[Two cases of septic arthritis by Mycoplasma hominis after total knee replacement arthroplasty].

Mycoplasma hominis has been related with pelvic inflammatory illnesses and postpartum and neonatal infections. Extragenital M. hominis infections are rare, but septicemia, septic arthritis, wound infection, meningitis, and other infections in Immunocompromised patients have also been described. Here we report two cases of septic arthritis caused by M. hominis in patients following total knee replacement arthroplasty. After the surgery, the patients presented with knee pain and clinical signs of infection, such as fever, erythema and swelling on the surgical site. Arthroscopic debridement operations were performed on the surgical site. M. hominis was isolated from the joint fluid and identified by the microscopic visualization of the typical "fried-egg-type" colonies on Mycoplasma specific agar (pleuropneumonia-like organism agar). It was also confirmed by 16S rRNA sequencing. To the best of our knowledge, this is the first report of prosthetic joint infections with M. hominis in Korea.