Moraxella osloensis Isolated from the Intraoperative Field After Reverse Total Shoulder Arthroplasty

Moraxella osloensis is an infrequently reported component of the human skin microbiota, but it has recently been recognized as a potential source of intraoperative contamination. Its pathogenic role remains poorly defined, particularly in shoulder arthroplasty. This study describes the recovery and characterization of M. osloensis from intraoperative periprosthetic tissue samples collected immediately after reverse total shoulder arthroplasty in five patients. All isolates exhibited low colony counts (10-50 CFU/mL), were uniformly susceptible to the antimicrobial agents tested, and did not produce β-lactamases. Biofilm formation-an important virulence determinant in periprosthetic joint infections-was detected in two of the five isolates. Clinically, no patient developed postoperative infection within 12 months, and only one experienced a transient superficial wound-healing delay, which resolved with a short administration of oral antibiotics. These findings indicate that M. osloensis may be present in the operative field despite stringent skin preparation and aseptic protocols, likely reflecting endogenous colonization rather than environmental contamination. Although its clinical impact appears limited in this context, the bacteria's biofilm-forming potential and underrecognized presence in the operating room underscore the importance of continued surveillance and careful interpretation when isolated from surgical specimens.