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 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 center in Boston between the years of 1997-2015. 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 bacterialecause 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.