Meaning of throat swab test

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Article written by a doctor of Laboratory - Vinmec Central Park International General Hospital

The throat swab test method helps to directly and quickly detect group A beta-hemolytic streptococci in throat swab samples.

1. What symptoms should the patient have to do a throat swab test?

Throat swab is prescribed by the doctor before patients need to determine whether or not they have a bacterial oropharyngeal infection. Symptoms of the patient: sore throat, burning in the oropharynx, painful swallowing... Examination found: Red throat, mucous membranes of the oropharynx swelling, redness, edema, possibly pus, purulent tonsillitis or pseudomembranous edema, edema Urinary tract, strawberry red tongue, swollen neck lymph nodes. Diagnosis of pharyngitis, tonsillitis. Detecting healthy people carrying bacteria: S. aureus, N. meningitidis, S. pyogenes (Group A), C. diphtheriae.

2. How is throat swab test done?

Specimen: swab the throat, take samples in the area with inflammation, tonsils to avoid touching the tongue, palate, cheek mucosa. Sampling before antibiotic administration, as soon as the diagnosis is made. Transport: Send immediately to the laboratory or discard in Amies/Stuart transport medium (with cultures). Direct investigation: Gram stain: Gram stain only when the doctor asks to find bacteria in the form of diphtheria, spirochetes, and yeasts. Do not stain Gram to look for the shape of other bacteria such as streptococcus, staphylococcus in the throat fluid has no value because in the swab of the throat of non-diseased people (normal people) can also be seen. Alkaline methylene blue stain when ordered by your doctor to look for diphtheria bacteria. Culture:
Target is group A streptococcus : Throat swab is inoculated on a box of sheep blood agar (Blood Agar) and placed in the area with the most inoculum (first inoculation area 1) a plate of Bacitracin and a plate of Co. Trimoxazole (Bactrim). Incubate box BA in an incubator of 35 degrees C - 37 degrees C with 5% CO2 for 18 -48 hours. Then are identified and perform antibiogram. Follow the following scheme:

Find N. gonorrhoeae (gonococcal pharyngitis): Culture on agar Incubate CATM box (Thayer Martin brown agar), incubator at 35 degrees C - 37 degrees C with 5% CO2 for 18 - 48 hours. Culture for diphtheria: inoculate loeffler agar incubate at 35-370C for 6-8 hours, then re-inoculate on BA blood agar with tellurite for selection or can be cultured on BA with tellurite from the beginning. Immunological methods:
Purpose of finding specific antigens for group A beta-hemolytic streptococci There are many methods such as ELISA, immunochromatography, latex coagulation. Immunochromatographic or latex agglutination methods are most appropriate to perform at the clinic. Has high sensitivity and specificity, is easily performed in the clinic. PRINCIPLES OF TESTING:

3. Meaning of throat swab test

Immunohistochemical test method (Latex immunochromatography) directly and rapidly detects group A beta hemolytic streptococci in throat swab samples:
This is an immunohistochemical test for detecting Carbohydrate antigens C of group A beta-hemolytic streptococci in the oropharynx. The tests have a very high sensitivity and specificity, comparable to cultures, very easily done in the office or clinic, and the results are also very fast in just 10 minutes. Therefore, this is a test that should be available at the clinic because pharyngitis is a very common condition and the requirement to find group A streptococcus is also a very necessary requirement to help differentiate from inflammatory agents. throat, also helps doctors to treat correctly in the first place. Culture: The most common bacteria in pharyngitis is Group A hemolytic Streptococcus:
Find group A streptococcus: report the exact species of the organism as the identified target bacteria with the results of the Antibiogram Group Streptococcus A. Identify group A: if sensitive to Bacitracin, Anti-Co-Trimoxazol or can identify and antibiogram by automatic machine or agglutinate Group A.

If the isolates are N. meningitidis, Staphylococci (S. aureus, S. epidermidis), S. pneumoniae, Haemophilus spp., Yeast (Candida spp.). These bacteria are all resident bacteria in the oropharynx. Results are returned only when requested by a doctor to find healthy carriers of the infection or when the number of bacteria is in the majority and when a doctor explicitly requests to find these bacteria. Mushroom culture: return identification results and antibiogram if the number predominates or the doctor requires. Find N. gonorrhoeae (gonococcal pharyngitis): return identification results and antibiogram. Diphtheria culture: after incubation for 24-8 hours, if bacteria grow, Gram stain, if diphtheria bacteria shape, identify and test for toxin to identify pathogenic diphtheria bacteria.