[DISTRIBUTION AND DRUG SENSITIVITY OF PATHOGENS IN PATIENTS WITH PROSTHETIC JOINT INFECTION AFTER PRIMARY TOTAL KNEE ARTHROPLASTY].

Objective: To provide the evidence for diagnosis and treatment of the complication by describing the distribution and drug sensitivity of pathogens in patients with prosthetic joint infection (PJI) after primary total knee arthroplasty (TKA).

Methods: Between January 2003 and June 2013, 65 cases (65 knees) with PJI after primary TKA were treated. There were 28 males and 37 females with an average age of 63.2 years (range, 37-80 years). The median interval between PJI and primary TKA was 2.8 years (range, 2 weeks to 11 years), including 29 left knees and 36 right knees. Prosthesis loosening could be found in 27 cases by X-ray examination. The average value of C-reactive protein and erythrocyte sedimentation rate was 37.4 mg/L (range, 12.5-197.0 mg/L) and 63.2 mm/1 h (range, 29.3-73.8 mm/l h) respectively. Preoperative and intraoperative synovial fluid as well as intraoperative tissue samples should be submitted for aerobic and anaerobic culture. The four types of infections were made according to the Tsukayama et al. classification standards.

Results: The patients were all diagnosed as having PJI. There were 5 (7.69%) type I infections, 4 (6.15%) type IIA, 8 (12.31%) type IIB, 3 (4.62%) type III, and 45 (69.23%) type IV according to the Tsukayama et al. classification standard. Bacterial culture results were negative in 12 cases and positive in 53 cases, the main pathogen was Gram-positive cocci (39/53). The most common organism identified was Coagulase-negative Staphylococcus (24/53) followed by Staphylococcus Aureus (12/53). Resistant bacterium accounted for 61.11% (22/36) of Staphylococcus. These bacterium were all sensitive to vancomycin, linezolid, meropenem, and fluconazole; and highly resistant to erythrocin, penicillin, and cefoxitin. The main pathogenic bacteria of Coagulase-negative Staphylococcus and Staphylococcus aureus had highest resistant rate to penicillin.

Conclusion: Gram-positive cocci is the main pathogen in patients with PJI after primary TKA, which is highly resistant to penicillin and macrolides. Antibiotic treatment of this complication should be based on the result of drug sensitivity test, vancomycin and linezolid may be used before the result of drug sensitivity test. It is important to pay attention to rare and multiple resistant bacteria.