Correlation between hemolytic profile and phylotype of <i>Cutibacterium acnes</i> (formerly <i>Propionibacterium acnes</i>) and orthopedic implant infection.

Abstract

<i>Cutibacterium acnes</i> is a recognized culprit for implant-associated infections, but positive cultures do not always indicate clinically relevant infection. Studies have shown a correlation between the β-hemolytic phenotype of <i>C. acnes</i> and its infectious capacity, but correlation with genetic phylotype has not been performed in literature. The purpose of this study is to evaluate β-hemolysis phenotype, genetic phylotype, and mid-term clinical outcomes of <i>C. acnes</i> isolated from orthopedic surgical sites. Fifty-four <i>C. acnes</i> isolates previously obtained from surgical wounds of patients undergoing hip, knee, shoulder, or spine implant removal were re-cultured. There were 21 females and 33 males with an average age of 59 years (range, 18-84). Twenty-four were from clinically infected sites whereas 30 were considered contaminants. De novo β-hemolysis was analyzed and a retrospective chart review was performed to evaluate clinical outcomes at 7.1 years (range, 0.1-12.8). On <i>Brucella</i> agar with 5% rabbit blood, 46% of contaminant and 43% of infectious isolates were hemolytic. Type II phylotype was significantly more nonhemolytic regardless of infectious or contaminant status (p < 0.05). Type 1B correlated with a hemolytic-infectious phenotype and Type 1A with a hemolytic-contaminant phenotype but was not statistically significant. The β-hemolytic profile of <i>C. acnes</i> did not correlate with phylotype or clinically relevant orthopedic infection.