Propionibacterium avidum as an Etiological Agent of Prosthetic Hip Joint Infection

Abstract

Propionibacterium acnes is well-established as a possible etiologic agent of prosthetic joint infections (PJIs). Other Propionibacterium spp. have occasionally been described as a cause of PJIs, but this has not previously been the case for P. avidum despite its capacity to form biofilm. We describe two patients with prosthetic hip joint infections caused by P. avidum. Both patients were primarily operated with an anteriorly curved skin incision close to the skin crease of the groin, and both were obese. Initial treatment was performed according to the DAIR procedure (debridement, antibiotics, and implant retention). In case 1, the outcome was successful, but in case 2, a loosening of the cup was present 18 months post debridement. The P. avidum isolate from case 1 and two isolates from case 2 (obtained 18 months apart) were selected for whole genome sequencing. The genome of P. avidum obtained from case 1 was approximately 60 kb larger than the genomes of the two isolates of case 2. These latter isolates were clonal with the exception of SNPs in the genome. All three strains possessed the gene cluster encoding exopolysaccharide synthesis.P. avidum has a pathogenic potential and the ability to cause clinically relevant infections, including abscess formation, in the presence of foreign bodies such as prosthetic joint components. Skin incision in close proximity to the groin or deep skin crease, such as the anteriorly curved skin incision approach, might pose a risk of PJIs by P. avidum, especially in obese patients.

Clinical and Biological Features of Cutibacterium (Formerly Propionibacterium)avidum, an Underrecognized Microorganism

“…Figure 2 shows a significant relatedness among seven genomes, with orthoANI values between 98.4 and 100%. I can, however, also highlight the presence of a cluster including two genomes (C. avidum DPC6544 and UCP-PD2), which might constitute a subpopulation or a subtype of this species, as recently suggested (14,49). These data should be investigated further with more diverse and numerous clinical isolates to better investigate C. avidum pathogenicity, but also the group or cluster delineation of strains with specific potential for abscess formation, for example, or biofilm production, as previously reported for the C. acnes phylotype groups (50-52).…”

“…C. avidum is characterized by the production of an exopolysaccharide-like structure, encoded by a targeted region corresponding to a species-specific genomic island. This region harbors more than 30 genes, including 19 encoding glycosyltransferases and enzymes implicated in mono-or polysaccharide modification (14). In contrast, C. granulosum is able to produce pilus-like structures, appendices that have never been described for either C. avidum or C. acnes.…”

“…Following the culture-centric period, which focused on developing new tools to better understand bacterial growth, metabolism, and immunogenicity, we are now entering a new genomic era. This new period will allow us to decipher virulence factors, genome organization, genome plasticity, and specific features of several C. avidum clinical strains by using nextgeneration sequencing (13,14) and confirming hypotheses through various in vitro and in vivo models. As a result, deeper genomic analyses and comparisons will provide key information about the organism's phylogeny and the potential existence of subpopulations within this species.…”

“…Although a whole-genome synteny has been reported for propionibacteria originating from the skin, a certain plasticity of the genome has revealed C. avidum-specific genomic regions. This observation demonstrated the importance of these genomic regions, which include exopolysaccharide gene synthesis functions, prophage regions, and other gene-specific clusters involved in diverse fitness, survival, and defense functions (14). Although only 2 of 14 complete genomes are publicly available, C. avidum genomic studies remain relevant to furthering the understanding of the pathogenesis of this organism.…”

“…Although often defined as a commensal (12,13), C. avidum has likely been underestimated, unrecognized, and misidentified in more than a few clinical cases. Despite its low frequency in human infections, numerous associated or invasive infections have been reported: bone infections, infective endocarditis (IE), breast infections, abdominal infections, prostate infections, and splenic and skin abscesses have been described, sometimes with significant collateral damage for the patient (14)(15)(16)(17). In my experience, although one cannot avoid bias according to the identification method used and the awareness of microbiologists, there has been a clearly observed increase in C. avidum-positive samples over the past years.…”