Comparative Analysis of Methicillin-Susceptible Staphylococcus aureus and Streptococcal Native Joint Septic Arthritis: Clinical Characteristics and Outcomes

Background/Objectives: This study aimed to evaluate and compare the clinical characteristics and outcomes of patients with methicillin-susceptible Staphylococcus aureus (MSSA) and streptococcal native joint septic arthritis (NJSA). Methods: This retrospective multicenter study included adult patients with NJSA from three tertiary care hospitals between 2004 and 2023. Patients were categorized into three groups based on bacterial virulence and differences among streptococcal species: MSSA, non-viridans streptococci, and viridans streptococci. Results: A total of 213 NJSA cases were identified, comprising 164 MSSA, 35 non-viridans streptococcal, and 14 viridans streptococcal cases. Non-viridans streptococcal NJSA exhibited significantly more acute clinical features associated with systemic inflammation, including frequent fever, leukocytosis, thrombocytopenia, elevated C-reactive protein levels, higher total bilirubin levels, and acute kidney injury, compared to MSSA and viridans streptococcal NJSA. The clinical presentations were similar between the MSSA and viridans streptococcal groups. The non-viridans streptococcal group showed a higher incidence of concomitant bacteremia, but a lower proportion of positive joint culture results. Treatment approaches were consistent across the groups, except for a shorter duration of antibiotic therapy in the viridans group. Treatment failure rates were comparable: 9.8% for MSSA, 14.3% for non-viridans streptococci, and 21.4% for viridans streptococci. Conclusions: This study highlights the heterogeneous nature of streptococcal NJSA, with non-viridans streptococci presenting more aggressive clinical manifestations despite similar treatment responses across groups. These findings challenge conventional views on streptococci as a less virulent pathogen than MSSA and emphasize the need for diagnostic and management strategies tailored to the unique pathogenic traits of these bacteria.