheriae,Klebsiella pneumoniae, and Pseudomonas aeruginosa. Some infectious agents, such as C. diphtheriae, are more fastidious in their growth requirements and cannot be cultured and identified without special treatment. Suspicion of infection by less commonly identified and/or fastidious organisms must be communicated to the laboratory to ensure selection of the proper procedure required for identification.

Critical findings

  • C. diphtheriae
  • Legionella
  • Note and immediately report to the health-care provider (HCP) positive results for bacterial pathogens or parasites.

  • It is essential that a critical finding be communicated immediately to the requesting health-care provider (HCP). Lists of specific organisms may vary among facilities; specific organisms are required to be reported to local, state, and national departments of health.

  • Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.

Interfering factors

  • Contamination with oral flora may invalidate results.
  • Specimen collection after antibiotic therapy has been initiated may result in inhibited or no growth of organisms.

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in identification of the organism causing infection.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s immune and respiratory systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Note any recent medications that can interfere with test results.
  • Review the procedure with the patient. Reassure the patient that he or she will be able to breathe during the procedure if specimen collection is accomplished via suction method. Ensure that oxygen has been administered 20 to 30 min before the procedure if the specimen is to be obtained by tracheal suctioning. Address concerns about pain related to the procedure. Atropine is usually given before bronchoscopy examinations to reduce bronchial secretions and prevent vagally induced bradycardia. Meperidine (Demerol) or morphine may be given as a sedative. Lidocaine is sprayed in the patient’s throat to reduce discomfort caused by the presence of the tube.
  • Explain to the patient that the time it takes to collect a proper specimen varies according to the level of cooperation of the patient and the specimen collection site. Emphasize that sputum and saliva are not the same. Inform the patient that multiple specimens may be required at timed intervals.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Bronchoscopy

  • Make sure a written and informed consent has been signed prior to the bronchoscopy/biopsy procedure and before administering any medications.
  • Other than antimicrobial drugs, there are no medication restrictions, unless by medical direction.
  • Instruct the patient that to reduce the risk of nausea and vomiting, solid food and milk or milk products have been restricted for at least 8 hr, and clear liquids have been restricted for at least 2 hr prior to general anesthesia, regional anesthesia, or sedation/analgesia (monitored anesthesia). The American Society of Anesthesiologists has fasting guidelines for risk levels according to patient status. More information can be located at Patients on beta blockers before the surgical procedure should be instructed to take their medication as ordered during the perioperative period. Protocols may vary among facilities.
  • Expectorated Specimen

  • Additional liquids the night before may assist in liquefying secretions during expectoration the following morning.
  • Assist the patient with oral cleaning before sample collection to reduce the amount of sample contamination by organisms that normally inhabit the mouth.
  • Instruct the patient not to touch the edge or inside of the container with the hands or mouth.
  • Other than antimicrobial drugs, there are no medication restrictions, unless by medical direction.
  • There are no food or fluid restrictions, unless by medical direction.
  • Tracheal Suctioning

  • Assist in providing extra fluids, unless contraindicated, and proper humidification to decrease tenacious secretions. Inform the patient that increasing fluid intake before retiring on the night before the test aids in liquefying secretions and may make it easier to expectorate in the morning. Also explain that humidifying inspired air also helps liquefy secretions.
  • Other than antimicrobial drugs, there are no medication restrictions, unless by medical direction.
  • There are no food or fluid restrictions, unless by medical direction.
  • If the specimen is collected by expectoration or tracheal suctioning, there are no food, fluid, or medication restrictions (except antibiotics), unless by medical direction.


  • Potential complications:
  • Complications associated with bronchoscopy are rare but may include bleeding, bronchial perforation, bronchospasm, infection, laryngospasm, and pneumothorax.

  • Ensure that the patient has complied with dietary and medication restrictions prior to the bronchoscopy procedure.
  • Have patient remove dentures, contact lenses, eyeglasses, and jewelry. Notify the HCP if the patient has permanent crowns on teeth. Have the patient remove clothing and change into a gown for the procedure.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Have emergency equipment readily available. Keep resuscitation equipment on hand in case of respiratory impairment or laryngospasm after the procedure.
  • Avoid using morphine sulfate in patients with asthma or other pulmonary disease. This drug can further exacerbate bronchospasms and respiratory impairment.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Assist the patient to a comfortable position and direct the patient to breathe normally during the beginning of the general anesthesia and to avoid unnecessary movement during the local anesthetic and the procedure. Instruct the patient to cooperate fully and to follow directions.
  • Observe standard precautions and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate tubes with the corresponding patient demographics, date and time of collection, and any medication the patient is taking that may interfere with test results (e.g., antibiotics). Collect the specimen in the appropriate sterile collection container.
  • Bronchoscopy

  • Record baseline vital signs.
  • The patient is positioned in relation to the type of anesthesia being used. If local anesthesia is used, the patient is seated and the tongue and oropharynx are sprayed and swabbed with anesthetic before the bronchoscope is inserted. For general anesthesia, the patient is placed in a supine position with the neck hyperextended. After anesthesia, the patient is kept in supine or shifted to a side-lying position and the bronchoscope is inserted. After inspection, the samples are collected from suspicious sites by bronchial brush or biopsy forceps.
  • Expectorated Specimen

