"What am I?" microbiology of culture-positive, biofire® blood culture identification 2 panel-negative bloodstream infections.

BACKGROUND

The BioFire® blood culture identification 2 panel (BCID2) detects 33 of the most common bloodstream infection (BSI) pathogens, yet it can fail to detect the causal agent of sepsis in up to 13 % of cases, mostly due to infections caused by off-panel target microorganisms. A better understanding of the microbiology of culture-positive, BCID2-negative BSI is needed.

METHODS

Single-center, retrospective study of microbiology and outcomes in 275 cases of BCID2-negative BSI between 2022 and 2024.

RESULTS

A total of 257 adult patients with 275 cases of culture-positive, BCID2-negative BSI were analyzed. Viable organisms were identified in 95.2 % of the cases. False negative results (i.e., in-BCID2 panel target microorganism) occurred at 3.3 % and corresponded mostly to Candida spp. (67 %). Although microorganisms considered of low clinical significance accounted for more than a third of the cases, off-BCID2 panel, clinically relevant microorganisms identified by culture included Bacteroides spp. (other than B. fragilis; 12 %), Clostridium spp. (5.8 %), Candida spp. (4.4 %), Achromobacter xylosoxidans, Pasteurella multocida, Trichosporon asahii, Fusarium spp., Rhodococcus equi, Capnocytophaga spp., and Burkholderia cepacia, among others. Only 116 (42 %) were on appropriate antibiotic therapy at the time of BCID2 result. 30-day mortality was 24 % in the entire cohort, but as high as 33 %, 44 %, and 42 % for Bacteroides spp., Clostridium spp. and Candida BSI, respectively.

CONCLUSIONS

These results highlight the limitations of the BCID2 panel (e.g., need for inclusion of pan-Bacteroides and Clostridium spp., and optimization of sensitivity for Candida spp.); and provide useful insights on the most common causes of BCID2-negative BSI.