These authors investigated whether the genotype of Cutibacterium isolated at shoulder arthroplasty revision for periprosthetic infection is the same as the genotype of Cutibacterium isolated at the end of the primary shoulder arthroplasty in the same shoulder.
This prospective study included 156 patients undergoing primary shoulder arthroplasty. From each shoulder they obtained 5 to 12 tissue samples that were specifically cultured to detect the presence of Cutibactum.
In twenty-seven patients (17%) Cutibacterium was present at the end of the primary surgery. For each of these shoulders, DNA was extracted from the Cutibacterium isolated colonies and subjected to Whole Genome Sequencing (WGS).
Patients were followed for a minimum of two years. None of the patients with negative cultures at the index arthroplasty developed prosthetic joint infection.
Two of the 27 patients with postive cultures at the index arthroplasty developed a subsequent Cutibacterium periprosthetic shoulder infection at 6 and 4 months after the primary surgery. Both were 75 year old men. In both patients, the only microorganism present was Cutibacterium.
For the first patient, 12 cultures were obtained at the index surgery and eight of them were positive for Cutibacterium. At the revision surgery, nine cultures were obtained and eight were positive for Cutibacterium.
For the second patient, five cultures were obtained at the index surgery and only one turned to be positive for Cutibacterium. At the revision surgery, seven cultures were obtained and four were positive for Cutibacterium.
For both patients, WGS of Cutibacterium isolated colonies showed that all the isolates obtained at revision-surgery isolates were essentially the same as the isolates obtained from the shoulder at the primary arthroplasty (99.89% similarity).
They concluded that Cutibacterium present in the shoulder at the end of the primary surgery can cause periprosthetic joint infections in shoulder arthroplasty (PJI).
Comment: While there were only two patients in this study who developed PJI, both had bacteria recovered at the revision for PJI that were identical to those recovered at the index arthroplasty. It is possible that - had their followup period been longer - the number of shoulders with PJI would have been higher. See: Substantial cultures of Propionibacterium can be found in apparently aseptic shoulders revised three years or more after the index arthroplasty.
More prospective studies like this one will be helpful in confirming inoculation at the time of the index arthroplasty as the source of the bacteria that cause cases of shoulder periprosthetic infection.
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