Spondylodiscitis caused by viridans streptococci: three cases and a review of the literature

Three cases of spondylodiscitis caused by viridans streptococci were observed within the course of 1 month. Although streptococci have been reported as the third most frequent cause of spondylodiscitis after staphylococci and gram-negative bacteria, alpha-haemolytic streptococci are rarely seen. The three patients presented with symptoms of low back pain; they felt well and did not have a fever or chills. Laboratory examinations revealed inflammation. Further examinations such as scintigraphy, computed tomography or magnetic resonance imaging were done. Bacteriological diagnosis was established by blood cultures in two cases and by needle biopsy of the disco-vertebral space in one. In one patient endocarditis was also documented. Because the prevalence of endocarditis was found to be higher in our cases of spondylodiscitis due to Streptococcus viridans than for other bacteria, the exclusion of this diagnosis must be pursued aggressively. These observations lead us to question if the spectrum of bacteria causing spondylodiscitis is undergoing a change. an aetiological agent could be isolated in 1168 patients (85.4%): in 48% a staphylococcus, in 28% a gram-negative bacterium and in only 10% a streptococcus. There were two cases of viridans streptococci (0.2%). These two cases together with other single case reports [14-22] account for 15 cases of spondylodiscitis due to alpha-haemolytic streptococci. Differentiation of the organisms to the species level was accomplished in six cases: S. mitis (3), S. sanguis (2) and S. anginosus (1). Although a multitude of organisms, bacterial as well as fungal, causing spondylodiscitis has been reported in recent years, almost all were single cases [23-42]. The unusual observation of three cases of spondylodiscitis due to alpha-haemolytic streptococci within 1 month prompted us to review the clinical and laboratory findings and to compare these cases with those caused by Staphylococcus aureus.