Streptococcal septic arthritis in adults. A study of 55 cases with a literature review.

Objectives: To evaluate the rate of occurrence and characteristics of streptococcal septic arthritis.

Methods: Retrospective single-center study of patients with bacteriologically documented septic arthritis admitted to a rheumatology department over a 20-year period.

Results: Of 303 cases of septic arthritis, 55 (18%) were due to streptococci and 166 (55%) to Staphylococcus aureus (55%). As compared to patients with S. aureus arthritis, patients with streptococcal arthritis was more likely to be in female (56% vs. 36%, P < 0.006) and older than 60 years of age (71% vs. 58%), less likely to have comorbidities (36% vs. 56%), rheumatoid arthritis (5% vs. 19%, P < 0.01), or diabetes (2% vs. 15%, P < 0.01), and more likely to have cancer (13% vs. 7%). Involved joints and proportions of patients with arthritis in multiple joints were similar in two groups. Mortality was lower in the group with streptococcal infection (3.6% vs. 7.8%). The streptococci were distributed as follows: group A (n = 7), group B (n = 12), group C (n = 4), group D (n = 7), group F (n = 1), group G (n = 2), nongroupable (n = 14), nontypable (n = 1), and Streptococcus pneumoniae (n = 7). Groups A and B and nongroupable strains mainly affected women; group A selectively involved younger patients and group B very elderly patients. Comorbidity, most notably cancer, was common in patients with S. pneumoniae or group D streptococci. The portal of entry was often a skin lesion for groups A and B and a medical procedure for group D. Multiple joint involvement was common with groups A and B and prosthetic joint infection with groups B and C. Group A and S. pneumoniae were associated with severe systemic symptoms and extra articular foci of infection, whereas a smoldering course was more common with groups D and G and with nongroupable strains. Residual joint abnormalities were noted in half the patients, with no differences across groups.

Conclusions: The features of streptococcal septic arthritis vary according to the group of the causative organism and differ from those of S. aureus arthritis.