Rapid detection of Cronobacter spp. with a method combining impedance technology and rRNA based lateral flow assay

Cronobacter spp. is an important release test parameter for powered infant formula (PIF). An impedance method is proposed for the rapid detection of this pathogen in PIF. An impedance based method (BacTrac 4300 Microbiological Analyzer) combined with a RNA hybridisation assay (RiboFlow™) was evaluated using 23 strains in PIF samples and compared to a culture based reference method (ISO/TS 22964). The influences of competitive flora, heat and dry stress on the reliability of the impedance method were investigated. Seven different Cronobacter species were included in the evaluation, among them are strains with high susceptibility to low pH and high temperatures. Compared to the reference method, a higher sensitivity (85%) and specificity (100%) was observed using the impedance method, combined with the commercial rRNA based lateral flow test kit as a confirmation tool. The detection time was substantially shortened by using the impedance technique and RiboFlow™. Cronobacter could be detected within maximally 29 h, while the reference method takes up to five days when including confirmation of positive results.