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Hemolytic strains of Propionibacterium acnes do not demonstrate greater pathogenicity in periprosthetic shoulder

Jared M Mahylis¹, Vahid Entezari¹, James Karichu²

¹Department of Orthopaedic Surgery, Orthopaedic and Rheumatologic Institute, Cleveland Clinic, Cleveland, OH, USA.

Journal of Shoulder and Elbow Surgery

|February 24, 2018

Abstract

Background:

Hemolysis has been suggested as a feature conferring increased pathogenicity to certain Propionibacterium acnes strains in the setting of shoulder infection. The purpose of this study was to compare the virulence of hemolytic and nonhemolytic P acnes strains in patients undergoing revision shoulder arthroplasty.

Methods:

Thirty-nine patients with at least 1 positive culture growth for P acnes at the time of revision surgery were identified with P acnes isolates available for hemolysis testing. Patients were grouped into those with P acnes isolates positive (n = 20) and negative (n = 19) for hemolysis. The groups were retrospectively compared based on objective perioperative findings around the time of revision surgery and the postoperative clinical course, including the need for revision surgery. All cases were classified into categories of infection (definite infection, probable infection, and probable contaminant) based on objective perioperative criteria.

Results:

The presence of hemolysis was not significantly associated with an increased likelihood of infection (P = .968). Hemolysis demonstrated a 75% sensitivity and 26% specificity for determining infection (definite infection and probable infection categories). The hemolytic and nonhemolytic groups showed no difference regarding preoperative serum erythrocyte sedimentation rate and/or C-reactive protein level (P = .70), number of positive cultures (P = .395), time to positive culture (P = .302), and presence of positive frozen section findings (P = .501). Postoperatively, clindamycin resistance, shoulder function, and the rate of reoperation were not significantly different between the hemolytic and nonhemolytic groups.

Conclusion:

The presence of hemolysis was not associated with increased pathogenicity in patients with P acnes-positive cultures following revision shoulder arthroplasty, when assessed by objective perioperative criteria and the postoperative clinical course.

Insights

Hemolysis in Propionibacterium acnes (P. acnes) did not increase pathogenicity in shoulder revision arthroplasty patients. This study found no significant difference in infection rates or clinical outcomes between hemolytic and nonhemolytic P. acnes strains.

Area of Science:

Orthopedic Surgery
Infectious Disease
Microbiology

Background:

Hemolysis is a proposed virulence factor for Propionibacterium acnes (P. acnes) in shoulder infections.
P. acnes is a common cause of infection in shoulder arthroplasty, particularly in revision cases.

Purpose of the Study:

To compare the virulence of hemolytic and nonhemolytic P. acnes strains in patients undergoing revision shoulder arthroplasty.
To determine if hemolysis is associated with increased pathogenicity of P. acnes in this patient population.

Main Methods:

Retrospective comparison of 39 patients with P. acnes-positive cultures undergoing revision shoulder arthroplasty.
Patients were grouped based on hemolysis testing of P. acnes isolates (n=20 hemolytic, n=19 nonhemolytic).
Comparison included perioperative findings, infection classification, and postoperative clinical course.

Main Results:

Hemolysis was not significantly associated with an increased likelihood of P. acnes infection (P=.968).
Hemolysis showed 75% sensitivity and 26% specificity for infection.
No significant differences were observed between hemolytic and nonhemolytic groups in preoperative inflammatory markers, culture results, frozen section findings, postoperative shoulder function, or reoperation rates.

Conclusions:

Hemolysis in P. acnes does not appear to increase pathogenicity in patients with P. acnes-positive cultures undergoing revision shoulder arthroplasty.
Objective perioperative criteria and postoperative clinical outcomes did not support hemolysis as a marker for increased virulence in this context.

Read full analysis

Keywords:

Propionibacterium acnes diagnosis periprosthetic joint infection revision shoulder arthroplasty β-hemolysis

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