False Negative Escherichia coli Result from the BioFire FilmArray Blood Culture Identification 2 Panel

Misidentification and misreporting of antibiotic resistance in Kluyvera bacteremia by blood culture molecular identification panels

The use of molecular identification panels has advanced the diagnosis for blood stream infections with fast turnaround time and high accuracy. Yet, this technology cannot completely replace conventional blood culture and standardized antibiotic susceptibility testing (AST) given its limitations and occasional false results. Here we present two cases of bacteremia caused by Kluyvera. Its identification and antibiotic resistance were at least partially mispresented by blood culture molecular identification panels on ePlex, Verigene, and Biofire. The detection of CTX-M resistance marker did not align with the susceptibility to the third generation cephalosporins among a wide range of antibiotics for this organism. Conventional extended-spectrum beta-lactamase (ESBL) testing was used to confirm the absence of ESBL. Caution should be taken when managing cases with CTX-M or ESBL detection in blood culture caused by uncommon pathogens. Conventional culture with microbial identification and standardized AST should continue to be the gold standard for routine patient care.

IMPORTANCE

This is the first report that highlights the limitations of blood culture molecular identification panels on identifying Kluyvera and its associated antibiotic resistance patterns. Both the false identification and overreporting of antibiotic resistance could mislead the treatment for bacteremia caused by this pathogen. Patient isolation could have been avoided due to the lack of extended-spectrum beta-lactamase (ESBL) activity of the organism. This report emphasizes the importance of confirming rapid identification and antibiotic resistance by molecular technologies with standardized methods. It also provides insight into the development of new diagnostic panels.

FilmArray (BCID2) provides essential and timely results in bloodstream infections in small acute care hospitals without conventional microbiology services

We have evaluated the performance of FilmArray BCID2 in reactive blood cultures in a small acute care hospital compared to conventional diagnostics at a regional microbiological laboratory. This is a retrospective observational study of BactAlert reactive blood cultures (n = 160) from Helgeland Hospital, July-December 2021, analysed by BCID2 locally and conventional culture at a regional laboratory. The overall clinical and analytic sensitivity with BCID2 were 87.2% and 97.8%, respectively. The false-negative BCID2 rate was low (n = 4; 2.9%). No false-positive BCID2 results were observed. The BCID2 data were available on average 1.88 days earlier than culture-based results, due to long transport time to the regional laboratory. The BCID2 provided results to support a significantly earlier optimized targeted antibiotic treatment in 27% of the cases according to national guidelines for empirical treatment of BSI. The high clinical and analytical sensitivity, and specificity support the use of BCID2 as a robust supplement to traditional cultivation of positive blood cultures. The significant time gain to microbial identification and detection of resistance determinants suggests a great clinical importance of BCID2 in small acute care hospitals with long transport time to conventional clinical microbiology services.