Orthopedic-service cultures show 2018–2025 resistance proxies, not infection incidence

A single-center surveillance study of 7,385 culture-positive isolate records submitted by orthopedic services found a broad range of bacterial pathogens and identified downward unadjusted trends in two selected antimicrobial-resistance proxies between 2018 and 2025. The results describe laboratory isolate records rather than confirmed orthopedic infections, so they should not be interpreted as an estimate of infection incidence or, on their own, as a basis for empirical-treatment policy.

The retrospective study examined records submitted from January 2012 through December 2025. Its main analysis was record-level rather than patient-level and included wound and musculoskeletal-related specimens as well as blood, urinary and respiratory samples. Gram-negative bacteria accounted for 4,214 records, or 57.1%, and Gram-positive bacteria accounted for 2,905, or 39.3%. Staphylococcus aureus was the most frequently identified organism, appearing in 1,614 records (21.9%), followed by Escherichia coli in 836 (11.3%) and Pseudomonas aeruginosa in 831 (11.3%).

Specimen source varied substantially across the dataset. After the investigators verified historical specimen coding, wound secretion accounted for 5,504 records, or 74.5% of all analyzed isolates. The findings therefore characterize the microbiology of cultures submitted by orthopedic services, not the organisms found exclusively in clinically confirmed orthopedic infections. The authors noted that source-specific variation matters for local antibiogram development, because a hospital-wide antibiogram may not represent every specimen category associated with orthopedic-service care.

Susceptibility data were not consistently available throughout the 14-year study period. For that reason, the investigators evaluated selected phenotypic resistance proxies only among 2018–2025 records with an evaluable tested denominator. The analysis reported Wilson 95% confidence intervals and used exploratory trend tests. Among the evaluable tested S. aureus isolates, the MRSA phenotype-proxy proportion decreased from 51.4% in the first assessed period to 27.0% in the final period. A downward unadjusted trend was also observed for the phenotypic carbapenem-resistance proxy among Klebsiella pneumoniae records.

Those trends do not establish that resistance declined because of a particular hospital intervention, nor do they provide a causal explanation for the observed changes. The analysis was retrospective, confined to one center and based primarily on isolate records rather than linked patient outcomes. The researchers also described the resistance analysis as exploratory. Accordingly, the clearest finding is a change in measured phenotype-proxy proportions over the 2018–2025 assessment window, rather than a demonstrated reduction in resistance across a defined orthopedic-infection population.

Estimates for other organisms were more limited. The phenotypic carbapenem-resistance proxy for Acinetobacter baumannii remained high among A. baumannii-labelled evaluable records, but records labeled as A. baumannii complex were not included in that denominator. Annual estimates for the carbapenem-resistant P. aeruginosa proxy were constrained by small numbers of tested isolates. These differences in denominator size and organism labeling limit direct comparison among the selected resistance proxies and require the caution built into the study’s record-level design.

To assess the influence of repeated isolates, the researchers conducted a sensitivity analysis that retained the first isolate obtained within a 30-day period. The MRSA and carbapenem-resistant K. pneumoniae trend signals persisted under this restriction. The check indicates that the findings were not dependent solely on the inclusion of repeat submissions, although it cannot resolve the broader limitations of a single-center retrospective dataset. It also does not convert record-level surveillance into evidence about individual patient risk or clinical outcomes.

A separate chart-review substudy examined 100 recent wound or musculoskeletal-related records to assess clinical relevance and culture-informed management. Reviewers judged 96 of the 100 records to represent infections. Among 91 records for which the treatment-management assessment was evaluable, antimicrobial treatment was adjusted in response to culture information in 64 cases. This substudy shows that culture results sometimes influenced management, but it did not test whether any particular treatment strategy improved outcomes. Overall, the surveillance data can support development or updating of a source-stratified local orthopedic antibiogram and inform antimicrobial-stewardship review, while remaining insufficient to estimate population-level orthopedic-infection incidence or determine empirical treatment by themselves.

Subject of Research: Surveillance of bacterial pathogens and selected antimicrobial-resistance proxies in orthopedic-service culture-positive isolate records

Article Title: Pathogen distribution and selected phenotypic resistance trends in orthopedic-service culture-positive isolate records: a 14-year single-center surveillance study

Article References: Xie, B.-L., Nie, L.-Z., Zhang, W., Zhang, B., & Guo, R.-S. (2026). Pathogen distribution and selected phenotypic resistance trends in orthopedic-service culture-positive isolate records: a 14-year single-center surveillance study. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14367-3

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14367-3

Keywords: orthopedic infections, culture-positive isolates, antibiotic resistance, MRSA, CRKP, antibiogram, hospital surveillance, antimicrobial stewardship, clinical microbiology, record-level analysis, Pathogen, distribution