Septic arthritis

Background

Microbiology

• Gonococcal: Neisseria gonorrhoeae, more common in young, sexually active adults
• Non-gonococcal bacterial:
  • Staphylococcus aureus, in immunocompetent and immunocompromised people as well as those at risk for Staphylococcus aureus bacteremia; this is the most common causative organism overall
  • Group B streptococci, more common in poorly-controlled diabetes
  • Streptococcus pneumoniae, more common in patients with hyposplenia
  • Enterobacteriaceae, especially if GI illness, or immunocompromised patients and those who inject drugs
  • Pseudomonas, more common in diabetes, immunocompromised, trauma, or water exposures
  • Aeromonas, more common after exposure to brackish water
  • Salmonella, especially in patients with sickle cell disease or HIV
  • Eikenella corrodens and Peptostreptococcus, especially if recent bite or other oral flora contamination
  • Pasteurella multocida, after cat bite
  • Capnocytophaga, after dog bite
  • Mycoplasma hominis, with postpartum septic arthritis, recent genitourinary tract manipulation, and immunocompromise
• Other:
  • Mycobacterium tuberculosis and non-tuberculous mycobacteria (especially Mycobacterium chelonae and Mycobacterium fortuitum
  • Fungal infections including Candida, Blastomyces dermatitidis, Cryptococcus, Coccidioides immitis, and Sporothrix schenckii
  • Viral infections including HIV, hepatitis B virus, hepatitis C virus, parvovirus B19, and alphaviruses including chikungunya virus

Investigations

• Note: for fluid analysis, 1 cells/microL = 1,000,000 (1E6) cells/L; alternatively 1E9 cells/L = 1,000 cells/microL

Management

• Empiric: typically treated empirically with vancomycin and ceftriaxone empirically, followed by directed therapy

Gonococcal Arthritis

• Ceftriaxone 1 g IV daily for 7 to 14 days
• Don't forget azithromycin 1 g po once

Non-Gonococcal Arthritis

• Treated with targetted antimicrobials
• Duration is traditionally 4 weeks, including at least 2 weeks of parenteral antimicrobials
• However, can do as short as 2 weeks for hand and wrist septic arthritis