The profile of the causative organisms which lead to septic arthritis of native joints over the last two decades in a single tertiary medical center in the east coast of the United States.

BACKGROUND: Septic arthritis (SA) is associated with significant morbidity and mortality. Delayed or inadequate treatment may result in joint destruction, osteomyelitis and sepsis. Like other types of infection, the causative agents of SA may have changed over time. Early targeted intervention is important in cases of SA and can be achieved only by understanding the current trends in the microbiology of SA. OBJECTIVES: To determine the trends in the microbiology of SA over the last two decades. METHODS: We conducted a retrospective study including all patients 18 and older with culture positive, surgically treated, native joint septic arthritis (NJSA), admitted to a single tertiary medical centre in Boston between the years of 1997 and 2015. We excluded cases of osteomyelitis and septic bursitis. We focused our analysis on the microbiology data which included synovial fluid gram stain and culture, blood cultures and synovial biopsy cultures. RESULTS: Among 260 cases, the most common bacteria isolated were Methicillin Sensitive Staphylococcus aureus (MSSA, 36%), Methicillin Resistant Staphylococcus aureus (MRSA, 17.6%), Coagulase Negative Staphylococci (CoNS, 13%) and Group B Streptococcus (GBS, 7.3%). Trends in the rates of these bacteria demonstrated no significant variation. The knee was the most common joint affected, followed by the shoulder and hip. Shoulder SA was most commonly caused by MRSA while MSSA was the leading causative organism in other joints. GBS was a causative bacterium in shoulder SA significantly more often than in knee or hip infections. CONCLUSIONS: Although no significant trends were noted in the microbiology of SA over nearly 2 decades, we observed meaningful findings regarding shoulder SA as MRSA was the most common bacterial because of SA in this joint. Prompt joint aspiration, microbiologic testing of synovial fluid and empiric antibiotic therapy that covers MRSA may improve outcomes in SA.