Rethinking Fungal Blood Cultures in Sepsis Workups
Logan Brock, PharmD, presents data at MAD-ID, showing limited diagnostic yield from routine fungal cultures and delayed results compared with standard methods.
A retrospective analysis from UF Health Shands Hospital questions the clinical value of routinely ordering fungal blood cultures alongside standard blood cultures during initial sepsis evaluations. The findings, presented by Logan Brock, PharmD, at MAD-ID 2025, show that fungal blood cultures rarely provide additional diagnostic information and take longer to yield results.
The single-center study reviewed 2,073 adult inpatient encounters from January 1, 2023, to December 31, 2024, in which fungal and standard blood cultures were collected within 24 hours of each other. Of those, 96.9% showed no growth in either type of culture. Among the 64 pairs that did show growth, only 8 (12.5%) fungal cultures were positive when standard cultures were negative. Conversely, 30 (46.9%) standard cultures identified fungal pathogens that fungal cultures missed. Both cultures were positive in 26 (40.6%) cases. Candida species accounted for 93.8% of all fungal isolates.
Median time-to-positivity was significantly longer for fungal cultures (48 hours; IQR: 41–93) than for standard cultures (33 hours; IQR: 28–43; p < 0.001). All-cause in-hospital and 30-day mortality rates were 17.4% and 16.4%, respectively.
“Paired fungal blood cultures infrequently identified fungal pathogens not detected by standard blood cultures and had a longer time-to-positivity,” the authors concluded.
Logan Brock, a PGY-2 infectious diseases pharmacy resident at UF Health Shands, said the study originated from concerns raised by an ICU pharmacist, “One of our ICU pharmacists reached out to us because she was seeing an increase in fungal blood cultures being ordered at our hospital. So, us and the ID stewardship department did a little digging with her, and we confirmed that there were actually a lot of fungal blood cultures being ordered. Anecdotally, we weren’t seeing a lot of fungal growth from these fungal blood cultures. Even in the cases where they did grow, the standard blood cultures were also growing the fungus. So, we wanted to take a closer look at our hospital’s fungal blood culture ordering and see if they’re providing any utility—or perhaps not.”
While no formal restrictions have been implemented yet, Brock says discussions are underway, “Full disclosure—at my hospital, we haven’t decided how we’re going to restrict fungal blood cultures based on the results of this study. There are a lot of key stakeholders that will have to get engaged—ID physicians, ICU doctors who are ordering the fungal blood cultures.”
He noted that one possible model could mirror how the hospital managed anaerobic blood culture bottles during a supply shortage, “Some ideas we’ve been talking about are doing something similar to what we did with our anaerobic blood culture bottles during the shortage… so that any people or teams who wanted to order anaerobic bottles had to request them from the micro lab—and usually had to show that they had some indication for them, like intra-abdominal infections… I can see doing something similar for fungal blood cultures.”
A Case Where It Mattered
Despite the low yield overall, Brock emphasized that fungal blood cultures may still be valuable in select high-risk patients. He shared one case in which they led to a meaningful therapeutic adjustment.
“Yeah, so there was actually one case in particular where fungal blood cultures provided a really big benefit, I would say. This was a 73-year-old patient who came in septic. He had a bowel perforation, so he was started on fungal coverage. Predictably and appropriately, standard blood cultures were drawn, fungal blood cultures were drawn, and the standard blood cultures grew a couple of bacteria—E. coli and Globicatella sanguinis—but did not grow any fungus.
“The fungal blood culture did actually grow a Candida glabrata, and the fluconazole MIC for that glabrata ended up being 32, which is susceptible dose-dependent. It is susceptible, but it’s right at the breakpoint for susceptible—so it’s a very high MIC.
“Based on those results, we switched him from fluconazole to our echinocandin at our hospital, micafungin, which I think was a much better therapy. Their white count came down, they improved, and I think without using fungal blood cultures there, we might not have known they had a fungal infection at all.” The findings support targeted, rather than routine, use of fungal blood cultures, especially in patients without clear risk factors for invasive fungal disease
