Low Yield of Routine Fungal Culture from Periprosthetic Joint Specimens

BACKGROUND: Prosthetic joints may fail for a variety of reasons, including infection, which are estimated to occur in 1–2 percent of joint replacements. Bacterial and fungal cultures are commonly ordered on the same specimens, despite the rarity of fungal prosthetic joint infections. To evaluate the yield of fungal cultures from specimens collected from prosthetic joint revision procedures, we performed a retrospective analysis of culture positivity for orthopedic surgical specimens submitted for culture at our institution. METHODS: Microbiology culture results for all orthopedic surgical specimens collected from January 2016 through February 2017 were obtained from a laboratory information system. Bacterial and fungal culture results for each patient were matched by MRN, date of specimen collection and accession number. Culture positivity was defined as growth of any microorganism on any piece of media used for bacterial or fungal media per each specimen submitted for culture. RESULTS: Over a 14-month period, 888 cultures from 189 unique surgical events (unique date/MRN) were submitted for bacterial culture. On average, 5 specimens were submitted per patient (range 1–11). Of these, 352 specimens (40%) were positive for bacterial growth. Ninety-seven percent of specimens submitted for bacterial culture had a corresponding fungal culture ordered. Only 1 of the 861 fungal cultures ordered was positive for fungal growth (0.1%). One specimen from a shoulder revision grew Aureobasidium pullulans, a ubiquitous fungus that is a rare human pathogen. Direct exam of the specimen revealed no PMNs or organisms. No A. pullulans was isolated from eight other cultures from the same procedure. This organism was likely viewed as a contaminant as no anti-fungal therapy was initiated. CONCLUSION: Over a recent 14-month period at our institution, the yield of fungal culture of orthopedic surgical specimens was exceedingly low (0.1% positivity). Importantly, yeasts such as Candida species, can readily grow on bacterial culture media, especially if incubation times are extended. Therefore, fungal culture from periprosthetic joint specimens should be limited unless there is a strong clinical suspicion of fungal infection. DISCLOSURES: All authors: No reported disclosures.