Culture, Bacterial, Throat or Nasopharyngeal

Culture, Bacterial, Throat or Nasopharyngeal

Synonym/acronym: Routine throat culture.

Common use

To identify pathogenic bacterial organisms in the throat and nares as an indicator for appropriate therapeutic interventions. Treat infections such as pharyngitis, thrush, strep throat, and screen for methicillin-resistant Staphylococcus aureus (MRSA).

Specimen

Throat or nasopharyngeal swab.

Normal findings

(Method: Aerobic culture) No growth.

Description

The routine throat culture is a commonly ordered test to screen for the presence of group A bβ-hemolytic streptococci. Streptococcus pyogenes is the gram-positive organism that most commonly causes acute pharyngitis. The more dangerous sequelae of scarlet fever, rheumatic heart disease, and glomerulonephritis are less frequently seen because of the early treatment of infection at the pharyngitis stage. There are a number of other bacterial agents responsible for pharyngitis. Specific cultures can be set up to detect other pathogens such as Bordetella (gram negative), Corynebacteria (gram positive), Haemophilus (gram negative), or Neisseria (gram negative) if they are suspected or by special request from the health-care provider (HCP). Corynebacterium diphtheriae is the causative agent of diphtheria. Neisseria gonorrhoeae is a sexually transmitted pathogen. In children, a positive throat culture for Neisseria usually indicates sexual abuse. The laboratory will initiate antibiotic sensitivity testing if indicated by test results. Sensitivity testing identifies the antibiotics to which the organisms are susceptible to ensure an effective treatment plan.

This procedure is contraindicated for

  • high alertPatients with epiglottitis. In cases of acute epiglottitis, the throat culture may need to be obtained in the operating room or other appropriate location where the required emergency equipment and trained personnel can safely perform the procedure.

Indications

  • Assist in the diagnosis of bacterial infections such as tonsillitis, diphtheria, gonorrhea, or pertussis
  • Assist in the diagnosis of upper respiratory infections resulting in bronchitis, pharyngitis, croup, and influenza
  • Isolate and identify group A β-hemolytic streptococci as the cause of strep throat, acute glomerulonephritis, scarlet fever, or rheumatic fever

Potential diagnosis

Reports on cultures that are positive for group A β-hemolytic streptococci are generally available within 24 to 48 hr. Cultures that report on normal respiratory flora are issued after 48 hr. Culture results of no growth for Corynebacterium require 72 hr to report; 48 hr are required to report negative Neisseria cultures.

Critical findings

  • Culture: Growth of Corynebacterium or MRSA

  • Note and immediately report to the HCP positive results and related symptoms.

  • It is essential that a critical finding be communicated immediately to the requesting 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

Pretest

  • 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. Address concerns about pain and explain that there may be some discomfort during the specimen collection. The time it takes to collect a proper specimen varies according to the level of cooperation of the patient. Inform the patient that specimen collection takes approximately 5 min.
  • Note that there are no food or fluid restrictions unless by medical direction.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.

Intratest

  • Potential complications:

  • In cases of epiglottitis, do not swab the throat. This can cause a laryngospasm resulting in a loss of airway. Symptoms associated with epiglottitis include sore throat, difficulty swallowing, difficulty breathing (related to blocked airway), blue skin (especially around the lips), confusion, irritability, and sluggishness (related to decreased oxygen levels). Potential interactions include stabilizing the airway, monitoring vital signs, and administering the appropriate medications which may include antibiotics. Antibiotics may be administered before the results of the culture are obtained.

  • Ensure that the patient has complied with medication restrictions prior to the procedure.
  • Have emergency equipment readily available. Keep resuscitation equipment on hand in case of respiratory impairment or laryngospasm after the procedure.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate collection containers 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).
  • To collect the throat culture, tilt the patient’s head back. Swab both tonsillar pillars and oropharynx with the sterile Culturette. A tongue depressor can be used to ensure that contact with the tongue and uvula is avoided.
  • A nasopharyngeal specimen is collected through the use of a flexible probe inserted through the nose and directed toward the back of the throat.
  • Place the swab in the Culturette tube and squeeze the bottom of the Culturette tube to release the liquid transport medium. Ensure that the end of the swab is immersed in the liquid transport medium.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • 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 usual medication as directed by the HCP.
  • Instruct the patient to notify the HCP immediately if difficulty in breathing or swallowing occurs or if bleeding occurs.
  • Instruct the patient to perform mouth care after the specimen has been obtained.
  • Provide comfort measures and treatment such as antiseptic gargles; inhalants; and warm, moist applications as needed. A cool beverage may aid in relieving throat irritation caused by coughing or suctioning.
  • 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: Dehydration can been seen in patients with a bacterial throat infection due to pain with swallowing. Pain medications reduce patient’s dysphagia and allow for adequate intake of fluids and foods.
  • 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. Emphasize the importance of reporting continued signs and symptoms of the infection. Provide information regarding vaccine-preventable diseases where indicated (e.g., diphtheria H1N1 flu, Haemophilus influenza, seasonal influenza, pneumococcal disease). Provide contact information, if desired, for the Centers for Disease Control and Prevention (www.cdc.gov/vaccines/vpd-vac). Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed 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 CBC, Gram stain, and group A streptococcal (rapid) screen.
  • Refer to the Immune and Respiratory systems tables at the end of the book for related tests by body system.