The purpose of the research is to help understand why some children become carriers of strep and whether children who are carriers need to be treated with antibiotics.

The overall objective of this investigation is to understand the differences in Group A streptococci in children who are acutely infected from those who are carriers. The hypothesis is that when in the carrier state, GAS exhibits unique transcriptional profiles that differ from those of the acute infection state. The investigators expect transcriptional profiles of GAS to provide important information regarding the changes the organism undergoes when transitioning between acute infection and carriage.

The specific aims of this study are:

1. To collect longitudinal participant-samples from acute and carriage phases of GAS infection and compare transcriptomic profiles and whole genome sequences of GAS recovered from acute and carrier pharyngeal swabs obtained from the same participants.
2. To evaluate how identified differentially expressed genes, or observed genetic polymorphisms, influence GAS models of bacterial colonization and pathogenesis.

To do this, the investigators will to identify 12 children with acute pharyngitis due to Group A streptococcus (GAS) who are pharyngeal carriers of GAS. Thirty percent of children 4 to 16 years of age with acute pharyngitis occurring between October and May will have a positive culture or rapid antigen detection test for GAS. Approximately 8-10% of these children with pharyngitis and a positive culture or rapid antigen detection test (RADT) for GAS will be carriers. Therefore,180 participants will need to be enrolled.

Inclusion Criteria:

• Children ages 5-15 years
• Positive rapid antigen detection test for group A streptococcus
• Parent or legal guardian present and able to provide consent
• Provider prescribes treatment with a beta lactam antibiotic
• English speaking

Exclusion Criteria:

• Unable to take beta lactam antibiotics
• Other concurrent bacterial infection, i.e., pneumonia

Children will be eligible for this study if they are ages 5 to 15 years and have been diagnosed to have acute pharyngitis caused by GAS (with a positive rapid antigen detection test (RADT). Children will be excluded if they are unable to take beta lactam antibiotics. Children will be enrolled at UW Health sites in Madison, Wisconsin, including both pediatric ambulatory care clinics and urgent care clinics. The study team will offer participants the option to complete follow-up study visits in-clinic