Sodium Aurothiomalate, Gold Keratinate, and Various Tetracyclines in Mycoplasma-Induced Arthritis of Rodents

Sodium aurothiomalate (ATM), gold keratinate and five different tetracyclines were investigated for activity against M. arthritidis strain ATCC 14124 and M. pulmonis strain JB, both in vitro and in rodents with arthritis caused by these mycoplasmas. In vitro, ATM had only slight activity against M. arthritidis and M. pulmonis, while gold keratinate was virtually inactive against M. pulmonis. In contrast, the tetracyclines were highly active against both mycoplasmas. The tetracyclines and the gold salts were both predominantly mycoplasmastatic. In both rats and mice, parenteral administration of ATM, begun shortly before or after infection of rodents with mycoplasmas, prevented the development of arthritis. ATM or gold keratinate, given subcutaneously to mice already arthritic from infection with M. pulmonis, reduced the severity of the arthritis, even although gold keratinate was inactive aganist this mycoplasma in vitro. Moreover, direct testing of serum, collected from mice treated with gold keratinate, failed to demonstrate antimycoplasmal activity in vitro. These results suggest that the action of gold-containing drugs in mycoplasmal arthritis is due to biological properties of gold other than antimycoplasmal activity. Tetracyclines were also found to be effective in preventing arthritis in rats and mice when given subcutaneously. With high doses, subcutaneous, but not oral, therapy significantly reduced the severity of established arthritis in mice infected with M. pulmonis. The blood levels achieved with the different tetracyclines, when related to their therapeutic activity, indicated that good antimycoplasmal activity and adequate absorption from the gut were not the only properties needed for optimal effectiveness. The results are discussed in relation to treatment of rheumatoid patients with tetracycline HCl.