Culture and Smear, Mycobacteria

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Culture and Smear, Mycobacteria

Synonym/acronym: Acid-fast bacilli (AFB) culture and smear, tuberculosis (TB) culture and smear, Mycobacterium culture and smear.

Common use

To assist in the diagnosis of tuberculosis.


Sputum (5 to 10 mL), bronchopulmonary lavage, tissue, material from fine-needle aspiration, bone marrow, cerebrospinal fluid (CSF), gastric aspiration, urine, and stool.

Normal findings

(Method: Culture on selected media, microscopic examination of sputum by acid-fast or auramine-rhodamine fluorochrome stain) Rapid methods include: chemiluminescent-labeled DNA probes that target ribosomal RNA of the Mycobacterium radiometric carbon dioxide detection from 14C-labeled media, polymerase chain reaction/amplification techniques.
  • Culture: No growth
  • Smear: Negative for AFB
  • Rapid Testing Method:Mycobacterium


A culture and smear test is used primarily to detect Mycobacterium tuberculosis, which is a tubercular bacillus. The cell wall of this mycobacterium contains complex lipids and waxes that do not take up ordinary stains. Cells that resist decolorization by acid alcohol are termed acid-fast.There are only a few groups of acid-fast bacilli (AFB); this characteristic is helpful in rapid identification so that therapy can be initiated in a timely manner. Smears may be negative 50% of the time even though the culture develops positive growth 3 to 8 wk later. AFB cultures are used to confirm positive and negative AFB smears. M. tuberculosis grows in culture slowly.Automated liquid culture systems, such as the Bactec and MGIT (Becton Dickinson and Company, 1 Becton Drive, Franklin Lakes, NJ, 07417), have a turnaround time of approximately 10 days. Results of tests by polymerase chain reaction culture methods are available in 24 to 72 hr.The QuantiFERON-TB Gold (QFT-G), QuantiFERON-TB Gold In-Tube (QFT-GIT), and T-SPOT interferon release blood tests are approved by the U.S. Food and Drug Administration for all applications in which the TB skin test is used.The blood test is a procedure in which a sample of whole blood from the patient is incubated with a reagent cocktail of peptides known to be present in individuals infected by Mycobacterium tuberculosis but not found in the blood of previously vaccinated individuals or individuals who do not have the disease.The blood test offers the advantage of eliminating many of the false reactions encountered with skin testing, only a single patient visit is required, and results can be available within 24 hr. The blood tests and skin tests are approved as indirect tests for Mycobacterium tuberculosis, and the Centers for Disease Control and Prevention (CDC) recommends their use in conjunction with risk assessment, chest x-ray, and other appropriate medical and diagnostic evaluations. Detailed information is found in the monograph titled “Tuberculosis: Skin and Blood Tests.”

M. tuberculosis is transmitted via the airborne route to the lungs. It causes areas of granulomatous inflammation, cough, fever, and hemoptysis. It can remain dormant in the lungs for long periods. The incidence of tuberculosis has increased since the late 1980s in depressed inner-city areas, among prison populations, and among HIV-positive patients. Of great concern is the increase in antibiotic-resistant strains. HIV-positive patients often become ill from concomitant infections caused by M. tuberculosis and Mycobacterium avium intracellulare. M. avium intracellulare is acquired via the gastrointestinal tract through ingestion of contaminated food or water.The organism’s waxy cell wall protects it from acids in the human digestive tract. Isolation of mycobacteria in the stool does not mean the patient has tuberculosis of the intestines because mycobacteria in stool are most often present in sputum that has been swallowed.

This procedure is contraindicated for



  • Assist in the diagnosis of mycobacteriosis.
  • Assist in the diagnosis of suspected pulmonary tuberculosis secondary to AIDS.
  • Assist in the differentiation of tuberculosis from carcinoma or bronchiectasis.
  • Investigate suspected pulmonary tuberculosis.
  • Monitor the response to treatment for pulmonary tuberculosis.

Potential diagnosis

Identified OrganismPrimary Specimen SourceCondition
Mycobacterium avium intracellulareCSF, lymph nodes, semen, sputum, urineOpportunistic pulmonary infection
M. fortuitumBone, body fluid, sputum, surgical wound, tissueOpportunistic infection (usually pulmonary)
M. lepraeCSF, skin scrapings, lymph nodesHanson’s disease (leprosy)
M. kansasiiJoint, lymph nodes, skin, sputumPulmonary tuberculosis
M. marinumJointGranulomatous skin lesions
M. tuberculosisCSF, gastric washing, sputum, urinePulmonary tuberculosis
M. xenopiSputumPulmonary tuberculosis

Critical findings

  • Smear: Positive for AFB
  • Rapid Testing Method: Positive for Mycobacterium
  • Culture: Growth of pathogenic bacteria
  • Note and immediately report to the health-care provider (HCP) positive results and related symptoms.

  • 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

  • Specimen collection after initiation of treatment with antituberculosis drug therapy may result in inhibited or no growth of organisms.
  • Contamination of the sterile container with organisms from an exogenous source may produce misleading results.
  • Specimens received on a dry swab should be rejected:A dry swab indicates that the sample is unlikely to have been collected properly or unlikely to contain a representative quantity of significant organisms for proper evaluation.
  • Inadequate or improper (e.g., saliva) samples should be rejected.
  • Failure to follow dietary restrictions before the procedure may cause the procedure to be canceled or repeated.

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 diagnosing respiratory disease.
  • 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 exposure to tuberculosis.
  • 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 procedures 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 sputum specimen is collected 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 suction. 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. Inform the patient that the culture results will not be reported for 3 to 8 wk.
  • 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 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.
  • Note that there are no food or fluid restrictions 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 restrictionsprior 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.
  • Assist the patient to a comfortable position, and direct the patient to breathe normally during the beginning of the local 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 collection container 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).
  • 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. If leprosy is suspected, obtain a smear from nasal scrapings or a biopsy specimen from lesions in a sterile container.
  • 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.
  • 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. 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, blood gases, bronchoscopy, chest x-ray, complete blood count, CT thoracic, cultures (fungal, sputum, throat, viral), cytology sputum, gallium scan, Gram stain, lung perfusion scan, lung ventilation scan, MRI chest, mediastinoscopy, pleural fluid analysis, pulmonary function tests, 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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