Extending the culture duration could not improve the culture positivity rate and clinical outcomes of periprosthetic joint infection

Baijian Wu^1,2Yuan Lin^2,3Jinhui Su²Lan Lin^1,2Zhenggui Yu²Chaofan Zhang^1,2Xinyu Fang^1,2Zida Huang^1,2Wenming Zhang^1,2*

• ¹Department of Orthopaedic Surgery, National Regional Medical Center, Binhai Campus of the First Affiliated Hospital, Fujian Medical University, Fuzhou, Fujian Province, China
• ²Department of Orthopedics, First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian Province, China
• ³Department of Orthopaedic Surgery ,Zhongshan Hospital of Xiamen University, Xiamen, China

Objective: To explore the clinical value of extending the culture time for accurately diagnosing hip or knee PJI.Methods: This retrospective study included 201 hip or knee PJI patients. All specimens were cultured using a standardized procedure. For all samples collected after January 2022, the extended culture period was 14 to 21 days. The detection accuracy and pathogen distribution of the standard culture duration (7 days) was compared with those extending.The overall culture positivity rate was 89.05% (179/201). The most common pathogens were coagulase-negative staphylococci (CoNS, n=54) and methicillin-resistant Staphylococcus aureus (MRSA, n=26). Extending the culture duration did not significantly increase the culture positivity rate (89.05% vs. 89.06%, P=0.997), nor did it improve the infection control rate (89.05% vs. 85.94%, P=0.526). Further study revealed that extended results did not improve the diagnosis of PJI according to the Musculoskeletal Infection Society (MSIS) criteria in most patients with both positive standard and extended culture results (82.35%, 28/34). Four of the 5 patients with only positive extended culture results were diagnosed with PJI on the basis of a single positive culture result.Extending the culture time didn't significantly improve the clinical outcomes of PJI, rate of culture positivity or polymicrobial infection detection rate.