Streptococcal vertebral osteomyelitis: multiple faces of the same disease.

The role of Streptococcus species as an aetiological microorganism of vertebral osteomyelitis (VO) is considered to be of little relevance. We aimed to describe a large number of cases of streptococcal vertebral osteomyelitis (SVO), to analyze the clinical features associated with different Streptococcus species, and to compare them with a cohort of patients with VO caused by Staphylococcus aureus. An incidence study and a retrospective, multicenter, observational clinical study of cases of SVO (1991-2011) were performed. Statistical comparison of SVO by different species and between them and staphylococcal VO was carried out. Over the whole period there was an increasing incidence in the number of VOs and SVOs per year (p <0.05). Among 58 cases of SVO, those caused by non-viridans streptococcus (Streptococcus pneumoniae, Streptococcus agalactiae and Streptococcus pyogenes; n = 26) mimicked VO by S. aureus, and presented with more fever, neurological symptoms and paravertebral abscesses in comparison with those caused by the viridans group (remaining species). In contrast, the latter have a sub-acute clinical picture and were associated with the presence of endocarditis (p <0.05). Among non-viridans SVOs, concomitant infection was specifically related to S. pneumoniae (p <0.05). In conclusion, SVO presents a wide range of clinical patterns. The relationship between VO and diagnosis of endocarditis was established with SVO caused by the viridans group. Whereas non-viridans SVO mimics acute characteristics of VO caused by S. aureus, cases of viridans SVO are significantly more likely to have a sub-acute clinical presentation. The increased incidence of SVO during the last decades could support a new epidemiological scenario.