Saturday, February 24, 2018

Propionibacterium - resistance to clindamycin

Propionibacterium acnes Susceptibility and Correlation with Hemolytic Phenotype

These authors tested the antibiotic susceptibility and hemolytic activity of 106 P. acnes strains from sterile body sites (i.e. not from infections) collected at their medical center.
14 were hemolytic and 83 were not.

 They found that 9% of the strains were resistant to clindamycin and that there was an association between those phenotypes that were hemolytic on Brucella Blood Agar and clindamycin resistance.

Comment: This study again points out that all Propionibacterium are not the same. Some strains are hemolytic and some are clindamycin resistant. In shoulder arthroplasty prophylaxis and in the treatment of shoulder arthroplasty infections, antibiotics other than clindamycin may be preferable.

This article should be contrasted with

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

in which 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.

In this study 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.

These authors concluded that 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.

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