Final answer:
Staphylococcus aureus is the most common cause of both septic arthritis and osteomyelitis. Diagnosis includes synovial fluid analysis, and treatment is with antimicrobial drugs appropriate to the identified pathogen.
Step-by-step explanation:
The most common cause of both septic arthritis and osteomyelitis is Staphylococcus aureus. This bacterium is particularly adept at invading joint spaces and bones, leading to these conditions. A diagnosis of infectious arthritis includes aspirating synovial fluid for evaluation, including culture, antimicrobial susceptibility testing, and sometimes PCR analysis. Treatment typically involves the administration of antimicrobial drugs based on susceptibility testing. For staphylococcal infections, β-lactams like oxacillin and cefazolin are often used.
In the case of β-lactam-resistant Neisseria infections, third-generation cephalosporins such as ceftriaxone are indicated. For mycobacterial or fungal infections, longer-term antimicrobial therapy is employed. Even with treatment, there are significant risks of permanent joint damage and mortality associated with infectious arthritis. Treatment typically includes the administration of appropriate antimicrobial drugs based on antimicrobial susceptibility testing. Mortality rates range from 5% to 20% and permanent joint damage can occur in about 40% of patients with nongonococcal infectious arthritis.