Organism

Bacterial/septic arthritis

Infant (<3 months): S. aureus (GPC), Group A streptococci (GPC), Enterobacteriaceae (GNR), Kingella kingae (GNCB), Haemophilus influenzae (GNCB).

Child (3 months to 6 years): S. aureus (35%), H. influenzae, group A streptococcus (GPC) (10%), Enterobacteriaceae (6%), Borrelia burgdorferi (Lyme), S. pneumoniae (GPC), K. kingae .

Adult, STD not likely: S. aureus (40%), group A streptococcus (27%), Enterobacteriaceae (23%), Streptobacillus moniliformis (GNR) (rat bite fever), brucella (GVCB) ( Neisseria sp.), Mycobacterium marinum (AFB).

Adult, STD likely: N. gonorrhoeae (GNDC) (disseminated gonococcal infection [DGI]).

Prosthetic joint, postoperative or following intra-articular injection: Coagulase-negative staphylococci (40%), S. aureus (20%), viridans streptococci (GPC in chains), enterococci (GPC), peptostreptococcus (GPC), Propionibacterium acnes (GPR), Enterobacteriaceae, Pseudomonas sp.