Nongonococcal infectious arthritis is an acute or subacute illness with potentially significant morbidity and mortality. It can be caused by bacteria, mycobacteria, or fungi. Both healthy individuals and individuals with predisposing conditions can be infected. Nongonococcal infectious arthritis is typically a monoarticular disease, but in approximately 10% of patients, it affects multiple joints. [1, 2] Without treatment, the condition results in joint destruction.
Pathophysiology and Etiology
Infectious arthritis ensues when foreign organisms invade the synovium or joint space. These organisms invade the joint via the following 3 pathways:
Hematogenous dissemination from a distant site
Periarticular infection, such as osteomyelitis or adjacent soft-tissue infection
Direct introduction through penetrating trauma or procedural intervention, such as arthrocentesis or surgical repair
Gram-positive cocci, especially Staphylococcus aureus, are the predominant etiologic agents. Streptococcal species are also common, especially group A streptococci.  If a prosthetic joint was implanted within the preceding 6 months, S epidermidis and S aureus are major pathogens.
Gram-negative bacilli are more common in elderly patients with chronic medical conditions. Pseudomonas aeruginosa and methicillin-resistant S aureus (MRSA) are more prevalent in the infectious arthritis that affects individuals who abuse intravenous (IV) drugs. Salmonella species exhibit a predilection for individuals with systemic lupus erythematosus.
Dubost and colleagues examined changes in the distribution and antibiotic susceptibility profiles of organisms responsible for septic arthritis in a single-center retrospective study of 374 patients treated between 1979 and 2008 at a French hospital. Over the three decades studied, no significant time trends in the proportions of staphylococci (67%, 65%, and 64%), streptococci (14%, 21%, and 17%), or Gram-negative rods (7%, 10%, and 14%) were detected. Tuberculosis was significantly more common between 1979 and 1988 (10%, 4%, and 2% over the three decades studied). There were no significant changes in the proportions of methicillin-resistant staphylococci over time (13%, 11%, 15%). 
In addition to the common pathogen Mycobacterium tuberculosis, nontuberculous species, such as Mycobacterium kansasii, may spread from a pulmonary focus and infect a joint. Mycobacterium marinum should be considered in individuals exposed to aquatic or marine environments.
Candida organisms, including Candida albicans and Candida parapsilosis, may cause infectious arthritis in debilitated hospitalized patients or in patients on long-term antibacterial therapy. Sporothrix schenckii may infect the hand or wrist joints of a person frequently exposed to moist soil, rose thorns, or the outdoors.
The presence of a preexisting, chronic, inflammatory, destructive arthritis, especially rheumatoid arthritis, is correlated with infectious arthritis. The introduction of anti–tumor necrosis factor (TNF) agents into the treatment of inflammatory arthritis may further predispose this population to infectious arthritis.
A person undergoing immunosuppressive therapy, such as with corticosteroids or cytotoxic agents, is more likely to become infected. A person who has a prosthetic joint has greater risk of infection. Elderly individuals are at particular risk for infectious arthritis. Comorbid nonarticular conditions, such as diabetes mellitus, immunodeficiency diseases, cancer, or IV drug abuse, also increase the risk of infectious arthritis.
Epidemiology and Prognosis
Age older than 80 years has been shown in some studies to be an independent risk factor for susceptibility to bacterial arthritis. Sex is not an independent risk factor for infectious arthritis. No inherent racial predilections for infectious arthritis are recognized.
Nongonococcal infectious arthritis carries a mortality of 11%.  Irreversible loss of joint function may result if the condition is not treated immediately and for an appropriate duration. Joint destruction occurs in 25%-50% of cases.  Morbidity and mortality are higher in elderly individuals and individuals with preexisting medical conditions.
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