Throat Culture

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Testing for treatment

Halos form to show effectiveness of different antibiotics

The most common bacterial cause of a sore throat is an infection with group A streptococcus. If these harmful bacteria have been identified in the throat culture, then the affected person will be treated with antibiotics. Because the appropriate antibiotic therapy is predictable for group A streptococcal infection, no further testing is usually necessary.

However, other types of cultures that are positive for pathogenic bacteria may require an antibiotic susceptibility test, which grows the bacteria in the presence of a panel of antibiotics to see which antibiotics may be effective for treating the infection. For one example of a susceptibility method, the bacteria are swabbed onto an agar plate and antibiotics that are impregnated into filter paper disks are placed on the plate. Following an overnight incubation step, the absence of bacterial growth around the disk indicates the ability of that antibiotic to inhibit the bacteria. The results of this test inform the doctor which antibiotic he or she can prescribe to cure the infection.

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