Laboratory: Clinical Microbiology
Test Name:
THROAT SWAB (PHARYNGITIS), CULTURE, AEROBIC BACTERIA
Test Code: TS
Clinical Information:
Test Indications:
Diagnosis of bacterial pharyngitis.
Most cases of pharyngitis are caused by viruses. Streptococcus pyogenes (Group A Streptococcus) is the most common bacterial etiology and accounts for 30% of pharyngitis cases in children and for ca. 10% of cases in adults. Diagnosis of strep throat is important especially in children, since severe sequelae like acute glomerulonephritis, acute rheumatic fever, or peritonsillar abscess can occur. Antimicrobial therapy alleviates pharyngeal symptoms and prevents some of the sequelae.
Occasionally, pharyngitis can be caused by other bacteria including Neisseria gonorrhoeae, Corynebacterium diphtheriae, and Arcanobacterium haemolyticum, but the laboratory will set up culture for these organisms only on specific request by the physician.

Recommendations:
Throat cultures are contraindicated for patients with inflamed epiglottis.
When Neisseria gonorrhoeae, Corynebacterium diphtheriae (sore throat, lymphadenitis, greyish pseudomembrane in throat, lack of vaccination), or Arcanobacterium haemolyticum (recurrent tonsillitis, pharyngitis with a rash, or indication of treatment failure) is suspected, please indicate on requisition.
Throat swabs for Neisseria gonorrhoeae culture should be collected using charcoal-containing transport medium and transported to the laboratory as soon as possible.
Samples and requisitions must be labeled/completed in accordance with the Shared Health Specimen Acceptance Policy.
Accurate patient identification must be made prior to sample collection. Patient identification should be done in accordance with the site policy.

Patient Preparation Instructions:
Depress the tongue with a tongue depressor. Sample the posterior pharynx, tonsils and inflamed areas.
If diphtheria is suspected, collect throat swab from beneath the pseudomembrane (if membrane can be removed).
Collection Devices:
Preferred Device:
Alternate Device: Dry Swab in Sterile Container for antigen detections.
Specimen Required: Throat Swab (Adult and Pediatric)
Referral:

Ensure samples that are being sent to a referral laboratory are packaged in accordance with Transport of Dangerous Goods recommendations for diagnostic samples.
Requisition:
Reference Values:
No Beta Haemolytic Streptoocci Group A, C or G isolated.
A final negative report will be sent after 2 days.
Availability:
Daily
See Also:
More Information:
Specimen Handling:
Local:  ≤2 hrs, store at room temperature.
Courier/local storage: ≤48 hrs (<24 hrs optimal), store at 4°C
If Neisseria gonorrhoeae is suspected, the swab should be placed in charcoal containing transport medium and be transported to the laboratory as soon as possible (≤12h).

References:
1.  Manual of Clinical Microbiology, 11th Edition, 2015. Versalovic et al., American Society for Microbiology, Washington, DC.
2.  A Guide to Specimen Management in Clinical Microbiology, 3rd edition, 2017. J. Michael Miller and Shelley A. Miller.  American Society for Microbiology, Washington, DC.
3.  Clinical Microbiology Procedure Handbook, 4th edition. 2016. Leber et al., American Society for Microbiology, Washington, DC.