699. A Combination of Prolonged Anaerobic Bacterial Incubation and Multiple Cultures Altered Clinical Management  of Skin Flora Prosthetic Joint Infections (PJI)
Session: Poster Abstract Session: Skin, Soft Tissue and Joint Infections
Friday, October 21, 2011
Room: Poster Hall B1
Background: Two challenges in prosthetic joint revisions are defining whether cultured skin bacteria are pathogens, and managing negative cultures when infection is clinically evident. To address these problems we examined the clinical impact of introducing a technique of multiple cultures combined with prolonged anaerobic bacterial incubation for prosthetic joint revision.

Methods:  A technique of ≥5 separate peri-prosthetic joint tissue biopsies was initiated. Samples were sent for bacterial culture, with 10 day anaerobic incubation. The diagnosis of PJI was made using microbiology, pathology, clinical and x-ray data.   To understand the clinical impact of the new technique, a retrospective chart review was undertaken of patients who underwent prosthetic joint revision using the technique.   Coagulase negative Staphylococcus, Corynebacteria or Propionibacteria were defined as skin flora.   Infection with skin flora was defined as ≥3 of 5 biopsies that grew the same skin flora organism, and the patient was treated for infection.  Contamination was defined as 1- 2 of 5 biopsies that grew the same skin flora organism, and were ignored clinically. Prolonged incubation provided the diagnosis if organisms grew  days 4-10 of incubation & were managed as infection. Culture data was compared to clinical and pathology results.  Patient outcomes were reviewed 6 to 12 months post-operatively.

Results:  36 prosthetic joint revision cases were identified where ≥5 biopsies were taken.  

8 cases  grew the same skin flora organism from 1 or 2 biopsies and were not treated. In follow-up 5/8  untreated cases had no recurrence (suggesting true contaminants), 1/8 cases  had recurrent infection, 2/8 cases were lost to follow-up.  Thus the technique identified 5 definite cases of contamination. 

4  cases grew the same skin flora organism from ≥3 biopsies  and were managed as infection.  Prolonged anaerobic incubation grew  Propionibacteria in 2/4 of these cases.   

The technique therefore appropriately altered management in 9/36 cases (5 contaminant cases avoided antibiotics & 4 infections were identified and treated)

Conclusion: Introduction of this technique into clinical practice  affected management in 25% of prosthetic joint revision cases in which it was used.


Subject Category: D. Diagnostic microbiology

Alexander DeHaan, MD1, Michael Kuhne, MD1, Kimberly Felder, PA-C2, Yee Doung, MD1, Thomas Huff, MD1, Alex Herzberg, MD1, Adam Mirarchi, MD1, Robert Orfaly, MD1, James Hayden, MD Ph.D1, Kathryn Schabel, MD1 and Penelope Barnes, MBBS, Ph.D1,2, (1)Orthopaedics and Rehabilitation, Oregon Health and Sciences University, Portland, OR, (2)Infectious Disease, Oregon Health Sciences University, Portland, OR

Disclosures:

A. DeHaan, None

M. Kuhne, None

K. Felder, None

Y. Doung, None

T. Huff, None

A. Herzberg, None

A. Mirarchi, None

R. Orfaly, None

J. Hayden, None

K. Schabel, None

P. Barnes, None

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