# Bacterial skin colonization with a specific Cutibacterium avidum clade as a risk factor for periprosthetic joint infections—a multicenter study

## TL;DR

A specific group of Cutibacterium avidum bacteria found on the skin is linked to joint infections after surgery, suggesting these strains may be more likely to cause disease.

## Contribution

This study identifies a distinct phylogenetic clade of Cutibacterium avidum associated with periprosthetic joint infections and reveals shared biofilm and antibiotic resistance traits.

## Key findings

- All periprosthetic joint infection isolates belong to a single phylogenetic clade of Cutibacterium avidum.
- PJI isolates show reduced bacterial fitness compared to skin isolates, potentially contributing to infection persistence.
- Rifampin is the most effective antibiotic against Cutibacterium avidum biofilms and growth.

## Abstract

Cutibacterium avidum is increasingly recognized as a
causative agent of periprosthetic joint infections (PJIs), yet data on its
pathogenic potential and distinguishing features from commensal strains
remain limited. In this multicenter study, we compared 11
C. avidum isolates from PJIs with 32
isolates from healthy skin collected across four European hospitals. We
investigated phylogenetic relationships, antibiotic susceptibility, biofilm
formation, and bacterial fitness. Phylogenomic analysis revealed two main
clades within the C. avidum population. All PJI isolates
belonged exclusively to Clade 1, which also included skin isolates. Within
Clade 1, gene content analysis showed no consistent genetic differences
between PJI and skin isolates. All isolates exhibited moderate to strong
biofilm formation, with no significant differences in either data set.
Minimal inhibitory concentration (MIC) and minimal biofilm inhibitory
concentration (MBIC) values were low and largely concordant, while minimal
biofilm eradication concentration (MBEC) values were elevated for all
antibiotics except rifampin. One isolate was resistant to clindamycin due to
the erm(X) gene. Rifampin consistently showed the lowest
MIC, minimal bactericidal concentration, MBIC, and MBEC values. Bacterial
fitness, assessed via bacterial quantitative fitness analysis, was
significantly lower in PJI isolates compared to skin isolates when all
strains were analyzed (P = 0.039), but this difference was
not statistically significant when restricted to Clade 1. In conclusion,
C. avidum isolates are strong biofilm producers
irrespective of clinical origin. PJI isolates are restricted to a single
phylogenetic clade, yet lack distinct biofilm or fitness traits within that
clade, suggesting that multiple Clade 1 strains may have the potential to
cause PJIs.

Cutibacterium avidum has long been considered a skin
commensal, but it is increasingly associated with prosthetic joint
infections (PJIs). Despite its clinical emergence, little is known about
its virulence potential or how invasive strains differ from commensal
ones. This multicenter study provides the most comprehensive comparative
analysis to date, integrating phenotypic and genomic data from both
PJI-associated and skin-derived isolates. We show that all isolates are
strong biofilm formers and that invasive isolates exhibit reduced growth
fitness—a phenotype linked to persistence and treatment failure
in other pathogens. Notably, all PJI isolates belonged to a single
phylogenetic clade, suggesting that specific lineages of C.
avidum may be more likely to cause infection. These
findings help clarify the biology of this emerging pathogen and provide
a foundation for improved diagnostics, susceptibility testing, and
future infection prevention and treatment strategies.