  • Ask the patient to sit upright, with assistance and support (e.g., with an overbed table) as needed.
  • Ask the patient to take two or three deep breaths and cough deeply. Any sputum raised should be expectorated directly into a sterile sputum collection container.
  • If the patient is unable to produce the desired amount of sputum, several strategies may be attempted. One approach is to have the patient drink two glasses of water, and then assume the position for postural drainage of the upper and middle lung segments. Effective coughing may be assisted by placing either the hands or a pillow over the diaphragmatic area and applying slight pressure.
  • Another approach is to place a vaporizer or other humidifying device at the bedside. After sufficient exposure to adequate humidification, postural drainage of the upper and middle lung segments may be repeated before attempting to obtain the specimen.
  • Other methods may include obtaining an order for an expectorant to be administered with additional water approximately 2 hr before attempting to obtain the specimen. Chest percussion and postural drainage of all lung segments may also be employed. If the patient is still unable to raise sputum, the use of an ultrasonic nebulizer (“induced sputum”) may be necessary; this is usually done by a respiratory therapist.
  • Tracheal Suctioning

  • Obtain the necessary equipment, including a suction device, suction kit, and Lukens tube or in-line trap.
  • Position the patient with head elevated as high as tolerated.
  • Put on sterile gloves. Maintain the dominant hand as sterile and the nondominant hand as clean.
  • Using the sterile hand, attach the suction catheter to the rubber tubing of the Lukens tube or in-line trap. Then attach the suction tubing to the male adapter of the trap with the clean hand. Lubricate the suction catheter with sterile saline.
  • Tell nonintubated patients to protrude the tongue and to take a deep breath as the suction catheter is passed through the nostril. When the catheter enters the trachea, a reflex cough is stimulated; immediately advance the catheter into the trachea and apply suction. Maintain suction for approximately 10 sec, but never longer than 15 sec. Withdraw the catheter without applying suction. Separate the suction catheter and suction tubing from the trap, and place the rubber tubing over the male adapter to seal the unit.
  • 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. The patient should be hyperoxygenated before and after the procedure in accordance with standard protocols for suctioning these patients.
  • Generally, a series of three to five early morning sputum samples are collected in sterile containers.
  • General

  • Monitor the patient for complications related to the procedure (e.g., allergic reaction, anaphylaxis, bronchospasm).
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Instruct the patient to resume preoperative diet, as directed by the HCP. Assess the patient’s ability to swallow before allowing the patient to attempt liquids or solid foods.
  • Inform the patient that he or she may experience some throat soreness and hoarseness. Instruct patient to treat throat discomfort with lozenges and warm gargles when the gag reflex returns.
  • Monitor vital signs and compare with baseline values every 15 min for 1 hr, then every 2 hr for 4 hr, and then as ordered by the HCP. Monitor temperature every 4 hr for 24 hr. Notify the HCP if temperature is elevated. Protocols may vary among facilities.
  • Emergency resuscitation equipment should be readily available if the vocal cords become spastic after intubation.
  • Observe for delayed allergic reactions, such as rash, urticaria, tachycardia, hyperpnea, hypertension, palpitations, nausea, or vomiting.
  • Observe the patient for hemoptysis, difficulty breathing, cough, air hunger, excessive coughing, pain, or absent breathing sounds over the affected area. Report any symptoms to the HCP.
  • Evaluate the patient for symptoms indicating the development of pneumothorax, such as dyspnea, tachypnea, anxiety, decreased breathing sounds, or restlessness. A chest x-ray may be ordered to check for the presence of this complication.
  • Evaluate the patient for symptoms of empyema, such as fever, tachycardia, malaise, or elevated white blood cell count.
  • Administer antibiotic therapy if ordered. Remind the patient of the importance of completing the entire course of antibiotic therapy, even if signs and symptoms disappear before completion of therapy.
  • Nutritional Considerations: Malnutrition is commonly seen in patients with severe respiratory disease for numerous reasons including fatigue, lack of appetite, and gastrointestinal distress. Adequate intake of vitamins A and C are also important to prevent pulmonary infection and to decrease the extent of lung tissue damage.
  • Recognize anxiety related to test results. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Instruct the patient to use lozenges or gargle for throat discomfort. Inform the patient of smoking cessation programs as appropriate. The importance of following the prescribed diet should be stressed to the patient/caregiver. Educate the patient regarding access to counseling services, as appropriate. Provide information regarding vaccine preventable diseases where indicated (e.g., H1N1 flu, Haemophilus influenzae, seasonal influenza, pertussis, pneumococcal disease). Provide contact information, if desired, for the Centers for Disease Control and Prevention ( Answer any questions or address any concerns voiced by the patient or family.
  • Instruct the patient in the use of any ordered medications. Explain the importance of adhering to the therapy regimen. As appropriate, instruct the patient in significant side effects and systemic reactions associated with the prescribed medication. Encourage him or her to review corresponding literature provided by a pharmacist.
  • Depending on the results of this procedure, additional testing may be needed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include antibodies, anti–glomerular basement membrane, arterial/alveolar oxygen ratio, biopsy lung, blood gases, bronchoscopy, chest x-ray, CBC, CT thoracic, culture (fungal, mycobacterium, throat, viral), cytology sputum, gallium scan, Gram stain/acid-fast stain, HIV-1/2 antibodies, lung perfusion scan, lung ventilation scan, MRI chest, mediastino-scopy, pleural fluid analysis, PFT, and TB tests.
  • Refer to the Immune and Respiratory systems tables at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners
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