Throat Culture Procedure

Definition

A throat culture requires swabbing the throat, streaking a culture plate, and allowing the organisms to grow for isolation and identification of pathogens. A Gram-stained smear may provide preliminary identification, which may guide clinical management and determine the need for further tests. Culture reactions must be interpreted in light of clinical status, recent antimicrobial therapy, and the amount of normal flora.

image courtesy of : moondragon.org/

image courtesy of : moondragon.org/

Throat flora normally include nonhemolytic and alpha hemolytic streptococci, Neisseria species, staphylococci, diptheroids, some Haemophilus species, penumococci, yeats, enteric gram-negative organisms, spirochetes, Veillonella species, and Micrococcus species.

Purpose
  • To isolate and identify group A beta hemolytic streptococci.
  • To screen asymptomatic carriers of pathogens, especially Neisseria meningitides.
Procedure
Patient Preparation
  1. Confirm the patient’s identity using two patient identifiers according to facility policy.
  2. Explain to the patient that the throat culture is used to identify micro-organisms that may be causing his symptoms or to screen for asymptomatic carriers.
  3. Inform the patient that he doesn’t need to restrict food and fluids for the test.
  4. Advise the patient that a specimen will be collected from his throat. Describe the procedure, and warn him that he may gag during the swabbing.
  5. Check the patient’s history for recent antimicrobial therapy.
  6. Determine immunization history if it’s pertinent to the preliminary diagnosis.
Implementation
  1. Ask the patient to tilt his head back and close his eyes.
  2. With the throat well illuminated, check for inflamed areas, using a tongue blade.
  3. Swab the tonsillar areas from side to side; include any inflamed or purulent sites. Don’t touch the tongue, cheeks, or teeth with the swab.
  4. Immediately place the swab in the culture tube. If a commercial sterile collection and transport system is used, crush the ampule and force the swab into the medium to keep it moist.
  5. Note recent antimicrobial therapy on the laboratory request.
  6. Label the specimen with the patient’s name, physicians name, date and time of collection, and origin of the specimen. Also indicate the suspected organism, especially Corynebacterium diptheriae (requires two swabs and a special growth medium) and N. meningitides (requires enriched selective media).
Nursing Interventions
  1. Send the specimen to the laboratory immediately. Unless a commercial sterile collection and transport system is used, keep the container upright during transport.
Interpretation
Normal Results
  • Non-hemolytic and alpha-hemolytic
  • Neisseria species
  • Staphyloccoci
  • Diphtheroids
  • Some hemophilus species
  • Pneumococci
  • Yeats
  • Enteric gram-negative rods
  • Spirochetes
  • Veillonella species
  • Micrococcus species
Abnormal Results
  • Group A beta-hemolytic streptococci (Streptococcus pyogenes) (scarlt fever and pharyngitis).
  • Candida albicans (thrush)
  • Corynebacterium diphtheriae (diphtheria)
  • Bordetella pertusis (whooping cough)
  • N. gonorrhoeae
  • Neisseria meningitides
  • Mycoplasma and Chlamydia
Interfering Factors
  • Failure to report recent or current antimicrobial therapy on the laboratory request (possible false negative).
  • More than a 15 minute delay in sending the specimen to the laboratory.
Precautions
  • Obtain the throat specimen before beginning antimicrobial therapy.
  • Wear gloves when performing the procedure and handling of specimens.
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