Infection of joints associated with fever and other systemic symptoms. Joint destruction occurs if the infection is not treated expeditiously. Removal of pus from the joint is necessary. In older or immunosuppressed patients, the most common causative organism is Staphylococcus aureus. Staphylococci, anaerobes, or gram-negative bacteria are found in prosthetic joint infections. Gonococci and Borrelia burgdorferi, the spirochete that causes Lyme disease, differ from other forms of bacteria that cause joint infection in that they tend to affect younger and more active individuals.