Septic arthritis due to dual infection with Mycoplasma hominis and Ureaplasma urealyticum.

: Acute septic arthritis of a knee and shoulder developed in a 32-year-old renal transplant patient. Cultures yielded Mycoplasma hominis and at least 1, and possibly 2, strains of Ureaplasma urealyticum. Doxycycline therapy controlled the symptoms and signs, and the joints became culture negative. On stopping therapy after 7 months, the arthritis recurred and U. urealyticum was again isolated from the shoulder joint. Cessation of doxycycline almost 4 years after the initial episode resulted in another recurrence. To our knowledge, this is the 1st case in which both M. hominis and U. urealyticum have been isolated from a joint.