Patients with hip osteoarthritis may have differences in selected intra-articular taxa and greater representation of lipopolysaccharide-related functions compared with nonarthritic controls, although overall microbial community structure may not differ by diagnosis.
In a prospective cohort study, researchers enrolled 48 patients undergoing hip arthroplasty between December 2021 and June 2022. After excluding 8 patients with incomplete medical records, they included 20 patients with primary hip osteoarthritis and 20 with intracapsular femoral neck fracture who served as nonarthritic controls.
The researchers collected 120 synovial fluid, femoral head cartilage, and acetabular fossa specimens and performed 16S ribosomal RNA gene sequencing. High-quality sequencing results were available for 59 of the 120 specimens. Acetabular fossa specimens were excluded from subsequent statistical analyses because just 2 met all filtering criteria. The researchers evaluated differences in relative taxonomic abundance with Wilcoxon rank sum testing and applied Benjamini-Hochberg correction.
Among 4 alpha-diversity measures, only the Simpson index differed by diagnosis, with reduced evenness in osteoarthritis specimens. Beta diversity differed by specimen type across all 4 evaluated metrics but did not differ by diagnosis. At the phylum level, Proteobacteria and Firmicutes differed between osteoarthritis and fracture specimens. At the genus level, Pseudomonas, Atopostipes, and Staphylococcus differed by diagnosis.
Functional prediction showed enrichment of the KDO2-lipid A biosynthesis pathway in osteoarthritic specimens. Within Pseudomonas, predicted median abundances of LPXB, LPXL, LPXM, and K00973 were higher in osteoarthritis specimens and nearly absent in controls.
The researchers cautioned that the 40-patient cohort, low-biomass specimens, and potential contamination limited interpretation. Pseudomonas and Staphylococcus may represent sequencing contaminants, and their detection did not establish the presence of living bacteria or colonization. The cross-sectional analysis could not determine the temporal or mechanistic relationship between the microbial DNA signatures and osteoarthritis progression. In addition, functional analyses were inferred from 16S ribosomal RNA data rather than measurements of transcription or protein activity.
“[T]he [osteoarthritis]-related signal appears to be more selective, involving specific taxonomic differences and predicted functional enrichment of lipopolysaccharide-related pathways, rather than large-scale restructuring of the intra-articular microbiome,” wrote primary authors Pablo A. Slullitel, MD, of the “Sir John Charnley” Hip Surgery Unit in the Institute of Orthopaedics “Carlos E. Ottolenghi” at the Italian Hospital of Buenos Aires and Florencia A. Lohmann, MD, of the Institute of Translational Medicine and Biomedical Engineering of the National Scientific and Technical Research Council at the University Hospital Italiano Buenos Aires, and colleagues.
The study received funding from a 2021 Société Internationale de Chirurgie Orthopédique et de Traumatologie research grant and institutional support from the Center of Translational Medicine and Biomedical Engineering. Full disclosures can be found in the study.
Source: JBJS Open Access
