IMMUNOPATHOLOGICAL FEATURES OF RAT STAPHYLOCOCCUS-AUREUS ARTHRITIS

Staphylococcus aureus is the most common bacterial species found in no ngonococcal bacterial arthritis in humans. We present the first descri ption, to our knowledge, of an outbreak of spontaneous staphylococcal arthritis in a rat colony. In a group of 10 rats, 9 displayed arthriti s. Clinically, the most obvious findings were arthritis of one or both hindpaws and malaise. Bacteriophage typing showed the common phage ty pe 85 in isolates recovered from the joints, blood, and bedding of rat s and from the nose and cheeks of one person from the staff of the ani mal facility. The S. aureus strain proved to produce staphylococcal en terotoxin A and exhibited strong binding to collagen types I and II an d bone sialoprotein, which are potentially important virulence factors . When the recovered S. aureus strain was injected intravenously into healthy mts, severe septic arthritis was induced in almost all of the animals. The arthritic lesions were characterized by infiltration of p hagocytic cells and T lymphocytes into the synovium. Many of the synov ial cells strongly expressed major histocompatibility complex class II molecules. Increased levels of interleukin 6 in serum as well as a pr ominent polyclonal B-cell activation were noted throughout the disease course. Pretreatment of S. aureus-injected rats in vivo with an antib ody to the alpha beta T-cell receptor significantly decreased the seve rity of the arthritis. Our results indicate that alpha beta(+) T lymph ocytes contribute to an erosive and persistent course of S. aureus art hritis.