Rapid Direct Identification of Microbial Pathogens and Antimicrobial Resistance Genes in Positive Blood Cultures Using a Fully Automated Multiplex PCR Assay

"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.

Comparative Assessment of Rapid Identification and Antimicrobial Susceptibility Testing Methods for Bloodstream Infections in a Non-24/7 Clinical Microbiology Laboratory

Rapid identification and antimicrobial susceptibility testing are essential for timely bloodstream infection (BSI) management. This study aimed to investigate the performance and turnaround time of multiple rapid diagnostic methods in a microbiology laboratory without 24/7 operation. This study included 236 positive blood culture bottles. Rapid identification methods were assessed with the SepsiTyper kit and the FilmArray blood culture identification 2 (BCID2) panel. Rapid antimicrobial susceptibility testing (AST) methods involved direct AST using the BD Phoenix M50 system and QuantaMatrix direct and rapid antimicrobial susceptibility testing (dRAST) and resistance gene detection with the FilmArray BCID2 panel. Conventional methods were used to compare results. The turnaround time was analyzed from blood culture positivity to preparation initiation and from preparation initiation to result reporting. Both rapid identification methods significantly reduced the turnaround time (~1 day and 19 h) compared to conventional identification. SepsiTyper demonstrated higher species-level accuracy in monomicrobial samples, whereas BCID2 outperformed in polymicrobial cases. Among the rapid AST methods, BCID2 and dRAST enabled result reporting within 24 h of positivity. Preparation delays were >45% of the overall turnaround time. Rapid diagnostics substantially shortened the BSI diagnostic time, even in limited-operation settings. Their clinical utility may be improved through 24/7 laboratory workflows.

Opportunity for early de-escalation of antibiotics in Enterobacterales bacteremia with multiplex PCR rapid diagnostic technology

Gram-negative bacteremia and antimicrobial resistance cause significant morbidity and mortality. Strategies are needed to optimize rapid and effective antimicrobial therapy with early de-escalation. In this brief, we describe the utilization of multiplex polymerase chain reaction rapid diagnostic technology for the early de-escalation of broad-spectrum antimicrobials in patients with Enterobacterales bacteremia.