657 - Diagnostic Utility of Dedicated Fungal Blood Cultures for Diagnosis of Candidemia

Background: Blood culture techniques have improved to the point where they are considered sensitive enough for detection of Candida. Expert guidelines clarifying the utility of use of dedicated fungal isolator cultures are lacking, and we wondered what utility, if any, they add for the diagnosis of candidemia.

Methods: All patients with cultures between March 2016-February 2020 positive for Candida were examined via manual chart review, noting time to positivity and time of initiation of antifungal therapy.

Results: We focused on cases of candidemia where a fungal culture was ordered and turned positive (59 out of the total 181 cases of candidemia).  We eliminated an additional 10 cases where fungal cultures were sent while already on antifungal therapy or in patients already known to be fungemic, given our interest in de novo diagnoses. Another case was removed due to lack of clinical details, as the patient was discharged prior to culture results and managed at a different medical facility.
There were 14 cases with discordant growth (fungal culture positive, bacterial culture negative). One patient passed away prior to culture results, but in the remaining 13 cases, the fungal culture changed clinical management, in most cases by prompting initiation of antifungal therapy.
The remaining 36 cases involved with concordant growth between bacterial and fungal cultures.  In 11 of those cases, the fungal culture isolated yeast 12 or more hours faster than its paired bacterial culture (average 40.7 +/- 26.6 hours). In 7 of these cases, the fungal culture changed management – in the remaining cases, the patient was already on empiric therapy.
Among all cultures sent in patients not receiving antifungals that isolated Candida, the overall time to positivity for fungal cultures was 37.2 +/- 13 hours, while bacterial cultures took 54 +/- 26.4 hours.Fungal Culture Results


Conclusion: Fungal cultures changed management in 20/59 cases of candidemia (34%) either by making the diagnosis faster than a bacterial culture or making it outright. Given the morbidity and mortality associated with candidemia, rapid diagnosis is critically important.  More specific guidelines optimizing how to best utilize fungal cultures to help standardize practice among clinicians will be critical going forward.