Aerobic and anaerobic bacteria in deep infections after total hip arthroplasty: differential diagnosis between infectious and non-infectious loosening.

Five separate biopsy samples for bacterial culture were taken at primary total hip arthroplasty in patients without signs of infection and at reoperation of patients with infectious and noninfectious loosening of the prosthesis. Based on the results of the culture, on serologic results and on the erythrocyte sedimentation rate, bacteria of clinical significance could be distinguished from contaminants. Growth in one or two of five biopsy samples was a strong indicator of contamination, while growth in five of five biopsy samples of one or two bacterial species strongly indicated an infection. These diagnostic procedures are applied to differentiate between infectious and noninfectious loosening of the prosthesis. In the delayed infections, the low-virulent aerobic and anaerobic bacteria Staphylococcus epidermidis, Propionibacterium acnes and peptococci were predominant.