The purpose of this study was to further evaluate the pathogenicity of hemolytic and nonhemolytic phenotypes of Propionibacterium acnes (P acnes) isolates from shoulders of orthopaedic patients.
Thirty-one patient records were reviewed, which had a positive P acnes shoulder culture from joint aspiration fluid and/or intraoperative tissues for demographics, clinical course, culture, and laboratory data. Patients were categorized as definite infection, probable infection, or probable contaminant. Antibiotic resistance patterns and hemolysis characteristics were subsequently analyzed.
Hemolysis demonstrated 100% specificity with a positive predictive value of 100% and 80% sensitivity with a negative predictive value of 73% for determining definite and probable infections. Hundred percent of the patients in the hemolytic group and only 27% of patients in the nonhemolytic group were classified as infected. Presenting inflammatory markers were markedly higher in the hemolytic group. Clindamycin resistance was found in 31% of the hemolytic strains, whereas no antibiotic resistance was observed in the nonhemolytic group.
Hemolytic strains of P acnes exhibit enhanced pathogenicity to their host by eliciting a more prominent systemic inflammatory response, increased antibiotic resistance, and a more challenging clinical course. Hemolysis may serve as a specific marker for assisting in diagnosing true infection with P acnes.
Level III retrospective comparative study.
From the Department of Orthopaedics (Dr. Boyle, Mr. Wright, and Dr. Duquin), State University of New York at Buffalo, the Department of Microbiology and Immunology (Dr. Crane), State University of New York at Buffalo, Buffalo, NY, and the Division of Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, New York, NY (Dr. Nodzo).
Correspondence to Dr. Boyle: email@example.com
Dr. Duquin or an immediate family member is a member of a speakers' bureau or has made paid presentations on behalf of Zimmer Biomet; serves as a paid consultant to Zimmer Biomet; and has received research or institutional support from Zimmer Biomet. None of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Boyle, Dr. Nodzo, Mr. Wright, and Dr. Crane.