throat culture

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Throat Culture



A throat culture is a technique for identifying disease bacteria in material taken from the throat. Most throat cultures are done to rule out infections caused by beta-hemolytic streptococci, which cause strep throat. Hemolytic means that these streptococci destroy red blood cells.


The primary purpose of a throat culture is identification of the specific organisms that cause strep throat. These organisms are Group A streptococci, specifically Streptococcus pyogenes. Since most sore throats are caused by viral infections rather than by S. pyogenes, a correct diagnosis is important to prevent unnecessary use of antibiotics and to begin treatment of strep infections as soon as possible. Group A streptococcal infections are potentially life-threatening, often involving other parts of the body in addition to the throat. Besides causing sore throat (pharyngitis), streptococci can also cause scarlet fever, rheumatic fever, kidney disease, or abscesses around the tonsils.
Throat cultures can also be used to identify other disease organisms that are present in the patient's throat; and to identify people who are carriers of the organisms that cause meningitis and whooping cough.
Besides their use in diagnosis, throat cultures are sometimes used to test antibiotics for their effectiveness in treating different infections.


Throat cultures should be taken before the patient is given any antibiotic medications. In addition, the patient's immunization history should be checked to evaluate the possibility that diseases other than strep are causing the sore throat. The care provider should wash the hands carefully after taking the specimen to prevent the spread of any infectious organisms.


A throat culture test should be done on anyone who has symptoms of a strep throat. These symptoms include a sore throat that may be accompanied by a fever, body aches, and loss of appetite. Age is a consideration, in that strep throat is more common in children than in adults. The tonsils and the back of the throat often appear red, swollen, and streaked with pus. These symptoms usually appear one to three days after being exposed to group A strep. Because strep is highly contagious, family members and close contacts of patients diagnosed with strep throat should also have throat cultures performed if they show signs of the disease.
The specimen for throat culture is obtained by wiping the patient's throat with a cotton swab. The patient is asked to tilt the head back and open the mouth wide. With the tongue depressed and the patient saying "ah," the care provider wipes the back of the throat and the tonsils with a sterile swab. The swab is applied to any area that appears either very red or discharging pus. The swab is removed gently without touching the teeth, gums, or tongue. It is then placed in a sterile tube for immediate delivery to a laboratory. Obtaining the specimen takes less than 30 seconds. Laboratory results are usually available in two to three days. The swabbing procedure may cause gagging but is not painful. The doctor makes a note for the laboratory to indicate if any disease organisms other than strep are suspected, because some require special growth conditions in the laboratory.
S. pyogenes is cultured on a growth medium called blood agar. Agar is a gel that is made from the cell walls of red algae. Blood agar is made from agar gel and sheep's blood. When the throat swab reaches the laboratory, it is wiped across a blood agar plate. The plate is allowed to incubate for 24-48 hours to allow the growth of bacteria. If the organism is a Group A hemolytic streptococcus, the area immediately around the bacterial colony will be cleared of red blood cells. Hemolytic streptococci dissolve (lyse) red blood cells, leaving a clear zone surrounding the colony.

Alternative procedures

So-called instant strep tests are now available to help diagnose strep throat. They can be used in the doctor's office and take about 10-30 minutes to perform. Instant tests detect an antigen associated with the streptococcus. These tests are relatively new and not available at all clinics. Their reliability has improved since they were first introduced. If an instant throat test is negative, however, a standard throat culture can be performed to verify the results.


The patient does not need to avoid food or fluids before the test. Recent gargling or treatment with antibiotics, however, will affect the culture results. The laboratory should be notified if the patient has been recently taking antibiotic medications.


No specific aftercare is needed.


There is a minor risk for the health professional of exposure to the patient's illness.

Normal results

Normal results would include finding organisms that grow in healthy throat tissues. These organisms include non-hemolytic and alpha-hemolytic streptococci, some Neisseria species, staphylococci, diphtheria and hemophilus organisms, pneumococci, yeasts, and Gram-negative rods.

