The optimal duration of antibiotic treatment against invasive group B streptococci in adults has not been established, but a minimum of 2 weeks of therapy should be considered. SRA accession numbers for these isolates are provided in Table S2 in the supplemental material. Two distinct genetic elements are responsible for erm TR -mediated erythromycin resistance in tetracycline-susceptible and Adult b group strep strains of Streptococcus pyogenes. View large Download slide. Although all episodes of GBS bacteremia should prompt a search for the focus of disease, patients who have recurrent episodes must be thoroughly evaluated for a deep site of infection, and the evaluation should routinely include echocardiography. In some cases, GBS endocarditis can cause Adult b group strep of a valve or major embolic complications that necessitate early valve replacement [ 2425 ].