The proportion of invasive Streptococcus pneumoniae isolates that are drug resistant has reached an alarming level. Circumstantial evidence suggests that antibiotic prescribing patterns are at least in part responsible. The currently available polysaccharide pneumococcal vaccine could prevent a substantial number of these infections in adults. Cirrhosis, diabetes, breast cancer, certain neurological conditions, and central venous catheters have been confirmed to be risk factors for group B Streptococcus infection. In one study, almost 5% of adults with invasive group B Streptococcus had recurrent infection. The incidence of and risk factors for invasive group A Streptococcus infection have been further defined.