Evaluation of the QIAstat-Dx BCID GN and GPF kits for direct identification and antimicrobial resistance prediction from blood culture bottles.

Abstract

Rapid multiplex PCR kits have been used for rapid identification of blood culture isolates and prediction of antimicrobial resistance. We performed an evaluation of the QIAstat-Dx BCID GN and GPF research use only (RUO) kits on positive blood culture bottles using routine laboratory testing as the reference standard. Positive blood culture bottles between November 2023 and January 2024 were tested with QIAstat-Dx BCID GN and GPF kits based on initial Gram stain results and compared against routine identification and phenotypic susceptibility testing. A total of 174 monomicrobial blood cultures were included in the final analysis. The 174 monomicrobial blood cultures composed of 129 BCID GN tests and 45 BCID GPF tests. The majority of on-target Gram-negative organisms in monomicrobial cultures were identified. One Escherichia coli isolate was not identified as such, although the pan-Enterobacterales target was positive. All on-target Gram-positive organisms in monomicrobial cultures were identified. Overall sensitivity and specificity of tem/shv for detection of aminopenicillin resistance in E. coli was 94.7% (18/19) and 95.8% (23/24). The presence/absence of ctx-m and ampC had 100% sensitivity and specificity for identification of third-generation cephalosporin resistance in E. coli and Klebsiella pneumoniae. The combination of blaZ and mecA gene detection was fully predictive of phenotypic susceptibility results to penicillin and cloxacillin for Staphylococcus aureus. Overall, the QIAstat-Dx BCID GN and GPF kits were able to identify on-target pathogens. Detected resistance mechanisms were highly predictive of β-lactam resistance. Prediction of resistance for non-β-lactam antimicrobial was more variable.

Importance: This is one of the first evaluations of the QIAstat BCID kit and demonstrates high levels of correlation for both identification and antimicrobial resistance prediction.