Antimicrobial resistance profiles in septic arthritis of native knee and shoulder joint from 2007 to 2024: a single center retrospective study

Jennifer Straub^*Laurenz WillmannDaniel LeeJoachim OrtmayrKevin StaatsReinhard WindhagerChristoph Böhler^*

• Medical University of Vienna, Vienna, Austria

Abstract Introduction Septic arthritis of large joints is associated with high morbidity and mortality, necessitating prompt empiric antibiotic therapy tailored to local and current pathogen patterns. The need for antimicrobial stewardship further highlights the importance of updated data on pathogens and resistance trends to guide effective empiric treatment. Methods This study retrospectively investigated the distribution of causative pathogens and their antimicrobial resistance profiles in septic arthritis of native knee and shoulder joints from January 2007 to December 2024 at a tertiary hospital. A total of 326 patients who met the modified Newman Criteria and had confirmed culture results with antimicrobial susceptibility data were included. Cases involving prosthetic joints, treatment initiated at other facilities, or incomplete records were excluded. Cases were grouped into three six-year intervals to evaluate temporal trends in pathogen distribution and antimicrobial resistance. Results Staphylococcus aureus was the predominant pathogen with 16 cases (51,61%) from 2007 - 2012, 25 (43,10%) from 2013-2018, and 23 (48,94%) from 2019-2024 . Only six cases of Methicillin-resistant S. aureus (MRSA) were identified overall (4,41%). Other coagulase-negative staphylococci aside from Staphylococcus epidermidis decreased over time to 1 case (2,13 %) from 2019 to 2024, while rates of gram-negative rods remained stable at about 10% over time. Enterococcal infections were rare, with only one case (0,74%), and there was only a single fungal infection (0,74%). A significant decline in resistance to Penicillin G was observed (p=0,004), along with significant variations in clindamycin susceptibility, which showed a peak in resistance from 2013-2018 at 40,82% (p=0.014). Methicillin-sensitive S. aureus predominated in younger adults 18–64 years (51,56%), whereas Streptococcus spp. were more frequent in patients over 65 years. Discussion Our data support the empirical use of narrow spectrum beta-lactams for septic arthritis of the knee and shoulder. MRSA and gram-negative infections were rare, and high clindamycin resistance highlights the need to reconsider its routine use in patients with suspected penicillin allergy, emphasising the need for antibiotic stewardship based on local pathogen and susceptibility distributions.