Septic arthritis: patients with or without isolated infectious agents have similar characteristics

Purpose Septic arthritis can be disabling and life-threatening, requiring prompt diagnosis and treatment. The infectious agent is not always identified in these patients. We revaluate septic arthritis cases discharged from our department, describing the affected population, causative microorganisms and antibiotic therapy used, and characterised differences between patients with and without isolated pathogenic agents. Methods Sixty-eight septic arthritis patients were included in this study. Diagnosis was based on clinical findings, and/or the presence of joint purulent material, and/or bacterial pathogen isolation from joint fluid/synovial membrane/blood cultures and response to antibiotics. Data analysis was performed using SPSS 20. Results Patients had a mean age of 61.1 +/- 18.8 years, without sex predominance. 26.5 % had an infection <= 15 days before septic arthritis diagnosis. Besides previous infection, 57.4 % had >= 1 risk factors for septic arthritis, most commonly pharmacological immunosuppression (20.6 %), diabetes mellitus type 2 (19.1 %) and rheumatoid arthritis (17.6 %). The knee was the most often affected (54.3 %). Only 39.7 % presented fever from clinical onset until hospital admission (mean 13.4 +/- 18.9 days). Leucocytosis was present in 45.6 % of patients, elevated erythrocyte sedimentation rate (ESR) in 75 % and elevated C-reactive protein (CRP) in 97.1 %. 5.9 % had articular damage attributable to septic arthritis. An infectious agent was isolated in 41.2 % of patients, with Staphylococcus aureus being the most frequent. 38.7 % of synovial fluid and 23.5 % of synovial membrane cultures were positive. Patients with an identified infectious agent have no significant differences other than more days of hospitalisation (p = 0.003) and in-hospital antibiotic treatment (p = 0.017). Conclusion Synovial fluid and synovial membrane cultures more often identified pathogens compared to blood or urine cultures. Patients with and without an identified infectious agent have similar demographic, clinical, laboratory and radiographic characteristics.