title: Contamination of the Surgical Field with Propionibacterium acnes in Primary Shoulder Arthroplasty.
abstract: BACKGROUND
  Propionibacterium acnes is a common pathogen identified in postoperative shoulder infection. It has been shown to be present in culture specimens during primary shoulder arthroplasty; however, recent work has suggested that it is most likely to be a contaminant. Our aim was to identify the potential sources of contamination in shoulder arthroplasty.
  
  
  METHODS
  Tissue swabs were obtained for microbiological analysis from consecutive patients undergoing primary shoulder arthroplasty. Routine surgical technique was maintained, and 5 specimens were taken from different sites: (1) the subdermal layer, (2) the tip of the surgeon's glove, (3) the inside scalpel blade (used for deeper incision), (4) the forceps, and (5) the outside scalpel blade (used for the skin incision).
  
  
  RESULTS
  Forty patients (25 female patients and 15 male patients) were included. Thirteen (33%) of the 40 patients had at least 1 culture specimen positive for P. acnes. Two (8%) of the 25 female patients and 11 (73%) of the 15 male patients had ≥1 culture specimen positive for P. acnes. The most common site of growth of P. acnes was the subdermal layer (12 positive samples), followed by the forceps (7 positive samples), the tip of the surgeon's glove (7 positive samples), the outside scalpel blade (4 positive samples), and the inside scalpel blade (1 positive sample). There were 27 of 75 swabs that were positive on culture for P. acnes in male patients compared with 4 of 125 swabs in female patients. Male patients had 66 times (95% confidence interval, 6 to 680 times) higher odds of having a positive culture indicating subdermal colonization compared with female patients (p < 0.001).
  
  
  CONCLUSIONS
  P. acnes is a common contaminant of the surgical field in primary shoulder arthroplasty. The subdermal layer may be the source of this contamination, and the prevalence of P. acnes in the surgical wound may be due to the surgeon's manipulation with gloves and instruments. Our findings are consistent with those regarding the increased rates of P. acnes bacterial load and intraoperative growth in male patients compared with female patients.
  
  
  CONCLUSIONS
  P. acnes is likely to be spread throughout the surgical field from the subdermal layer via soft-tissue handling by the surgeon and instruments. Strategies need to be utilized to minimize this contact and to reduce the chance of colonization.
authors.affiliation: Perth Orthopaedic & Sports Medicine Center, West Perth, Australia ssri@sydneyshoulder.com.au.
authors.forename: Travis M
authors.initials: TM
authors.lastname: Falconer
authors.affiliation: Specialty Orthopaedics, Bella Vista, Australia.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Baba
authors.affiliation: Sydney Shoulder Research Institute, St. Leonards, Australia.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Kruse
authors.affiliation: Sydney Shoulder Research Institute, St. Leonards, Australia.
authors.forename: Oscar
authors.initials: O
authors.lastname: Dorrestijn
authors.affiliation: Sydney Shoulder Research Institute, St. Leonards, Australia.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Donaldson
authors.affiliation: Raymond Purves Bone and Joint Research Laboratory, Kolling Institute of Medical Research (M.M.S.), and Microbiology Department (M.C.F. and B.J.H.), Royal North Shore Hospital, St. Leonards, Australia.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Smith
authors.affiliation: Raymond Purves Bone and Joint Research Laboratory, Kolling Institute of Medical Research (M.M.S.), and Microbiology Department (M.C.F. and B.J.H.), Royal North Shore Hospital, St. Leonards, Australia.
authors.forename: Melanie C
authors.initials: MC
authors.lastname: Figtree
authors.affiliation: Raymond Purves Bone and Joint Research Laboratory, Kolling Institute of Medical Research (M.M.S.), and Microbiology Department (M.C.F. and B.J.H.), Royal North Shore Hospital, St. Leonards, Australia.
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Hudson
authors.affiliation: Sydney Shoulder Specialists, St. Leonards, Australia.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Cass
authors.affiliation: Sydney Shoulder Specialists, St. Leonards, Australia.
authors.forename: Allan A
authors.initials: AA
authors.lastname: Young
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000072228:Arthroplasty, Replacement, Shoulder / Q000009:adverse effects*; D005260:Female; D016908:Gram-Positive Bacterial Infections / Q000209:etiology* / Q000382:microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000382:microbiology; D011425:Propionibacterium acnes / Q000302:isolation & purification*; D012785:Shoulder Joint / Q000382:microbiology / Q000601:surgery*; D012867:Skin / Q000382:microbiology*