Staphylococcus aureus and coagulase-negative staphylococci in knee periprosthetic joint infection: temporal trends and inflammatory profiles in a seven-year single-center study from Taiwan

The microbiological profile of periprosthetic joint infection (PJI) after total knee arthroplasty is heterogeneous, with Staphylococcus aureus and coagulase-negative staphylococci (CoNS) among the most frequently isolated pathogens. Pathogen distribution varies across institutions and may not be static over time, yet contemporary knee-specific data from Asian populations are scarce, and whether these two pathogens have distinct inflammatory profiles remains unclear. We retrospectively reviewed all surgically treated knee PJI episodes at a Taiwanese tertiary referral center between January 2017 and December 2023. The primary analysis examined temporal trends in the annual proportions of S. aureus and CoNS, tested by the Cochran–Armitage trend test with all PJI episodes as the denominator. The secondary analysis compared serum inflammatory markers and synovial fluid parameters between monomicrobial S. aureus and CoNS infections, with adjustment for age, sex, and Charlson Comorbidity Index. Trends in infection categories and methicillin resistance subgroups were supporting analyses. Among 164 episodes, S. aureus (30.5%) and CoNS (19.5%) were the most frequently isolated pathogens. The annual proportion of CoNS episodes rose from 7.7% (1/13) in 2017 to 27.6% (8/29) in 2023 ( P = 0.031; adjusted odds ratio per calendar year, 1.278; 95% confidence interval [CI], 1.020–1.600; P = 0.032), with no significant decline in S. aureus . Infection categories and methicillin resistance subgroups showed no significant temporal trend, although annual case numbers were small. In unadjusted analyses, CoNS infections showed lower C-reactive protein levels, erythrocyte sedimentation rates, and synovial fluid white blood cell (WBC) counts than S. aureus infections. After adjustment, only the lower synovial fluid WBC count remained independently associated with CoNS infection (β = −1.065; 95% CI, − 1.766 to − 0.364; P = 0.004). The proportion of CoNS episodes rose over seven years among surgically treated knee PJIs at this Taiwanese center, with no significant decline in S. aureus . Monomicrobial CoNS infections were associated with lower synovial fluid WBC counts than S. aureus infections. These findings support continued institution-specific surveillance and indicate that species-related differences in synovial fluid WBC counts merit prospective evaluation.