Bacteriology of viridans streptococcal bacteremia

In order to assess the species distribution and the antibiotic susceptibility of viridans streptococci in various human infections, we reviewed 164 cases of viridans streptococcal bacteremia seen at the National Taiwan University Hospital between May 1981 and April 1987. The organisms were isolated from 83 patients with endocarditis. Among 81 nonendocarditis patients, only 54 had clinically recognizable foci of suppurative inflammation. Mainly based on API 20 STREP system of species identification, S. sanguis II accounted for 24.4%; S. mitis, 20.7%; S. sanguis I, 20.1%; and S. milleri 2, 11.6% of the 164 cases studied. Of 83 endocarditis patients, 27.7% were S. sanguis I; 21.7%, S. sanguis II; and 16.9%, S. mitis. In nonendocarditis bacteremia with known suppurative lesions, 3 most often isolated organisms were S. sanguis II (24.0%), S. mitis (24.0%), and S. milleri 2 (24.0%). In nonendocarditis bacteremia without suppurative infection, the most frequent isolates were S. sanguis II (33.3%) and S. mitis (25.9%). In terms of relative frequency between endocarditis and nonendocarditis cases, S. mutan, S. sanguis I, and S. bovis had the highest frequency ratio of 7:1, 3.5:1, and 1.5:1, respectively. All isolates were susceptible to penicillin G, ampicillin, and cephalothin. Tetracycline resistance, however, were observed in 35.4% of the isolates; oxacillin resistance, 11.0%; and erythromycin resistance, 9.1%.