Microbiology of polymicrobial prosthetic joint infection.

Prosthetic joint infection (PJI) is a rare but challenging complication of arthroplasty. Herein, we describe the epidemiology and microbiology of PJI, with a focus on analyzing differences between the microbiology of polymicrobial versus monomicrobial infection of hip, knee, and shoulder prostheses. In addition, we report the most frequent co-pathogens in polymicrobial infections, as detected by culture. A total of 373 patients diagnosed with PJI at Mayo Clinic were studied. For hip and knee arthroplasties, a higher proportion of fractures (P = 0.02) and a shorter time between the implantation and symptom onset (P < 0.0001) were noted in polymicrobial versus monomicrobial PJI. The most common microorganism detected, Staphylococcus epidermidis, was more frequently detected in polymicrobial (60%) versus monomicrobial (35%) PJI (P = 0.0067). Among polymicrobial infections, no co-pathogens were more frequently found than others, except S. epidermidis and Enterococcus faecalis which were found together in 5 cases. In addition to coagulase-negative staphylococci and enterococci, Corynebacterium species and Finegoldia magna were common in polymicrobial infections. Conversely, there was no difference between the prevalence of Staphylococcus aureus, Gram-negative bacilli, or Cutibacterium acnes between the polymicrobial and monomicrobial groups. The microbiology of polymicrobial PJI is different from that of monomicrobial PJI.