UNLABELLED The pathogenic capacity of streptococcus agalactiae or Group B Streptococcus (GBS) has been increasing in nonpregnant adults. We carried out a study about the pathogenic capacity and susceptibility to antibiotics of GBS strains isolated between January 2003 and June 2004 in Farhat Hached hospital of Sousse (Tunisian general hospital). METHODS Identification of strains was carried out according to usual bacteriological characters. Susceptibility of GBS to antibiotics was carried out according to CA-SFM recommendations. RESULTS during the study period, sixty strains were isolated. They were essentially isolated from the urinary tract (52%) and the skin (36.2%). Women accounted for 68 percent of the cases. Among the 30 hospitalized patients, 20 (66%) had serious underlying disease. Diabetes mellitus was predominant (80%). All group B streptococci isolates were susceptible to amoxicillin, penicillin G, vancomycin and to pristinamycin. Sixty four percent of isolates were susceptible to erythromycin. Among the invasive infection, caused by GBS in nonpregnant adults, skin and urinary tract infections were the most common. All isolates were susceptible to amoxicillin, penicillin G. vancomycin and to pristinamycin.