Culture for isolation of group A Streptococcus only. CPT coding for microbiology and virology procedures often cannot be determined before the culture is performed. Routine susceptibility testing is not performed on group A streptococci because penicillin continues to be the drug of choice. There has been no resistance reported and surveillance for resistance is not recommended. If the patient is penicillin allergic, susceptibility test may be requested in the clinical information field. It will be performed at an additional charge. Requests with only a written order and no test number indicated will be processed according to Default Testing for Routine Microbiology.