Abnormal results

In addition to S. pyogenes, other disease agents may be identified in the throat culture. Infectious agents that can be identified include Candida albicans, which can cause thrush; Corynebacterium diphtheriae, which can cause diphtheria; and Bordetella pertussis, which can cause whooping cough. In addition, the appearance of a normal organism in very high numbers may also be regarded as an abnormal result.



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Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311.

Key terms

Agar — A gel made from red algae that is used to culture certain disease agents in the laboratory.
Antibiotic — A drug given to stop the growth of bacteria. Antibiotics are ineffective against viruses.
Antigen — A substance that interacts with an antibody and causes an immune reaction.
Carrier — A person harboring an infectious disease who may be immune to it but who can give it to others.
Diphtheria — A serious disease caused by a bacterium, Corynebacterium diphtheriae.
Hemolytic — Able to dissolve red blood cells. The bacteria that cause strep throat are hemolytic organisms.
Streptococcus — A category (genus) of sphere-shaped bacteria that occur in pairs or chains.
Thrush — A disease occurring in the mouth or throat that is caused by a yeast, Candida albicans.
Whooping cough — An infectious disease of the respiratory tract caused by a bacterium, Bordetella pertussis.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

throat culture

The placing of a sample swabbed from the throat–posterior pharynx, tonsils and tonsillar fossa, and any area grossly suggestive of inflammation in the appropriate culture medium to detect the growth of a pathogen of interest–eg, group A streptococci
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
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GGS was identified in a throat culture, and serial change in ASOT level suggests she was infected with GGS before exacerbation of her involuntary movements, which were probably caused by a postinfectious immune-mediated process.
Vigilance for GAS infection in family members is appropriate, including obtaining throat cultures from persons with pharyngitis and treating them promptly when results are positive.
Performance of a rapid antigen-detection test and throat culture in community pediatric offices: implications for management of pharyngitis.
Because patient A specifically sought health care and a throat culture as a result of patient B's death, determining whether the S.
If your child has a rash and the doctor suspects scarlet fever, he or she will usually take a throat culture (a painless swab of throat secretions) to see if the bacteria grow in the laboratory.
Patients can go from diagnosis to treatment without a doctor's visit and without waiting for the results of a traditional throat culture, which can take 24 to 48 hours.
[4] The seven categories were thus: (i) empirical treatment with IM penicillin (Treat All); (ii) treatment based on a positive throat culture (Culture All); (iii) treatment based on a symptomatic score of 2 using a modified WHO CDR (CDR 2+); (iv) treatment based on a CDR score of [greater than or equal to] 3 (CDR 3+); (v) treating those with a CDR score of [greater than or equal to]2, culturing those with CDR scores <2 and then treating positive cultures (CDR2+, Culture CDR negatives); (vi) treating those with a CDR [greater than or equal to] 3, culturing those with CDR scores <3 and treating positive cultures (CDR3+, Culture CDR negatives); and (vii) observation only (Treat None).
Throat Culture: In this test the doctor rubs a cotton swab against the back of patient's throat.
Diagnosis should be made by throat swab and testing by rapid antigen detection test (RADT) and/or throat culture. Both tonsils, or tonsillar fossac, and posterior pharynx should be swabbed to provide an accurate and adequate sample.
Acute guttate psoriasis is strongly associated with preceding and concurrent streptococcal infection particularly of the throat.3 In one study streptococci were isolated from the throat of 97 Percent patients with guttate psoriasis.4 Although streptococcal throat infection can clearly trigger the guttate psoriasis only 20-30 Percent throat culture cases were positive in chronic plaque type
Throat culture was taken and 1 gr of sulbactam-ampicillin three times per day and 2.5 mg of metamizole sodium four times per day were administered.
We conducted a study to define the sensitivity and specificity of RADT, using throat culture results as the gold standard, in 100 emergency department patients who presented with symptoms consistent with streptococcal pharyngitis.